[PFP#592022365]

STUDY GUIDE FOR

AERIAL APPLICATION PEST CONTROL

The educational material in this study guide is practical information to prepare you to meet the

written test requirements. It doesn’t include all the things you need to know about this

pest-control subject or your pest-control profession. It will, however, help you prepare for your

tests.

Contributors include the Utah Department of Agriculture and Utah State University Extension

Service. This study guide is based on a similar one published by the Nebraska Department of

Agriculture. The information in this manual was adapted from the following sources: Aerial

Application, Cooperative Extension Service, University of Wisconsin. 1993. Aerial Applicator

Training Manual, Cooperative Extension Service, University of Florida. 1992. Pattern Your Ag

Spray Plane, Cooperative Extension Service, University of Arkansas. Agriculture Aircraft

Calibration and Setup for Spraying, Cooperative Extension Service, Kansas State University.

1992. Aerial Application of Pesticides, Cooperative Extension Service, University of Georgia.

1992. Aerial Pest Control for commercial/noncommercial pesticide applicators (category 12):

Aerial Application is a adapted with permission from Iowa Commercial Pesticide Applicator

Manual, Category 11, Aerial Application, published by Iowa State University. Editors were:

Clyde L. Ogg, Extension Assistant, and Larry D. Schulze, Extension Pesticide Coordinator,

University of Nebraska. Special thanks to William W. Lyon, Director of Operations, Department

of Aeronautics for providing valuable comments after reviewing this manual.

The information and recommendations contained in this study guide are based on data believed to

be correct. However, no endorsement, guarantee or warranty of any kind, expressed or implied, is

made with respect to the information contained herein.

Other topics that may be covered in your examinations include First Aid, Personal Protective

Equipment (PPE), Protecting the Environment, Pesticide Movement, Groundwater, Endangered

Species, Application Methods and Equipment, Equipment Calibration, Insecticide Use,

Application, Area Measurements, and Weights and Measures. Information on these topics can be

found in the following books:

1. National Pesticide Applicator Certification Core Manual, Published by the National

Association of State

Departments of Agriculture Research Foundation.

2. The Workers Protection Standard for Agricultural Pesticides – How to Comply:

What Employers Need to Know. U.S. EPA, Revised September 2005, Publication

EPA/735-B-05-002.

These books can be obtained from the Utah Department of Agriculture or Utah State University

Extension Service. Please contact your local Utah Department of Agriculture Compliance

Specialists or Utah State University extension agent.

TABLE OF CONTENTS

INTRODUCTION ............................................................ 1

PESTICIDE LAWS AND REGULATIONS ........................................ 1

APPLICATION EQUIPMENT .................................................. 2

CALIBRATION .............................................................. 7

FIELD OPERATIONS ........................................................ 14

PROPER HANDLING AND USE ............................................... 16

DRIFT .................................................................... 22

THREATENED AND ENDANGERED SPECIES .................................. 27

WORKER PROTECTION STANDARDS ........................................ 27

GROUNDWATER CONTAMINATION STANDARDS ............................. 28

APPENDIX I ............................................................... 29

INTRODUCTION

Aerial application of pesticides offers several

advantages over ground application:

You can cover large areas quickly. You can treat crops

or areas (such as mid-season corn or forest stands) for

which ground equipment isn’t suitable. The application

cost per acre is comparatively low.

To reap the full benefit of these advantages, you and

your client must cooperate to develop a pest-control plan

that will ensure a safe and effective operation. Your

plan must be based on full knowledge of the

pest-pesticide relationship, pesticide activity and

restrictions, and the capabilities and limitations of your

aircraft under prevailing conditions. You must also be

aware of hazards to people, livestock, other crops, and

the environment.

Several factors limit the use of aerial application. These

include weather conditions, fixed obstacles such as

power lines, field size, and the distance from the landing

strip to the target area. Your challenge is to know when

and how you can overcome these limitations and, just as

importantly, when these limitations make aerial

application impractical.

PESTICIDE LAWS AND

REGULATIONS

This part of the manual presents laws and regulations

pertaining specifically to the aerial application of

pesticides. However, when you prepare for and make

such applications, you must understand and comply with

all the pertinent pesticide laws and regulations.

Note that in explaining the following laws, we only

paraphrase the actual laws and rules. You should

consult the laws and rules themselves if you have

questions about them.

FAA REGULATIONS

The application of agricultural chemicals, including

pesticides, from aircraft is regulated in part by the

Federal Aviation Administration (FAA). The regulations

that govern aircraft operations are in the Code of

Federal Regulations, Title 14, Aeronautics and Space.

This code includes regulations that deal specifically with

agricultural aircraft operations.

Before applying pesticides by aircraft, you must have a

valid pilot’s certificate, and you or your employer must

have a valid agricultural aircraft operator’s certificate

issued by the FAA. Also, your aircraft must be certified

as airworthy.

CERTIFICATION REQUIREMENTS

You must be certified in the Aerial Pest-Control

Category prior to commercially applying pesticides in

Utah.

Aerial pesticide-application operations conducted in

Utah must be certified by the Utah Department of

Agriculture.

Certification in this category includes applicators

applying pesticides by aircraft to control agricultural,

forest, health- related, or any other pests. Applicators

are also required to be certified in categories of

intended application.

HANDLERS

You must make sure that employees who mix or load

pesticides into your aircraft have had appropriate

pesticide-safety training. Such employees must be either

certified as applicators or have received pesticide-safety

training for pesticide handlers as required under the

Worker Protection Standard (WPS).

Anyone who is certified as a pesticide applicator in any

commercial category or as a private applicator or who

has been trained as a pesticide handler according to the

requirements of the WPS may mix or load pesticides.

Such a person would require certification in the Aerial

Pest-Control Category only if he or she intended to

apply pesticides aerially in addition to mixing or loading

pesticides.

PESTICIDE OVERSPRAY AND

DRIFT

Pesticide overspray is defined as applying pesticide

beyond the boundaries of the target area. Overspray is

considered an inherently negligent action that

can’t be excused under any circumstance; it’s flatly

prohibited.

Pesticide drift, like overspray, often implies a lack of

proper care on the part of the pesticide applicator. Drift

is defined as the movement of pesticide in air currents or

by diffusion onto property beyond the boundaries of the

target area. Applicators are responsible for confining

pesticide applications to the target area and for taking

precautions to prevent other persons or their property

from being exposed to the pesticide you are applying.

APPLICATION EQUIPMENT

Equipment for aerial application of pesticides must be

able to lift, transport and disperse pesticides safely and

accurately to the target area. You need to understand

how your equipment affects the application so that you

can ensure effective treatment under any conditions you

encounter.

CHOICE OF AIRCRAFT

You can apply pesticides aerially using either a fixed-

wing airplane or a helicopter, although most applicators

use airplanes. Airplanes are fast, maneuverable, and

have a large payload capacity per dollar invested.

Helicopters are even more maneuverable, can be

operated over a range of speeds, and may be operated

in almost any area because a regular landing strip isn’t

needed. However, helicopters are more expensive to

operate per unit of flying time, so the pilot must minimize

the time lost in turnarounds and refilling.

DISPERSAL SYSTEMS

Metering of spray material is a key function of all

agricultural aircraft dispersal systems. Metering and

dispersal equipment must deliver the labeled rate of a

liquid or solid pesticide accurately, uniformly, and in a

short period of time.

LIQUID DISPERSAL SYSTEMS

Liquid dispersal systems are the most widely used in

agricultural aviation. They consist of a hydraulic circuit,

including a tank, pump, hose, pressure gauge, boom,

screens, flow regulators and nozzles. More and more

applicators are finding that flow meters are valuable in

monitoring system output and improving application

performance.

Dispersal systems may be wind-driven or powered

directly from the aircraft engine.

A typical system is shown in Figure 1.

Figure 1. The components of a liquid dispersal

system on a Piper Brave airplane.

Tank or Hopper

The tank should be corrosion-resistant; most are made

of fiberglass. Most tanks can be filled through an

opening in the top. However, it’s preferable to fill

through a pipe, equipped with a quick-coupling valve,

which comes out the side of the fuselage. The tank

should also have a large emergency gate through which

the load can be dumped in a matter of seconds. The

aircraft must have a gauge that measures tank contents.

The tank should have an air vent that will prevent a

vacuum from developing that would alter or stop the

normal flow of the liquid. Tanks are also fitted with

baffles to limit the sloshing of liquid during flight.

Airplane spray tanks. On an airplane, the tank is

usually mounted in front of the cockpit and as close as

possible to the center of gravity of the plane so that the

trim won’t be affected as the tank empties.

Helicopter spray tanks. The spray tanks on

helicopters are usually mounted in pairs on each side of

the fuselage. A pipe connects the tanks so that the spray is usually low (in the 20 to 50 psi range), and a high flow

is drawn equally from both tanks to keep the helicopter rate is required even for relatively low application rates

balanced. The tanks on most helicopters used in aerial because the number of acres sprayed per unit of time is

application have relatively small capacities in comparison high.

to airplane tanks.

Pumps

The pump is necessary to ensure uniform and proper

flow rate, produce the desired atomization from nozzles,

and maintain suspensions. The majority of pumps on

airplanes are powered by a fan mounted under the

aircraft in the slipstream of the propeller. Many fans are

equipped with variable-pitch blades so the pump speed

can be changed. Pumps must be able to produce the

desired nozzle pressure (plus five psi for friction loss in

the line) to handle nozzle output and agitation

requirements. Air shear across the nozzle pattern helps

break the liquid into spray, so high pressure isn’t

required for atomization.

Carefully consider the size of the pump. A pump with

too little capacity will require reducing the swath spacing

to assure adequate deposition on the crop. If you use a

centrifugal pump that has a capacity much greater than

required, the impeller may cavitate; this allows air into

the system and calibration becomes erratic.

Centrifugal pump. The pump most widely used for

spraying is the centrifugal pump (Figure 2). It’s available

in many sizes, handles all kinds of liquid formulations

with minimum wear, and can be operated without a

pressure-relief valve.

Figure 2. A centrifuge pump.

Centrifugal pumps that deliver a high flow rate when

using a low operating pressure are generally used. Such

pumps are preferred because the spray-system pressure

Rotary gear pump. If high pressures are needed, a

rotary gear pump is often used (Figure 3). Gear pumps

deliver a low flow rate, but can produce as high as 200

psi. Gear pumps that deliver the gallons per minute

needed for most aerial spraying jobs weigh much more

than a comparable centrifugal pump. A pressure-relief

valve or bypass must be incorporated into the spray

system to relieve the pressure or bypass the chemical

when the spray valve is turned off. Gear pumps are

subject to excessive wear with certain formulations such

as wettable powders. For these reasons -- extra weight,

rapid wear when pumping abrasive formulations, and the

need for a pressure relief valve -- gear pumps are used

only where high pressure is needed.

Figure 3. A rotary gear pump.

ULV applications. Ultralow volume (ULV)

applications (0.05 to 0.5 gallons per acre) need only a

minimum- capacity pump. If your aircraft will be used

only for ULV spraying, use a small centrifugal, gear, or

other rotary pump that can provide the required flow

rate at 40 psi to assure uniform flow and optimum nozzle

performance.

If your aircraft is equipped for high-volume spraying and

you want to do ULV spraying too, a minor modification

will be required. Many high-volume pumps are capable

of pumping 75 gallons per minute. ULV applications

may require only 2 gallons per minute. Bypassing 73

gallons back into the spray tank will aerate the spray

solution or cause excessive foaming of some materials.

In either case, accurate calibration of the spraying

system is impossible.

Installing a modification will make it possible to use the orifice size and materials being applied. The 20-mesh

same spraying system for high-volume and ULV screens have the largest openings and would be used

applications. with nozzles having a relatively large orifice. Nothing

Agitation System

Many pesticide formulations require some form of

agitation during application to maintain the spray

mixture.

Recirculation of the spray mixture during ferrying to the

worksite and during turnarounds is usually enough.

When the aircraft is used to treat long fields where

turnarounds are limited, the pump must have sufficient

capacity to supply the boom and provide adequate

bypass agitation. The return flow should wash the

bottom of the tank to help prevent settling of pesticide

residue.

Plumbing

Aerial spray equipment must be designed with valves,

piping, fittings and screens that are big enough for rapid

dispersal of spray material.

Piping and fittings. Main piping and fittings should

have a large diameter (up to three inches) to apply high

volumes of liquids and a smaller diameter (about one

inch) for low-volume application; smaller piping can

often be used with helicopters because their slower

speed makes it possible to get by with lower flow rates.

The piping must be able to handle the pump pressure.

Hoses should be large enough to carry the desired flow

and should be corrosion-resistant. They are less likely to

blow off if the ends of the tubes are beaded or double-

clamped. Avoid sharp bends in hoses as much as

possible, and change hoses when they swell or develop

surface cracks.

Screens. Correctly sized line and nozzle screens must

protect components from damage and nozzles from

clogging. The screens should be cleaned daily during

spray operation or whenever flow or pressure indicates

clogging.

Nozzle screen sizes of 20 to 100 mesh or an equivalent

slotted strainer should be used, depending on nozzle

finer than 50-mesh screens should be used with wettable

powders.

Line screens should be of coarser mesh than nozzle

screens and should be located between the tank and

pump and/or between the pump and boom. Locating the

line screen between the tank and pump will protect the

pump from damage; this screen, located in the suction

line, should have large mesh openings.

Figure 4. A positive cut-off spray valve.

Valves. Use a positive cut-off valve in the line to

eliminate dripping when shutting off the spray at the end

of the runs or when flying over pastures, lakes, streams,

and other sensitive areas. A positive cut-off valve that

incorporates the suck-back feature (Figure 4) reduces

the risk of dripping nozzles. (Nozzle check valves will be

discussed later.) Suck-back is lost if the tank is empty or

the pump is off.

Pressure gauges. Attach the pressure-gauge sensing

line near or at the boom to more accurately determine

nozzle

pressure. The ideal location for the pressure gauge is in

a position where you can easily monitor pump

performance from the cockpit. Because the flow of the

liquid is related to the pressure, the pressure should be

maintained throughout a spraying operation. Pressure

gauges can malfunction or the sensing line can partially

plug. Check gauges periodically against a gauge you

know is accurate.

Pressure gauges are obviously valuable instruments for

monitoring pump and nozzle performance. However,

don’t rely solely on pressure gauges to calibrate an

aircraft. Nozzle manufacturers' tables give the gallons type. For ULV applications, flat-fan nozzles or rotary

per minute of water emitted by a particular nozzle at atomizers are often used.

various pressures, but the actual output will vary from

aircraft to aircraft. An applicator who calibrates an Position the nozzles (and booms) so the spray won’t

aircraft using nozzles and pressure settings from catalog strike any part of the aircraft or the boom attachments.

values will often be in for a surprise. Field checking your If the spray does strike any structural member of the

aircraft's spray output and pattern is always advisable. aircraft, it will:

Booms

The boom supports nozzles along the wingspan of an

airplane. It may be round, airfoil-shaped or streamlined.

Booms should be located behind and below the trailing

edge of the wing to reduce drag and to place the nozzles

in cleaner airflow. Drop booms are often used to help

keep nozzles in clean air. Research shows that the lower

position is likely to give a better deposit pattern. End

caps for booms should be removable for cleaning.

A boom about three-fourths as long as the wingspan is

preferable, because nozzles placed farther toward the tip

have a large amount of their output entrained in the

wing-tip vortex and contribute to drift problems.

Location of outboard nozzles on booms is critical,

because wing tip and main rotor vortices (discussed in

the next section) influence pattern width and drift.

Research has shown that nozzles placed outboard of the

three-fourths wingspan point contribute little toward

increasing swath width.

Nozzles

In ground application, the spray pattern from each

individual nozzle is a major factor in distributing spray

uniformly across the swath. In aerial application, spray

distribution across the swath is affected considerably by

aircraft wake; thus, it’s the overall pattern of all nozzles,

rather than the individual pattern of each nozzle, which

is important. Therefore, nozzle features affecting spray

droplet size, droplet distribution, flow rate, and tendency

to clog are more critical than they would be for a ground

sprayer.

Usually, the same nozzle tips, discs and cores, caps and

screens are used on both aerial- and ground-application

equipment. The most commonly used spray system for

higher application rates is a boom with hydraulic cone

nozzles. The cone nozzles used most often in aerial

application are the disc-core type and the whirl chamber

! Collect and fall off in large drops.

! Distort the spray pattern.

! Waste material.

! Cause corrosion of aircraft parts.

Ideally, the boom should have an end nozzle. However,

if the outermost nozzle isn’t at the end of the boom,

make provisions to purge the air trapped in the outer

ends of the boom. Trapped air will cause the spray to

continue flowing after the spray valve is closed. To

eliminate trapped air, use a tee to attach each outboard

nozzle to the boom and connect a small bleed line from

the tee to the end of the boom. This will ensure rapid

filling of the boom, immediate flow from each nozzle,

and quick and positive cutoff when the spray valve is

closed.

Rotary atomizers. Rotary nozzles allow you more

control over the size of the droplets released. Spray

droplets are formed by toothed, grooved, spinning discs

or cups. Centrifugal force generated by the spinning

action causes the release of spray droplets. The speed

at which the nozzle turns and the liquid flow rate control

the size of the droplets. Rotary nozzles reduce the range

of droplet sizes being applied, so very small and very

large droplets are eliminated. However, they can

generate a range of droplet sizes, enabling you to use the

same nozzles for coarse or fine sprays. Control of

droplet size with rotary spray nozzles is especially

significant when oil carriers are used.

Rotary nozzles can apply a wide range of application

rates. Because they have a relatively large metering

orifice, these nozzles don't clog as easily as conventional

nozzles when applying low-volume sprays with a high

concentration of chemicals in suspension.

You may need to fly up to 25 feet above the target to

obtain a uniform deposit pattern. Uniformity also

depends on how fine the spray is and the spacing of the

nozzles. For low-level work, six or more nozzles are Dry materials are dispensed from an airplane hopper

required to provide a uniform swath. through a spreader mounted below the fuselage. The

Microfoil boom A microfoil boom can be used on

helicopters to control droplet size. It’s most often used

for treating rights-of-way. This boom consists of a series

of six-inch-long, airfoil-shaped nozzles. Sixty needlelike

tubes project from the trailing edge of each nozzle.

Spray pressure and orifice diameter control droplet size.

Droplets are formed on the needlelike tubes and pulled

off by the airstream, then they enter the non-turbulent

air behind the nozzle. The microfoil boom is specifically

designed for helicopters, because droplet size can’t be

maintained at high speeds. It can’t be used for

high-viscosity sprays or wettable powders, because the

orifices tend to clog.

Figure 5. An anti-drip nozzle system.

Nozzle anti-drip device. Equip each nozzle with a

check valve to prevent dripping when the spray is shut

off. The diaphragm check valve is the most widely used

type (Figure 5). When the pressure drops to about seven

psi, the spring force is greater than the hydraulic force

on the opposite side of the diaphragm, and the

diaphragm closes off the hole in the barrel leading to the

orifice. These check valves must be used in combination

with in-line valves that have the suck-back feature to

prevent dripping. In systems where suck-back is

unavailable such as on helicopters, a 15-pound spring is

commonly used.

Clean check valves often. If you use diaphragm check

valves, change the diaphragms at regular intervals.

DRY (GRANULAR) DISPERSAL SYSTEMS

hopper walls should slope enough to ensure uniform flow

of material to the spreader. The hopper should be vented

properly to ensure a more uniform flow, especially when

the hopper and loading door have airtight seals.

The gate that controls the flow of material from hopper

to spreader should move freely, provide a tight seal to

prevent leakage when closed, and provide a uniform

flow to all portions of the spreader. Inspect the gate

often to make sure it doesn’t allow leaks.

The hopper should be equipped with an agitator when

sticky, lumpy or fine (less than 60-mesh) materials are

to be dispersed. A properly designed and functioning

agitator promotes uniform flow of the hopper contents.

Dispersal systems for applying pesticide granules are

primarily ram-air spreaders for airplanes and centrifugal

or fan-powered air-flow spreaders for helicopters.

Ram-air spreaders. The same hopper that is used to

hold the liquid spray is used to hold dry materials when

they are spread with an airplane. Ram-air spreaders

(Figure 6) are mounted under the belly of an aircraft in

such a manner that they can be quickly removed when

the aircraft must revert to spraying.

The amount of dry material fed into the ram-air spreader

is determined by the opening in the metering gate

between the hopper and spreader. Ram-air spreaders

have internal vanes that impart a sidewards velocity to

the air that enters the throat of the spreader. This

feature increases the effective swath of the spreader.

Ram-air spreaders can uniformly spread material over

a limited range of application rates. When too large an

amount of dry material is metered into the spreader, the

spreader becomes choked off and less air is able to

enter the unit. A large amount of dry material entering

the spreader requires more air, not less, to convey the

material through the spreader and achieve a wide,

uniform swath.

Figure 6. A ram-air spreader for applying

materials by airplane.

Ram-air spreaders have a number of drawbacks, such

as the limited range of application rates. They adversely

affect aircraft performance because of the high drag

load resulting from their unavoidably being placed in the

high-speed airstream, though some new spreaders have

less drag than the pump and booms produce. However,

ram-air spreaders have survived a long list of “new,

improved designs” because they are simple, versatile,

and reasonably priced and do a fairly good job of

spreading dry materials.

Centrifugal spreaders commonly used by helicopters

are self-contained units having their own hoppers. The

unit is suspended from the helicopter by a cable and

hook (Figure 7). The spinners that the dry material is

metered onto are usually driven by a hydraulic motor

and, in some cases, by an integral gasoline engine.

Figure 7. A centrifugal spreader for applying dry

materials by helicopter.

The units are controlled with hydraulic control cables or

radio frequency. Usually, two self-contained units are

used so that the pilot can spread with one while the

other is being refilled.

CALIBRATION

Dispersal equipment you use must be accurately

calibrated in order to perform any operation. The best

pilot flying the best aircraft can’t properly treat an area

if the equipment dispenses the incorrect amount of

material in a variable pattern. Proper calibration not only

helps ensure effective treatment, but it also helps

prevent pesticide drift. Improper calibration, on the other

hand, will result in dissatisfied customers and perhaps

even an angry public.

(Note: Some formulas used in this unit contain numbers

that are constants, numbers that remain unchanged

whenever you use the formula. To make calibration

easier for you, we provide you with the constants rather

than going through the complex calculations from which

the constants are derived.)

BASIC FORMULAS FOR

AIRCRAFT CALIBRATION

Calibration is used to determine how much liquid solution

nozzles must deliver to deposit the required amount of

product active ingredient (AI) per acre. Only changes in

ground speed or flow rate can change the amount of

material an aircraft applies. Never use swath width to

change the application rate without physically changing

the nozzle configuration. The basic steps of aircraft

calibration are:

STEP 1

A. Determine the acres your aircraft system treats per

minute at the speed and estimated swath width you plan

to fly. The effective swath width should match that

determined by pattern testing.

Equation 1: Acres per minute

.00202 X swath width X speed = acres per minute

Example using 60-ft. swath width and 120 mph:

.00202 X 60 ft. X 120 mph = 14.54 acres/minute Based on this calculation, select a nozzle that has a flow

B. Determine the gallons you must spray per minute to to 30 psi.

apply the recommended gallonage rate.

Equation 2: Gallons per minute

Acres per minute X application rate = gpm

Example using 10 gallons per acre:

14.54 a/min. X 10 gpa = 145.4 gpm

C. Once you have determined the flow rate, select the

nozzle orifice size and number of nozzles needed to

deliver the correct number of gallons per minute within

the allowable operating-pressure range of your system.

It’s generally recommended that spray pressures

remain greater than 18 psi and less than 40 psi

(preferably 18 to 30 psi to minimize drift).

STEP 2

Determine the number of nozzles to use. Assume you

are using a nozzle with a flow rate of 3 gpm at 25 psi.

Equation 3: Nozzles needed

Total flow ÷ gpm per nozzle = number of nozzles needed

145.4 gpm ÷ 3 gpm per nozzle = 48.46 nozzles needed

To obtain the desired application rate at a three-gpm

flow rate, you would need 48 operating nozzles. Position

each nozzle and test the system pattern to verify

distribution pattern uniformity and required nozzle-

pattern changes.

STEP 3

Determine what nozzle tip size to use. For this

calculation, you must select the total number of nozzle-

outlet positions on the boom or the total number of

positions before calculations begin. Assume that 66

nozzles are needed.

Equation 4: gpm per nozzle

Total flow ÷ number of nozzles = gpm per nozzle

145.4 gpm ÷ 66 nozzles = 2.2 gpm per nozzle

rate close to 2.2 gpm in the desired pressure range of 18

Once individual nozzles are mounted on a boom system,

calculating flow rates is hard, especially if you’re

equipping an aircraft for high application rates. Individual

nozzle flow rates vary depending on location, turbulence

in the boom, and the number of boom restrictions. After

you place the nozzles on the boom, make a trial run to

be sure you are applying the correct rate and depositing

the spray uniformly.

A high number of larger nozzles (larger orifices) results

in high fluid velocities inside the boom and a large

pressure drop from the center of the boom to the end of

the boom where the last nozzle is located. This pressure

differential may result in narrower effective swath

widths. Full three-inch liquid systems (no restrictions

smaller than three inches from the pump outlet on) are

recommended for field applications greater than nine

gpa. The exact flow rate (gpm) or pressure (psi) needed

for a particular nozzle may not be listed in the available

tables. If you know the flow rate at one pressure, you

can calculate the pressure or flow rate for other

pressures or flow rates by using the following equation:

Equation 5: Flow rates and pressures

gpm ÷ gpm = square root of psi ÷ square root of psi

1 2 1 2

If you know the desired pressure, you can calculate the

unknown nozzle flow rate by rearranging the above

equation as follows:

Equation 6: gpm at desired pressure

(square root of gpm known) X (square root of psi

desired) ÷ square root of psi known = gpm unknown

Or, if you know what flow rate you want, you can find

the pressure you need by rearranging Equation 6 as

follows:

Equation 7: Pressure at desired gpm

[(gpm desired X (square root of psi known) ÷ (gpm

known)] = psi unknown

This relationship between pressure and flow rate is

accurate for most hydraulic nozzles.

For example, if you use 6530 flat fan tips in step 3 When you evaluate the pattern and determine the

above, and the nozzle catalog lists the flow rate of this effective swath of an aircraft, then spray height, speed,

nozzle at 40 psi as 3.0 gpm, you can calculate the spray pressure, and nozzle location should duplicate field

needed pressure as follows: conditions. The best time for testing is early in the

[(2.2 gpm X square root of 40 psi) ÷ 3.0 gpm] = 21.51 thermal turbulence. Fly the plane directly into the wind

psi and limit testing to days when the wind speed is less

Using equation 7, you would find that the pressure

needed to provide a flow rate of 2.2 gpm with this nozzle Pattern-testing is such an important part of achieving

is 21.51 psi. This is within the acceptable range for this good aerial application that computerized pattern-testing

nozzle. equipment has been developed for this purpose. One

The above calculation assumes that all nozzles receive of fluorescent dye that an aircraft sprays onto a 100-foot

the same pressure. This is usually not the case, long paper tape or cotton string in the field. The dye

especially on higher volume applications. Pressures intensity is recorded by a computer that gives a relative

often have to be increased about ten percent to reading of intensities and also determines the swath

compensate for flow restrictions and pressure loss along spacing that would yield the best pattern uniformity for

the boom. the pattern on the tape being analyzed.

Install inboard and outboard pressure gauges to check Computerized pattern-testing equipment may be too

for significant (one to two psi or more) pressure drops expensive for you to buy for personal use. However,

along the boom at high flow rates. Switch gauge you can get an idea of the pattern applied by your

positions to check for gauge error. Make a trial run to be aircraft by using the general layout shown in Figure 8 to

sure the aircraft is dispersing the desired application pattern-test. This figure shows a layout used for pattern-

rate. testing dry materials. For liquids, use a continuous piece

PATTERN TESTING FOR LIQUIDS

Perhaps the greatest difference between calibrating air

and ground application equipment is how you ensure that

the pesticide is applied uniformly over the target area.

Ground-equipment nozzles are spaced uniformly along a

boom in an attempt to get the same output and spray

pattern from each nozzle. The pattern doesn’t vary

drastically among different pieces of application

equipment.

In aerial application, the very movement of the aircraft

causes differential airflow across the length of the

boom. Thus, the pattern of an individual nozzle, tested at

no movement, is of minor importance to the overall

distribution of the applied pesticide. Droplet size, droplet

distribution, flow rate, and tendency to clog are very

important factors. For these reasons, no standard

configuration of nozzles along a boom provides uniform

distribution. The ideal configuration varies with each

aircraft (even the same model aircraft), delivery system,

and application rate.

morning before the sun heats the ground and causes

than ten mph.

system consists of a fluorometer that reads the intensity

of adding machine paper or water-sensitive cards rather

than evenly spaced collection pans. (We will discuss

pattern-testing for dry materials later in this section.)

The pattern line should be at least 80 feet long.

Determine the wind direction, and place flags about 100

yards on each side of the pattern line along the flight

path (center line).

Figure 8. General layout for testing deposition

pattern when calibrating aircraft.

Regardless of which testing system you use, make sure

that the boom and all nozzles, screens, and other parts of

the spraying system are clean and rinsed before you test

the aircraft. Fill the spray tank with about 30 gallons of

water, and add enough water-soluble dye to make a

dark solution. Fly a short pass to purge the boom of any

clear water and check for leaks.

You could also do this on the ground by attaching a

garden hose to the end of the boom. The hose, using

external pressure, will force water containing dye

through the boom and out of the nozzles. Turn off the

hose and see if any nozzles continue to drip after the

pressure is off. The dye will make any leaks or plugged

drop-pipes easy to spot. Figure 9. Effective swath width of a typical

After takeoff, purge the boom and make sure that dye

leaves the end nozzles. Align the aircraft with the flags

on a spray run that duplicates the actual field practices.

Spray at least 100 yards on both sides of the pattern line

while maintaining straight and level flight to ensure a

representative spray pattern. Repeat the test to make

sure the run was representative of typical spray

deposition.

Visual evaluation requires some experience, but you

should be able to identify common problems with spray

uniformity and swath width. Watch for light drop-density

areas around the centerline and uneven densities toward

the wing tips.

The effective swath width will be considerably narrower

than the distance between the outside samples where

dye is evident (Figure 9). The amount of dye is

reasonably constant for some distance on each side of

the flight path and then begins to reduce until there is no

dye evident. The effective swath width is the distance

between the two points on the sloping ends of the

pattern where the dye level is one-half the amount at the

beginning of the slope.

deposition pattern.

FACTORS THAT AFFECT DISPOSITION

PATTERN

A number of factors influence swath width and

application uniformity. Some, such as wing tip or rotor

vortex, result from equipment design and must always

be taken into consideration. Others, such as nozzle

problems, are maintenance problems that can be

corrected. You can detect each of these problems with

pattern testing. Next we will discuss how to diagnose,

compensate for, or correct these and other common

causes of non-uniform spray deposition.

Leaks. The dye makes it relatively easy for you to

detect system leaks. If there are indications of system

leaks, such as very large drops of dye on the paper used

for pattern evaluation, check the spray system

thoroughly.

Nozzle problems. It’s normal for small and large

droplets to appear on the sampling paper when pattern

testing, because all atomizers generate a range of

droplet sizes. If the range of droplets varies

tremendously between locations in the pattern, different-

sized or badly worn nozzles may be the problem. (You

will generally find finer droplets in the center of the

pattern that are caused by the increased shear action of

the high-speed prop blast.)

Sometimes, you may put different-sized nozzles on the

boom on purpose. For example, you may use a few

nozzles with larger openings to counter prop wash

displacement. Nozzle wear usually doesn’t affect spray speed, and special cowlings such as speed rings, spray

pattern significantly. You are likely to notice that you are droplet size, and spraying height.

spraying too great a volume before the wear gets bad

enough to have a significant impact on the pattern. Helicopters exhibit similar rotor-wash characteristics.

Incorrect droplet spectrum. It’s impossible to

determine the size of droplets that are generated by an

atomizer by measuring the droplet stain on the sampling

paper. However, an experienced operator can determine

whether droplet size is appropriate for the job to be

done. Generally, coarse droplets are used for applying

herbicides, small to medium for insecticides, and small

for fungicides.

EFFECTS OF EQUIPMENT DESIGN AND

CONFIGURATION

Airplanes and helicopters must move air to fly. The

resulting air movement isn’t uniform, but it’s somewhat

predictable. Your challenges are to understand how air

moves around and under the aircraft and to compensate

for this movement in order to apply pesticides uniformly

across the swath.

Again, although we mention some general guidelines for

producing a uniform spray pattern, remember that the

actual placement of nozzles varies with each individual

aircraft. There’s no standard configuration of nozzles

that will provide a uniform pattern.

Prop and rotor wash. Prop-wash turbulence, which is

the result of the clockwise propeller air helix spiraling

into the fuselage, carries droplets from nozzles to the

right of the fuselage and deposits them on the target

located beneath or to the left of the fuselage.

Counterclockwise-rotation propellers (used with

counterclockwise-rotating engines such as the PZL)

have similar but reversed prop-wash problems, with the

excess deposit on the opposite right side of the aircraft.

Prop wash results in a lack of spray deposit reaching

targets from the center to about six feet right (or left in

the case of the PZL engines) of the fuselage.

Historically, a high percentage of the aircraft tested

during aerial- application workshops have required

compensation for this problem. The seriousness of prop-

wash spray shift depends on factors that include aircraft

fuselage and aerodynamics, propeller length and rotation

The rotation of the rotor creates a swirling, cone-shaped

helix that descends, trailing the direction of flight. This

rotating air mass traps small spray droplets and

transports them, resulting in a distortion of the spray

deposit away from the leading rotor and in the direction

of the trailing rotor. This shift may be influenced by

many factors, including aircraft aerodynamics, location

of boom mounting, spray droplet size, forward flight

speed, and weight of the aircraft.

Prop wash is anticipated in propeller aircraft, especially

those with larger radial engines. Some compensation is

possible if nozzles are located correctly. Install extra

nozzles to the right of the fuselage, in line with or just

inboard of a point directly behind the center of the

propeller.

To determine this point, align the propeller horizontally,

and visualize a line parallel to the line of flight rearward

to the spray boom. Radial-powered Ag Cats typically

require more nozzles on the right than other types of

aircraft. Engine speed rings alter the airflow around the

engine and result in different distortions to the deposition

patterns than the same aircraft without a speed ring.

The deposition pattern of the large Melex Dromader

aircraft is especially sensitive to the addition of third-

party-manufactured speed rings. After adding or

relocating any nozzle position, pattern-test the aircraft to

verify the change in deposition uniformity (Figure 10).

Wing-tip vortex. Wing-tip vortex originates in the

turbulence behind the wing as the airstream moves

quickly from the high-pressure area under the wing and

meets the low-pressure air from the top of the wing

surface. The air mass travels the shortest route, which

causes part of the air to slip outward from under the

wing and introduces a large amount of turbulence and

rotation. Visualize this rotation as a spinning cone of air

with the highest velocities toward the center of the cone.

The highest-velocity (strongest) vortex action is

produced by heavy, slow-moving aircraft. Bi-wing

aircraft produce vortices at each of the wing tips that

quickly combine into a single vortex behind the aircraft.

The combined vortex is about equal in strength to that

produced by a monowing aircraft of the same weight

and air speed.

Figure 10. Effect on spray pattern caused by Placing nozzles inboard and/or below the trailing edge of

propwash and wing-tip vortices. the wing reduces the amount of spray trapped in the

Larger droplets released inboard and well below the wing aircraft indicates that removing nozzles inboard

wing are least influenced by the wing-tip vortex. Wing- from the wing tips until a ten-percent reduction in

down wash airflow causes the pattern spray to spread. effective swath width is noted reduces potential driftable

Wing-tip vortices are also partially responsible for a

swath wider than the aircraft wingspan. However, spray Fly-in pattern-testing has verified that drift-hazard

must enter only the outer, gently swirling air during its reduction is maximized by not placing a nozzle within six

second or third rotation rather than the eye of the to ten feet of the wing tip. Normally, the swath width of

vortex. The outer portion of the vortex has a downward conventional aircraft isn’t reduced by reducing the boom

and outward motion that carries primarily the smaller length to 70 or 75 percent of the wingspan. The effect

droplets down to the crop outside the wingspan. The eye of reducing boom length more than 70 percent depends

of the vortex traps all but the largest droplets and rotates on the aircraft, nozzle pressure, and spray-droplet size.

them above the aircraft wing level. These droplets may

be suspended long enough that the pesticide carrier Applicator tests using rotary nozzles (that is, Micronair)

(water) evaporates or moves off target (Figure 11). indicate that the outermost nozzle position may be

Helicopters produce rotor vortices in much the same wingspan to ensure that material isn’t entrained in the

way as fixed-wing aircraft, except that the rotor blade wing-tip-vortex circulation.

changes the angle of attack as it travels around in a

circular path. The rotor vortices form just below and Nozzle stoppage, improper swath width, and other

behind the blade tip. The maximum strength exists factors can cause poor distribution. Strips of poor weed

where the rotor blade is at the highest angle of attack. control, called streaking, indicate poor distribution.

Place nozzles inboard of the rotor-blade tips to help problem from field results occurs strictly by chance.

prevent entrainment of the spray in the vortex. Toe-

mount booms produce less rotor distortion than do skid- If you wait for problems to show up in a field situation,

or heel- mounted booms. the damage has already been done and is hard to

Figure 11. Wing tip vortex zones where smaller

droplets can become trapped (droplet diameters

shown in micronsF).

vortex circulation. Recent NASA research on fixed-

lines by up to 90 percent.

positioned inboard as much as 55 percent of the

However, identifying the cause and remedying this

remedy. Complete pattern-testing and make calibration

adjustments to the aircraft to obtain uniform deposition [(acres per mile) X 60] ÷ seconds to fly 1 mile = acres

before you make annual applications. per minute

CALIBRATION CALCULATIONS

FOR SOLIDS

Give equal attention to calibrating equipment that

dispenses solids and liquids. The type of spreader, type

of granular material, rate per acre, and amount of swath

overlap all affect calibration accuracy. If one condition

changes, you must repeat the calibration procedure. For

example, the size, shape, density and flowability of a

granular material affects the swath width, application

rate and pattern. Also, except at low rates, swath width

is inversely proportional to application rate; that is, if you

increase the rate, you decrease the swath width.

If the spreader manufacturer provided an owner's

manual that specifies gate settings for different delivery

rates and for different formulations, use this data as a

starting point. Determine the actual pounds per minute

by conducting a hopper-refill test during the application

of the first few swaths of material. (Hopper-refill tests

are discussed later in this section.)

Assume a swath width based on previous experience

with similar equipment. Once you know the flying speed,

you can calculate the desired rate per minute.

Equation:

3600 ÷ mph = seconds to fly 1 mile

Example:

If you assume a speed of 90 mph and a swath width of

50 feet:

3600 ÷ 90 mph = 40 seconds

Equation:

Swath width (feet) ÷ 8.25 = acres covered per mile

Example:

50 ÷ 8.25 = 6.06 acres per mile

You can then calculate acres per minute as follows:

Equation:

Example:

(6.06 X 60) ÷ 40 = 9.09 acres per minute

If the label calls for 10 pounds per acre, the desired flow

rate is:

Equation:

(pounds per acre) X (acres per minute) = pounds per

minute

Example:

(10) X (9.09) = 90.9 pounds per minute

If you don't have information regarding proper gate

settings, do some preliminary work on the ground. Time

the flow of 100 pounds of granules through the gate

opening. The flow rate will be about twice as fast during

flight; use this to make an estimate, and adjust the gate

for the desired rate per acre.

For example, suppose in your ground test, it took two

minutes for 100 pounds to flow through the gate

opening. That would correspond to 100 pounds per

minute while in flight. This output is too high; readjust

the gate opening and try again. When the value obtained

in the ground test is acceptable, check the distribution by

doing a test run.

PATTERN TESTING FOR DRY MATERIALS

You can determine the distribution pattern only by

setting out pans across a line of flight. The setup is

similar to that shown for liquid sprays in Figure 8 on

page 14. The pans should be at least four inches deep

and padded inside with a thin layer of foam. The inside

area should be sufficient to catch a measurable amount

of material. (For example, a 16-square-foot pan will

catch up to half an ounce if you apply granules at 100

pounds per acre.) Place them at two-foot intervals for

20 feet on each side of the swath centerline and at

five-foot intervals for an additional 30 feet on each side.

Do this on flat ground, and be sure the total width is

greater than the expected swath width.

Perform the test during minimum wind conditions. Orient

the pans at right angles to the wind and fly into the wind.

Fly at 30 to 50 feet above the ground surface, which is 6 units. Likewise, the two swaths applied a total of 6

normal for granular applications. units (3 + 3) at point C. Thus, a distributor with a

DETERMINING SWATH WIDTH

After the run is completed, move from one end of the

test strip to the other, collecting the granules from each

pan, and transfer them into a small-diameter glass tube

(test tubes do nicely). Use a separate tube for each pan

and keep the tubes in order.

When you’re finished, place the tubes in sequence on a

wooden base to display distribution visually. Use the

display to determine the shape of the distribution curve

and estimate the overlap you need in order to provide

even coverage.

Your estimate will be more accurate if you plot the

height of the granules in each tube, in sequence, on a

piece of graph paper. If necessary, cut out the graph,

duplicate it, and align the two to give the most uniform

distribution; 50 percent overlap is common. The

effective swath width is the total width minus the

distance of overlap.

Figure 12. Triangular deposition pattern of dry These examples show that you can’t just fly two swaths

material across a swath. over the collection pans and take half the distribution

The distribution shown in Figure 12 is an idealized point on a single pass and determine the pattern and

plotting of the amounts caught in the pans laid out across swath from the plottings of multiple passes. After you

60 feet. This triangle is a perfect pattern for a 30-foot achieve an even pattern, you can determine the swath

swath spacing. Another pattern centered around a point width and calculate the rate per acre.

30 feet from the first flight path would result in an even

distribution between the two patterns. The examples of the triangle and trapezoid patterns cited

Figure 12 shows that at point A, 6 units (pounds or other some irregularities in the distribution pattern always

unit of weight) were applied with the first swath, and occur.

none with the second. At point B, 5 units were applied

with the first swath and 1 with the second for a total of

triangular pattern can make an even application if you

use half of the width of the pattern as the swath

spacing.

Figure 13. Trapezoidal deposition pattern of dry

material across a swath.

The trapezoid shown in Figure 13 is a common pattern

generated by granular spreaders. The swath spacing for

a pattern of this shape is determined by the following

equation:

(AD + BC) ÷ 2 = swath spacing

Zero granules were caught at points A and D. The

amount caught was the same for each pan between

points B and C. If the distance between A and D is 60

feet, and the distance between B and C is 30 feet, then:

(60 + 30) ÷ 2 = 45 feet

SWATH IRREGULARITIES

pattern as the swath width. Instead, you must plot each

earlier represent ideal situations. In practice, though,

After you plot the sample and determine the swath, formulation. They also won’t change appreciably from

check to see if the distribution of the granules remains ten to 20 pounds per acre. Thus, the same swath width

within acceptable tolerances (that is, where the amount can be used for this range of application rates, and an

within each collection pan is within five percent of the annual check will be sufficient, provided that the

average). equipment isn’t changed or damaged.

Non-symmetrical distribution pattern. A common

type of irregularity in the swath is non-symmetrical

distribution; that is, for any given swath, the pattern on

the right side of the aircraft is different from that on the

left.

If you fly all passes in the same direction in a race track

pattern, and there is 50 percent overlap, the left wing

pattern comes over the right wing pattern (or vice versa)

and results in a perfect total pattern. If you fly a

back-and-forth pattern, the left wing overlaps the left

wing and the resulting pattern isn’t acceptable.

The goal of calibration is to make distribution patterns as

even as possible and the same on both sides of the

aircraft. If you must adjust the pattern halfway out on

the left side, adjust the flow at the gate halfway left to

center. Or you may have to adjust the spreader vanes

halfway left from center.

Determine the actual application rate. After

checking the swath width, pattern and calibration of the

spreader, measure the application rate per acre. To do

this, load a known weight of pesticide product into the

hopper. Fly a known number of passes of known length

(minimum four passes, two in each direction), then

weigh the remaining material. The initial weight minus

that of the remaining material is the amount you applied.

You can determine the acres covered in the test run as

follows:

Number of swaths X field length (ft.) X swath width

(ft.) ÷ 43,560 sq. ft. per acre = acres covered

The application rate is:

Pounds of material applied in the test run ÷ acres

covered in the test run = pounds per acre

Once you determine the swath width and pattern, they

usually won’t change for the same plane, spreader and

Still, you should check the application rate whenever you

get a chance. Such checking shows exactly how many

pounds were applied for each job. Calculate the rate per

acre to check on the gate setting several times a day,

and keep records of your checks. Many things can

happen to affect the rate, including these:

! Foreign material may enter the hopper and plug a

gate or spreader opening.

! Moisture may condense in the hopper overnight.

The resulting sticky material would affect

application rate.

! Water may splash onto the spreader during taxi or

take-off and cause wet areas around the openings,

thus reducing the flow of granules.

By continually checking your delivery rate and

correcting any problems, you will consistently make

effective and accurate applications.

FIELD OPERATIONS

Scout the field from the air before actually starting spray

operations. Circle the field at a very low altitude, but

high enough to clear all obstructions by at least 50 feet.

Look for wires and other obstructions (trees, buildings,

windmills, radio antennas, road signs, pipeline markers

and fences) in and near the fields to be treated. Be

aware that trees may conceal power lines. Regard any

break in the cultivation pattern in the field with suspicion.

After you circle the field and note the obvious hazards,

fly just above and to one side along each power or

phone wire and check each pole. Look for branch wires,

guy wires, and transformers. Many times a wire is hard

to spot from above, but if you look at the pole tops you

can see the insulators that attach these wires to the pole.

Transformers usually have a branch wire that goes to a

house, well or other structure. If a house is near the

treatment area, look for a line coming in from

somewhere to determine by what route it gets its power.

A guy wire will normally be placed on the opposite side

of a pole from a branch wire or at the pole where a

main line makes a turn.

Always remember that conditions change. The wire you

flew under last year (or last week, for that matter) may

have a new one under it today. You may be able to get

under a wire in the spring when a crop is first planted,

but not later in the year when the crop is taller. And a

field that had no lines last week may have power or

phone lines today. Heat expands wires, making them

lower to the ground during hot summer days.

FLIGHT PATTERNS

Practice safe flying procedures during application to

protect you, your ground crew, and the environment and

to ensure that the pesticide you are applying will be

effective.

In field. Pilots normally fly back and forth across the

area being treated in straight, parallel lines (Figure 14).

However, a race-track pattern may be more energy-

efficient for some fields or more appropriate in situations

where it allows the aircraft to avoid sensitive areas.

Remember that an airplane can’t deliver a uniform spray

pattern if the flight line isn’t straight.

In mountainous terrain, where areas are too hemmed in

to permit back-and-forth flying, make all treatments

downslope. Upslope treatments are extremely

dangerous.

Mark each swath to ensure uniform coverage and to

avoid excessive overlap or stripping of the area.

Whenever possible, make the flight lines or swaths

crosswind to assist in overlap and coverage uniformity.

Begin treatments on the downwind side of the areas so

that you can make each successive swath without flying

through chemicals suspended in the air from previous

swaths (Figure 14). Also try to make the flight lines

lengthwise to the treated area to reduce the number of

turnarounds.

Figure 14. Routine turnaround flight patterns for

aerial application.

Speed. Maintain constant airspeed during aerial

application. Remember that calibration of dispersal

systems depends on flow rate (gallons or pounds per

minute) and flight speed. No device is available that

changes flow rate automatically and proportionately as

the flight speed changes. Therefore, once the dispersal

apparatus has been properly calibrated, you must keep

the speed constant during each swath to ensure uniform

coverage of the area This is another reason to apply

pesticides crosswind. By doing so, you avoid the adverse

effects of head- and tailwinds on application rate.

Altitude. Altitude is usually determined by the

formulation of material being applied. For example, liquid

pesticides must be applied from a low height (up to one-

half the wingspan) to reduce drift. Granular pesticides

are usually applied from wingspan height.

You must keep the selected height constant during each

swath run to obtain uniform coverage of the treated

area. Maintain the same height you used when you

checked the pattern of deposition and determined

effective swath width.

APPLICATION AROUND OBSTRUCTIONS

Power and telephone lines. If a wire is close to trees,

it’s safer to fly under the wire and then pull up and go

over the trees than it is to enter the field over trees and

then go under the wires. In the latter situation, you must

judge the pull out at the ground and determine then if

there is room to get under the wire. This is very

dangerous. Don’t fly under wires that have fences or swath spacing or distance the aircraft must move over,

other objects under them. maneuverability of the aircraft, power, load remaining,

Obstructions beside and at end of field. If

obstructions (trees, power and telephone lines, or

buildings) are located at the beginning or end of the

swath, turn the spray on late or shut it off early, perhaps

one or two swath-widths from the end of the field. Then

when the field is completed, fly one or two swaths

crosswise (parallel to the obstruction) to finish out the

field. Even though you may be over the target area, you

mustn’t disburse materials when dropping in or pulling

out of the field. The deposition pattern will be distorted

and the pesticide will be likely to drift.

If there are obstructions along the sides of a field, fly

parallel and as close to the obstruction as you safely

can. Leave an untreated border strip adjacent to

buildings, residences, and livestock areas to help avoid

pesticide drift. You may treat obstructed borders when

the wind is blowing toward the target area.

Obstructions within a field. Approach a tree, pole, or

other obstruction that is within a field the same way you

would if it were at the end of the field -- stop spraying

one or two swath widths from the obstruction. After

pulling up, make a 180-degree turn before dropping in on

the other side. This will allow you to control the speed

sufficiently to avoid overshooting the other side. Work

past the obstruction, then run one or two swath widths

on each side of it to complete the treatment around it.

THE TURNAROUND

The turnaround is performed more often than any other

maneuver during aerial applications. When executed

poorly, it’s a major cause of accidents. The pullup and

downwind turn puts the aircraft in a low-speed,

high-drag situation, so it must be executed carefully.

You should never look back; accomplish orientation for

the next swath before the pullup.

If possible, start the turnaround at the end of each swath

after pulling up over obstructions. When applying

pesticides in the back-and-forth pattern, start the

turnaround by turning 45 degrees downwind, leveling off

for several seconds, then making a smooth coordinated

reversal of 225 degrees (Figure 14). The number of

seconds you spend in level flight is determined by the

wind, temperature and elevation.

As you complete the turn, orient yourself to line up for

the next swath. Pilots often encounter difficulty during

this part of the turn, so pace yourself. Avoid fast or

intricate maneuvering to get into position. Complete the

turnaround before dropping in over any obstructions on

the next swath. Any turning while dispensing will distort

the distribution pattern and make even application

impossible.

Avoid snapping reversal, lowball or wingover turns.

When you must make a turn by going upwind first, you

need more space and time to complete the turn.

Avoid turnarounds over residences, farm buildings,

penned poultry or livestock, watering places, ponds and

reservoirs. Flying in a racetrack pattern may help you

avoid these sensitive areas. Always stop the discharge

before pulling up or making turnarounds.

APPLYING GRANULES

Airspeeds of 100 to 120 mph (faster for some airplanes,

slower for helicopters) are recommended when applying

granules. These speeds maintain good airflow through

the spreader and obtain proper distribution and maximum

swath width. The flying height, airspeed, and correct

ground track must be held as constant as possible to

obtain uniform results. Crosswinds have considerable

effect on offsetting the dispersal pattern from the ground

track centerline because of the flying height required.

Head or tail winds affect ground speed, and adjustments

in flow rate and/or airspeed may be required to give

uniform distribution on alternating upwind-downwind

passes. Monitor operating conditions and weather

changes carefully when you apply these materials,

because a no-wind condition is seldom encountered for

any length of time.

You can obtain maximum swath width at a certain

wheel height above the crop. This height varies with the

density, size and grading of the particles of material

being applied. For most materials, this is in the range of

40 to 60 feet wheel height. Effective wheel height is

determined by the lateral distance the spreader throws

the heavier particles. Flying below this height allows

particles to hit the ground while still traveling in the ! Be acquainted with each chemical used, knowing

spanwise direction. Flying above this height achieves no how to handle it safely, what clothing and devices

increase in swath width because particles fall vertically should be worn for protection, antidotes that are

after the lateral energy is dissipated. Don’t fly higher required in the event of accidental overexposure,

than necessary, or you may experience problems with special precautions that must be observed when

increased swath displacement and difficulty in applying chemicals, where chemicals can be used

maintaining desired ground-track height. safely, and the hazards if chemicals are applied

FERRYING

Fly at an altitude of at least 500 feet during ferry flights

between the airstrip and worksite, whether the tanks are

loaded or empty. Avoid flying over farm buildings,

scattered residential areas, and penned poultry or

livestock. Too often, because of the noise they make or

their mere presence, agricultural aircraft are accused of

damaging or contaminating property. If you must make

many trips back to the same area, avoid taking the same

route each time. Deviate one-eighth to one-fourth mile

off direct course to avoid flying close to the same areas

each time.

PROPER HANDLING AND

USE

Every pesticide comes with its own set of risks to

humans and the environment. Everyone in your

operation has a responsibility to understand and avoid

these risks. If the risks are realized, you must know how

to respond to them.

PILOTS

The pilot is responsible for efficient and successful aerial

application. Training, ability, skill, judgment and

competence can’t be overemphasized. A pilot must:

! Determine the best direction in which to spray a

block and adeptly maneuver an aircraft that is

loaded to its maximum legal weight.

! Be trained in crop recognition, not only to ensure

that the correct field is treated but, more

importantly, to ensure that any drift damage to

adjacent crops is minimal.

! Read the label, and comply with application rate and

safety precautions.

incorrectly or in the wrong places.

! Know how weather affects the application of

sprays and granules to crops.

! Master his or her aircraft, using only the maneuvers

that can be performed safely and avoiding others,

and know the maximum load limit from short, rough,

temporary airstrips.

Above all, the pilot must be aware of his or her

own limitations in the aircraft.

Pilots should use extreme caution when loading aircraft

with pesticides. It’s hard, even with normal protective

clothing and equipment, to load without some exposure.

Accumulated exposures may bring on mild pesticide

symptoms, including dizziness and fixed contraction of

the pupils (miosis) of the eye. The latter has been

reported to cause diminished visual acuity, especially at

night.

These mild symptoms may not be as serious to ground

applicators or the ground crew, but they are potentially

fatal to a pilot, especially during night applications. If

pilots are exposed when dispensing pesticides and during

loading operations, they may accumulate enough dosage

to trigger symptoms. When crosswinds occur, the pilot

should begin application on the downwind side of the

field to avoid flying through the previous swath.

There is evidence that accidental, direct eye

contamination by organophosphates may cause

contraction of the pupils for from seven to ten days

without any other symptoms. There have been several

reports of fatal injury to agricultural pilots who were

directly exposed to organophosphates. Miosis was

definitely identified following the crash.

It’s very hard to prove that “pilot error” crashes were

caused by pesticide exposure, but present evidence

suggests pesticide exposures should be kept to a gloves in an enclosed container to prevent contamination

minimum. Pilots who exhibit symptoms characteristic of of the cockpit's interior.

pesticide poisoning shouldn’t fly until the symptoms

disappear. Under the WPS, pilots may substitute certain protective

Remember, your body will tolerate small amounts of equipment. The substitutions that are allowed depend on

most pesticides. But if you accumulate doses of whether the cockpit is enclosed or open.

pesticide from various operations -- flying, loading,

mixing or cleaning, symptoms will begin when you reach

a certain level.

There have been a number of air crashes after the pilot

was drenched with pesticide from a ruptured spray tank.

Many pesticides are rapidly absorbed through the skin as

well as entering through the respiratory route. Always

remove contaminated clothing as soon as possible, then

run for the nearest water for washing -- whether that is

a ditch, creek, pond or hose. This isn’t the time for

modesty. The California Department of Health reported

one pilot who, though not critically injured in the crash,

was splashed with TEPP and phosdrin. He died of

organophosphate poisoning 20 minutes later.

Use a filter- or canister-type respirator appropriate for

the chemical being applied. If you need one for extended

periods during hot weather, use a respirator and

crash-helmet combination that is ventilated with fresh

air.

PROTECTIVE CLOTHING AND

EQUIPMENT

The unit in Applying Pesticides Correctly provides an

excellent discussion of the types of, and need for,

protective clothing and equipment. The Worker

Protection Standard (WPS) requires pesticide

manufacturers to list minimum personal protective

equipment and clothing requirements on the label. The

label must specify the type of gloves to wear (such as

nitrile) and, if applicable, the type of respirator to use

and the respirator's MSHA/NIOSH approval-number

prefix. (For example, the label might say to use an

organic-vapor-removing cartridge and pre-filter with

MSHA/NIOSH approval number prefix TC-23C.)

The WPS requires you to wear the protective gloves

required by the labeling when entering or exiting an

aircraft whose exterior is contaminated by pesticide

residue. Once inside the cockpit, you must keep the

gear for label-specified personal protective clothing and

Enclosed cockpits. Persons in enclosed cockpits are

not required to wear personal protective clothing or

equipment, but they must wear long-sleeved shirts, long

pants, shoes and socks.

Open cockpits. Persons in open cockpits must wear

the personal protective clothing and equipment required

for a ground applicator using that product, except that

chemical-resistant footwear isn’t required. You may

substitute a helmet for chemical-resistant headgear and

a visor for protective eyewear.

GROUND OR LOADING CREW

Most pesticides are toxic in varying degrees. The

loading or ground crew has the most direct contact with

pesticides and must wear protective clothing and

equipment. The label on the pesticide specifies the

protection needed.

When you work around chemicals:

! Don’t breathe fumes from the mixer when you pour

concentrated chemicals into mixing equipment.

Wear your respirator and face shield as required.

! Don’t eat your lunch or smoke around mixing

equipment. Move out of the loading area, then wash

your hands thoroughly.

! Don’t carry cigarettes or anything you eat in your

pocket while you load dust or liquid; they absorb

chemical fumes.

! Chemicals can poison you by absorption through the

skin, eyes or mouth or by breathing fumes. Protect

yourself at all times.

! Triple-rinse or pressure-rinse chemical containers

immediately after emptying them.

! Never leave emptied chemical containers on an Point the airplane toward the runway while it’s being

unattended runway. Bring all containers back to loaded to avoid making sharp turns with a fully loaded

where you normally dispose of them. Keep them airplane. Locate mixing tanks so that prop blast doesn’t

under lock and key, full or empty. blow sand or debris toward them. A wide, circular

! Stand upwind of mixing equipment when you pour area in the middle is often used. The fuel may also be in

chemicals or while you wait for the airplane to the middle of the circle so you can refuel while loading;

return for another load. however, remember to keep fuel and pesticides well

Wear protective clothing when you handle

chemicals:

! Never handle insecticides without good, clean,

unlined rubber gloves.

! Wear enough protective clothing to keep as much of

the body unexposed to the chemical as possible.

Liquid Category I and II chemicals require that you

also wear a waterproof apron when you mix and

load.

! Don’t wipe your hands on your clothes; this will

contaminate them. Take a clean change of overalls

to the job with you.

! Don’t wear dirty or contaminated clothes on the job

or home. Wash your clothing regularly.

! Wear good rubber footwear to avoid contamination

with chemicals that are on the ground in the loading

area.

! Dispose of emptied pesticide containers properly.

! Wash thoroughly with soap and water immediately

if you accidentally spill chemicals on yourself.

Believe what you read on all labels. If you don’t

comply with them, you place yourself and others at

grave risk.

AIRSTRIP OPERATION

A well-organized airstrip ensures that the aircraft spends

the minimum amount of time on the ground and the

maximum time spraying. Airstrip layouts vary, but fuels

and pesticides must be kept well apart and protected

from sunlight and environmental extremes.

turnaround area with the chemical storage and mixing

apart.

Load the aircraft via a closed-transfer system. Do all

ground work on an impervious surface that allows any

accidental spills to be contained, properly recovered, and

used or disposed of.

You may need to reduce the aircraft payload from the

manufacturer's maximum specification to compensate

for airstrip conditions or for the effect of atmospheric

conditions.

AERIAL-APPLICATION CHECKLISTS

We suggest that pilots and crew, including flaggers,

review a checklist at least weekly to help them avoid

becoming complacent and careless.

Pilot checklist. The pilot should do the following

before, during and after any application:

1. Don’t load or handle highly toxic pesticides,

especially hazardous formulations, during any

operation.

2. Turn off the engines during loading operations.

3. Wear an approved safety helmet, long-sleeved shirt,

long pants, shoes, socks, and other protective

equipment specified on the pesticide label.

4. Check the field and surrounding area before you

apply chemicals to be sure there are no animals,

humans, crops, waterways, streams or ponds that

might be injured or contaminated either by direct

application or drift.

5. Don’t fly through the suspended spray of an

application.

6. Stop treatment if winds rise and create a drift

hazard.

7. Don’t turn on dispersal equipment or check the flow

rate except in the area to be treated.

8. Refuse to fly if the customer is the flagger. Also,

refuse if the customer insists on having pesticide

applied in a manner and at a time that may create a

hazard to crops, humans, animals, and the

surrounding environment.

9. Read the label, and know the hazardous

characteristics of the pesticides.

10. Know how far and in what direction the chemical

will drift (that is, use smoker).

11. Don’t spray over the flagger or anyone else.

12. After you complete a job, don’t dump remnants on

the field. Carry it to the loading area so the crew

can store it in a safe manner for reuse as make-up

water.

Ground crew checklist. The ground crew should do

the following before, during and after any application.

Also, the ground crew should be familiar with the pilot's

checklist.

1. Clean aircraft often, especially the cockpit.

2. Tightly seal tanks and hoppers so the chemicals

won’t blow back over the pilot.

3. Cover the hopper as soon as loading is completed.

4. Remove any chemical spilled near the fill opening.

5. When handling pesticides or cleaning aircraft or

other equipment, use extreme care, and wear

protective clothing.

6. Don’t stand in runoff water or allow it to splash on

you.

7. Change clothing after handling pesticides or washing

the aircraft and contaminated equipment.

CLEANING EQUIPMENT

Clean application equipment adequately, so that it

operates properly. This helps prevent cross-

contamination, which may result in plant damage or

illegal residues. Generally speaking, it’s easier to remove

fungicides and insecticides than herbicides. Therefore,

when possible, schedule daily operations so fungicides

are applied first, followed by insecticides. Apply

herbicides last, so they can be thoroughly washed out at

the end of the day.

Pesticides vary considerably, so adapt rinse procedures.

You can usually remove water-soluble powders and

emulsifiable concentrates with water. However, you

may have to rinse certain oil formulations of 2,4-D with

kerosene or another solvent before you wash them with

water and detergent or other additives, such as charcoal.

Follow the manufacturer's recommendations on the

product label to develop acceptable washing procedures

for specific pesticides. Wash tanks and hoppers

adequately inside and out to prevent carryover of

pesticides and damage to sensitive crops.

Provide a specific area in which to flush and clean

equipment. Locate it away from the office and tiedown

area so the equipment maintenance area will be

protected from contamination. A pad of concrete or

other impervious material three feet to five feet wider

than the wingspan of the aircraft is ideal. Slope it to a

central collection sump that’s equipped with a pump to

transfer waste to a suitable storage tank. Cover the pad

to prevent the collection of rain.

Follow these procedures for equipment on the collection

pad:

Emulsifiable concentrates and wettable or soluble

powders

1. Drain excess spray solution from the tank or

hopper.

2. Add a small amount of water and detergent to tank,

then circulate and discharge it completely.

3. Add clean water to the tank, circulate it, and

discharge it completely again.

4. Check nozzles and screens and, if necessary, 4. Agitate it thoroughly for at least five minutes, pump

disassemble them, clean them thoroughly, and the solution through the hoses, and dispose of liquids

reassemble them. in an appropriate manner.

5. Clean the outside of equipment, and collect and 5. Rinse the system thoroughly with clean water, and

properly dispose of the wash water. dispose of liquids in an appropriate manner.

Phenoxy herbicide. Herbicides, especially ester Important: These procedures don’t take

formulations of 2,4-D and related products, are hard to

remove. Even in tiny amounts, they pose serious

problems of phytotoxicity to sensitive crops.

Amine formulations (water-soluble)

1. Drain excess spray from the tank.

2. Flush the system with a small amount of

water-detergent mixture, and collect the waste.

3. Fill the tank with a solution containing one quart of

household ammonia per 25 gallons of water. Agitate

it and pump enough out to fill the hoses and boom.

Let this stand for 12 to 24 hours.

4. Check the nozzles and screens, disassemble them if

it’s necessary, clean them, and rinse them

thoroughly.

5. Drain the ammonia solution and rinse it thoroughly

with clean water. Dispose of contaminated liquids in

an appropriate manner.

6. Clean the outside of equipment. Dispose of

contaminated liquid in an appropriate manner.

Ester formulations (oil-soluble)

1. Drain any excess spray from the tank.

2. Rinse the tank with kerosene instead of water, flush

it, and dispose of liquids in an appropriate manner.

3. Fill the system with water containing two ounces of

laundry detergent and four ounces of activated

charcoal for each ten gallons of water.

precedence over any specific instructions that may

appear on a pesticide product label. Label

instructions must always be followed explicitly.

Even these cleaning procedures don’t guarantee that all

traces of pesticide have been removed. Therefore,

before treating a sensitive crop with equipment

previously used to apply herbicides, you may want to fill

the equipment with water and apply it to a small crop

area to determine the phytotoxic potential.

PESTICIDE CONTAINERS AND DISPOSAL

It’s against the law to open-dump pesticide containers,

whether they are rinsed or not. Pouring rinse water,

unused mixtures, or unused concentrates onto the

ground or water is illegal. These generate hazardous

waste.

Container disposal. In order for pesticide containers

to be classified as solid waste rather than hazardous

waste, the pesticide containers must be properly rinsed.

Once the container is classified as a solid-waste product,

it can be legally disposed at a sanitary landfill.

Liquid pesticide containers must be rinsed immediately

after they have been emptied. After the container is

cleaned, puncture and/or crush it. Applicators have two

options available to clean containers, pressure-rinse or

triple-rinse.

Pressure-rinse. A pressure-rinse nozzle screws onto

a hose as does a garden nozzle, but it’s much heavier,

has a sharp point for puncturing the container, and

sprays water in several directions to ensure good rinsing.

To pressure-rinse, allow the container to drain into the

spray tank for 30 seconds. While holding the container

over the tank opening, insert the probe of a pressure-

rinse nozzle into the bottom of the container.

For plastic containers, insert the probe near the corner labeled site or crop. Otherwise, collect the spray

or edge of the bottom. For metal containers, especially mixture, and hold it in rinsate tanks.

larger than five gallon sizes, make the initial hole through

the bottom with a punch or chisel, then insert the probe

through the hole.

Turn the rinse unit on to rinse the container. Rotate the

nozzle slowly, allowing water to reach all sides of the

container. Continue to flush for a sufficient time (20 to

30 seconds) to adequately rinse the container.

Turn the water off. Drain all rinsed contents from the

container into the spray tank. Remove the nozzle from

the container. The container has been sufficiently

cleaned.

Triple-rinse method. Drain the container into the

spray tank for 30 to 60 seconds. Fill the container one-

fourth to one-fifth full of water. Replace the cap and

vigorously shake it for 30 seconds. Remove the cap, and

drain the contents into a spray tank for 30 seconds.

Repeat this rinsing two more times. Puncture and/or

crush the container to ensure it won’t be used again.

Bag disposal. Empty the content of the pesticide bag

into the applicator tank or hopper until all the pesticide

has been removed.

Tear open the container to make sure it’s completely

empty. Wrap the container in paper, and place it in a

solid-waste collection system, or carry it to a sanitary

landfill.

Disposing of unused mixtures. Try not to mix more

than is needed. If some spray mixture is left, spray it on

a labeled crop or site. You can spray rinsate over a

labeled crop or site, or transfer it into a rinsate holding

tank. If you store rinsate, you must have proper

hazardous-waste storage permits. Label the tank by

chemical type. Use it as make-up water for later tank

mixtures of the same product formulation. Only 20

percent of rinsate can be used for make-up water; the

rest must be clean water.

Cleaning out sprayer tanks, lines and nozzles. If it

isn’t desirable to spray unused mixtures over a labeled

crop or site, dilute four to 12 gallons of mixture with 40

to 70 gallons of clean water, and spray it over the

Warning: It’s possible that local landfills may have

further restrictions on pesticide-container disposal.

Locally owned or run landfills have the right of refusal.

FLAGGERS

Use permanent or electronic markers to eliminate the

possibility of harm to flaggers. However, if flaggers

must be used, no person other than flaggers should be in

the field to be treated. Your flaggers should:

! Know which chemical is being applied so they can

wear appropriate protective clothing and equipment

and so they react properly in case of emergency.

Flaggers must wear chemical-resistant headgear if

the application may result in overhead exposure.

! Always start flagging on the downwind side and flag

into the wind, never with the drift. Once the aircraft

has achieved a satisfactory heading on its swath

run, the flagger should move to the next swath in

order to maintain a safe separation from the

aircraft. The pilot can maintain additional separation

by working a swath behind the flagger.

! Avoid flagging near power lines or fences. If you

cut the wires or snag the fence, the trailing wires

could hurt a flagger. Flaggers should never direct

you toward a guy wire.

! Watch the aircraft at all times, and never turn their

backs on an approaching aircraft.

! Move over to the next position after the aircraft is

lined up for a pass.

! Stay at the job site until the application is completed

so they can help in case of an emergency.

! Advise you of any hazard or problem he or she

sees.

Flaggers are considered pesticide handlers under the

Worker Protection Standard. Thus, you or their

employer must provide them with the personal protective

clothing and equipment, safety training, decontamination being used and what, if any, medical treatment to

site, and other provisions as required by the WPS. provide.

IF AN AIRCRAFT CRASHES

Train the ground crew and flaggers in the proper

procedures to use in the event of a crash. Share the

following information with them, and develop a crash

response plan. The ground crew and flaggers must

remember the following:

! Don’t panic. Stay calm, and try to help the pilot as

much as possible.

! If a radio is available, call for additional help.

! Have a fire extinguisher available at all times. Take

it to the aircraft immediately.

! If the aircraft is on fire, stay out of the smoke. Get

the pilot out, and moved him or her to a safe

distance. If it isn’t too dangerous, try to extinguish

the fire.

! See if the pilot is injured. If so, serious injuries

demand immediate attention. Don’t move a pilot

who is seriously injured or unconscious unless the

aircraft is burning. Check for strangling, choking or

bleeding. If an artery is cut in an arm or leg, use

direct pressure on a pressure point. Use a tourniquet

only as a last resort. Call an ambulance and rescue

squad. Give your precise location. Then call your

company to apprise them of the situation.

Accompany the pilot to the hospital.

! If the pilot isn’t seriously injured but has been

exposed to the pesticide, help him or her to the

decontamination site or the nearest water source.

Wash several times -- with soap, if possible. In a

number of air crashes, the pilot has been drenched

with pesticide from a ruptured spray tank. This

exposure may cause more harm than the physical

injuries suffered in the crash, so you must act

quickly. Take the pilot to a doctor or hospital,

whether or not there was any exposure to

pesticides. If it’s more appropriate, call a rescue

squad. Accompany the pilot to the doctor, taking a

copy of the label or material safety-data sheet with

you. This will tell the doctor what pesticide was

DRIFT

Drift is the air-borne movement of pesticide to areas

outside the target area. Reducing drift is a significant

aspect of pesticide application. Pilots who ignore the

reality of drift do so at their own risk and to the

detriment of the entire aerial application industry.

We discuss drift in detail in a unit in your Applying

Pesticides Correctly manual.

Because this is such an important topic for aerial

applicators, we’ll review some basic facts about drift

and present additional information specific to the

problem of drift in aerial applications.

FACTORS THAT CAUSE DRIFT

We can separate the factors that cause drift into two

main categories: weather-related (wind velocity,

temperature inversions, air stability, and relative

humidity) and application-related (nozzle spray,

placement of nozzles on boom, nozzle orientation,

airspeed, spray heights, operating pressures, and choice

of formulation).

WEATHER-RELATED FACTORS

Weather conditions at the time of application greatly

affect whether, and to what extent, drift will occur.

While you have no control over these conditions, you

can choose not to spray when conditions favor drift. To

make the proper decision, you must understand what

conditions affect drift and how they do so.

Wind velocity. Obviously, the distance that spray

droplets travel, and the chances that they will leave the

target area, increase with wind velocity. A simple

anemometer (an instrument that measures wind speed)

should be part of your ground equipment. Use the

anemometer as a safety measure, and keep a record of

wind speed as a legal reference.

Normally, the aircraft flies with a side wind of two to ten

mph and works upwind across the field. Under such

conditions, some larger spray droplets (>100F in

diameter) may settle on the target area more than 150 Don’t make an aerial application when a temperature

feet downwind of the flight path. You can plan for this inversion exists. To detect an inversion, measure the air

swath displacement and apply the pesticide accordingly. temperature near the ground and at some higher altitude

However, droplets smaller than 100F may settle much present if the temperature near the ground is less than

further away, perhaps well beyond the target area. This the temperature at the higher altitude. Because

drift is unacceptable. Thus, even though swath inversions tend to be localized, be sure to check

displacement occurs whenever there is even the conditions at the job site.

slightest wind, the actual drift is greater than that which

you see. Smoke is more practical to detect inversions. Inject oil

Apply pesticides when wind speed is low to minimize altitude to release a cloud of smoke. An inversion is

this risk. (However, as we’ll discuss later, you should present if the smoke levels off and travels laterally

also avoid applying pesticides when the air is almost instead of rising. It’s your responsibility to be aware of

calm.) Even when the wind is low, don’t apply pesticides an inversion by using a suitable detection technique.

if it’s blowing toward residences, livestock areas, or

other sensitive places.

Temperature inversions. Under normal conditions, importance of lateral air movement, but often overlook

temperature decreases with increasing altitude. A vertical air movement.

temperature inversion exists when temperature

increases with altitude to some point before it becomes As the ground warms up throughout the day, the

cooler. temperature at the ground surface is significantly higher

Temperature inversions are usually caused by rapid set up convection and thermal air currents that lift small

cooling of the soil surface, coupled with evaporative particles. As the air becomes more severely unstable,

cooling of crops. The lost heat radiates upward, causing vertical air currents become stronger and the size of

the air above the ground surface to be warmer than air particles that are drift-prone increases.

at or near the surface. The cooler air, since it’s heavier

than the warmer air, remains as a layer near the ground. Because these particles can be carried long distances

Maximum inversions occur when cool night under these conditions. This, along with generally higher

temperatures follow high day temperatures. The wind velocities, is part of the reason that pesticides are

inversion reaches its peak in the early morning. It then not

disappears as the sun warms the land. This causes usually applied in the middle of the day.

the air to warm at the soil

surface and re-establishes the normal temperature Generally speaking, conditions are best for spray

gradient. deposition when the air is mildly unstable and there is a

Temperature inversions provide the greatest opportunity because it prevents the buildup of harmful

for drift. During a temperature inversion, the air is highly concentrations of drift-prone particles.

stable. Small spray droplets can become trapped in the

cool air beneath the inversion ceiling. They can move It’s undesirable to spray in perfectly calm conditions,

laterally far enough and in sufficient amounts to cause because there’s no positive displacement of the

damage outside the target area. It’s unfortunate that drift-prone particle cloud. Without positive movement, an

inversions are most likely to occur in the early morning, aircraft can’t avoid flying through the cloud. It’s also not

a time when wind speeds are usually low and thus more possible to know where the drift cloud will go when air

conducive to spraying. movement begins.

(at three and 32 feet above the ground). An inversion is

onto the hot exhaust manifold while flying at a low

Air stability. Air movement largely determines the

distribution of spray droplets. We recognize the

than that above the ground. The warm air rises and may

before they settle out, you should also avoid spraying

mild but steady wind. Mildly unstable air is desirable

Relative humidity. Relative humidity (RH) affects the

rate of evaporation of water from liquid drops. The

lower the RH, the faster the loss of water and the

smaller the drop becomes. The smaller the drop, the

slower it falls and the farther it drifts. In addition, rate of

evaporation increases with decreasing droplet size; thus,

the effect of low RH is most significant when there is a

large proportion of small droplets in the spray.

While RH isn’t one of the most important factors

contributing to drift problems, its importance becomes

greater as the size of the droplet spectrum decreases.

RH doesn’t affect the rate of loss of petroleum- or

oil-based liquids. (The evaporation of these liquids varies

with temperature and each liquid's vapor pressure.)

You can’t control the RH, but you can avoid spraying

when it’s very low. Also, you can select and operate

spray equipment so as to produce few small droplets,

and you can use low-volatile solvents and carriers. We

will discuss these topics in more detail later.

Application-related factors. In many cases, smaller

droplets provide better coverage and are more effective

than larger spray droplets. However, the smaller the

droplet, the more likely it is to drift.

This is because smaller droplets take longer to settle out

and are subject to the effects of wind for a longer period

of time.

Droplets that are of most concern are those that are less

than 100F (1/254 of an inch) in diameter. These

droplets are hardly visible and remain airborne for a

significant amount of time. Thus, your goal should be to

produce the coarsest spray that will provide an effective

treatment and to minimize the total volume of these

smaller droplets in particular. Essentially, each

application-related factor we’ll discuss involves reducing

the proportion of small droplets in the spray spectrum

(Figure 15).

One way to describe the coarseness of a spectrum of

spray droplets is to use the volume median diameter

(VMD). This is the diameter for which half of the total

spray volume is of droplets larger than the VMD and

half is of droplets smaller than the VMD. Generally

speaking, the larger the VMD, the smaller the proportion

of the small, drift-prone droplets in the droplet spectrum

(Table 2).

Table 2. Basic Droplet Guide

Droplet Size

Application Based on Volume

Median Diameter, VMD (FF)

Fungicide 150-250

Insecticide 150-300

Contact herbicide 250-400

Phenoxy and incorporated herbicide 400+

Nozzle spray. Droplet size generally increases and the

percentage of small droplets decreases as the size of the

nozzle opening increases. For example, with an

operating pressure of 50 psi, changing from a D4-45 to

a D6-46 nozzle will increase the VMD from about 150

to about 280.

Placement of nozzles on boom. Nozzles must be

properly distributed along a boom to account for prop-

wash displacement and wing-tip vortices. Correct

distribution is important to ensure a uniform dispersal

pattern and to prevent drift that may result if too much

spray is caught up in the vortices. This topic, including

the implications on drift, was covered in the unit

“Calibration.”

Nozzle orientation. Orientation of nozzles relative to

the direction of flight affects the droplet sizes produced

by the nozzles (Figure 15). This is attributed to the

difference in the relative velocity between the air

and spray liquid

resulting from various nozzle orientations.

When the nozzle is pointed back (in the same direction

as the airflow), the air shear forces that break up the

spray are less than at any other orientation. The droplet

spectrum produced will be relatively large. A nozzle

pointed down will produce a smaller droplet spectrum

because of the higher shear forces.

Figure 15. Droplet size is greatly affected by nozzle Because the small droplets add up to 50 percent of the

orientation. More or less shear and liquid break-up total volume, the VMD is somewhere between the size

may be obtained by varying orientation of nozzles of the large and the small droplets.

with direction of flight.

The maximum shear forces and smallest droplets would degrees down, and now the spray consists of seven

be generated if the nozzle was oriented forward into the droplets: one large droplet, the same size as before and

airstream. This is normally not done except in situations still containing 50 percent of the spray volume; one

where extremely fine droplets are desired (for example, smaller droplet, containing 25 percent of the spray

applications in forested areas). Also, doing so tends to volume and the same size as before; and five even

bathe the aircraft in chemical spray. To give you an idea smaller droplets, each containing five percent of the

of how important nozzle orientation is in reducing drift, spray volume (the five adding up to 25 percent of the

let's look at some data. spray volume). The VMD has not changed, but in the

Spray droplets less than 100F in diameter are the more prone to drift.

droplets that are most likely to drift and thus cause

damage outside the target area. When a D6-46 nozzle is This is an oversimplified example, but it illustrates the

oriented straight back under specific conditions to obtain point that the size distribution of droplets can change

the data, the VMD of the droplet spectrum is 450F, and markedly, even if the VMD changes only slightly or not

droplets less than 100F account for 0.2 percent of the at all.

total spray volume. If the nozzle is oriented straight

down under the same conditions, the VMD becomes

290F, and droplets less than 100F now account for 2

percent of the total spray volume. This is a ten-fold

increase in the volume of spray that has the potential to

cause damage outside of the treatment area. Obviously,

orienting the nozzles straight back is a simple and

effective way to greatly reduce drift.

While it helps to know the VMD, it’s important to know

the total spectrum produced by an atomizer. For

example, a D8-46 nozzle, used under specific conditions

to obtain the data, produces the same VMD (355F),

whether directed straight back or back and down 45

degrees. While that means that at each position, one-half

of the total spray volume is in droplets less than 355F, it

doesn’t mean that the size distribution of those droplets

is the same. In fact, a greater proportion of the droplets

are less than 100F when the nozzle is oriented back and

down 45 degrees. In this case, the result is a four-fold

increase (from 0.3 percent to 1.2 percent) in the volume

of droplets that are less than 100F.

To further explain the last example, suppose only three

droplets were produced when the nozzle was directed

straight back: one large droplet, containing 50 percent of

the total spray volume, and two equal-sized smaller ones,

each containing 25 percent of the total spray volume.

Now suppose you change the nozzles to back and 45

latter case there are even smaller droplets, which will be

Airspeed. Droplet size decreases as airspeed increases

because of the greater wind shear forces acting on the

droplets emitted by the atomizer.

Spray height. It’s a common misconception that

increasing the aircraft spray height will result in a wider

swath. Actually, swath width will increase only up to a

height of about 15 feet. However, the crosswind effect

increases the displacement of the swath as height is

increased. Not only must droplets fall farther and thus

be exposed to the crosswind longer, but wind velocity

tends to increase with height above the crop.

In general, you should use the lowest spraying height

consistent with aircraft safety and effective coverage.

Operating pressure. Increasing operating pressure

usually reduces droplet size and increases the potential

for drift. Thus, you should use the lowest pressure

necessary to get the job done properly. However, by

using a solid cone nozzle pointed straight back,

increasing pressure increases droplet size because it

decreases the wind shear on the droplet.

If you need to increase your spray volume significantly,

you should use nozzles with larger openings or use more

nozzles on the boom, because an increase in pressure

doesn’t result in a proportional increase in output; you

must increase pressure fourfold to increase output

twofold.

Formulation. While granules drift less than liquid

sprays, they aren’t available for many of the applications

you make. However, even when you must use a liquid,

you can reduce the likelihood of drift by selecting an

appropriate formulation or product. Use low-volatile

sprays to prevent vaporization; oil-based sprays also

reduce the rate of vaporization. (Remember,

vaporization increases with increasing temperature

and/or decreasing RH.) Vaporized spray will move with

air currents and may cause damage outside the target

area.

You can also use adjuvants, which act as thickening

agents and increase the proportion of large droplets in

the spray spectrum. The benefits of using an adjuvant

will be largely negated if you don’t orient the nozzles

back (at worst, back and 45 degrees down) or if you use

inappropriate nozzles or excessive operating pressure.

Always check the product label before adding any

adjuvants to the spray tank.

THREATENED AND WORKER PROTECTION

ENDANGERED SPECIES STANDARDS

The Endangered Species Act (ESA) was passed by

Congress to protect certain plants and wildlife that are

in danger of becoming extinct. This act requires EPA to

ensure that these species are protected from pesticides.

Formulation of the Utah Threatened and Endangered

Species/Pesticides Plan is a cooperative effort between

federal, state, and private agencies and producers/user

groups, and is a basis for continuing future efforts to

protect threatened and endangered species from

pesticides whenever possible. Furthermore, this plan

provides agencies direction for management policies,

regulations, enforcement and implementation of

threatened and endangered species/pesticide strategies.

EPA has therefore launched a major new initiative

known as the Endangered Species Labeling Project. The

aim is to remove or reduce the threat to threatened and

endangered species from pesticide poisoning. EPA has

the responsibility to protect wildlife and the environment

against hazards posed by pesticides. The ESA is

administered by the U.S. Fish and Wildlife Service

(FWS) in the U.S. Department of Interior. The Fish and

Wildlife Service will determine jeopardy to threatened

and endangered species and report to EPA. EPA and

FWS will work cooperatively to ensure that there is

consistency in their responses to pesticide users and to

provide necessary information. The Utah Department of

Agriculture is acting under the direction and authority of

EPA to carry out the ESA as it relates to the use of

pesticides in Utah.

Maps will show the boundaries of all threatened and

endangered species habitats in affected counties. The

maps identify exactly where, in listed counties, use of

active ingredients in certain pesticides is limited or

prohibited. Product labels will be updated as necessary.

The updated labels will reflect any additions or deletions

to the project. Because EPA's approach to the

protection of threatened and endangered species was in

the proposal phase at the time this guide was published,

any and all of the above information on threatened and

endangered species is subject to change and may not be

valid.

This final rule, which was proposed in 1988 and that

substantially revised standards first established in 1974,

affects 3.9 million people whose jobs involve exposure

to agricultural pesticides used on plants; people

employed on the nation’s farms; and in forests, nurseries

and greenhouses. The standard reduces pesticide risks

to agricultural workers and pesticide handlers. The

standard is enforceable on all pesticides with the Worker

Protection Standard labeling. The provisions became

fully enforceable in January 1995.

Agricultural workers in Utah now have a far greater

opportunity to protect themselves, their families and

others. These workers will know, often for the first time,

when they are working in the presence of toxic

pesticides, understand the nature of the risks these

chemicals present, and get basic safety instructions.

Among the provisions of the rule are requirements that

employers provide handlers and workers with ample

water, soap and towels for washing and decontamination

and that emergency transportation be made available in

the event of a pesticide poisoning or injury. The rule also

establishes restricted-entry intervals -- specific time

periods when worker entry is restricted following

pesticide application -- and requires personal protection

equipment (PPE) for all pesticides used on farms or in

forests, greenhouses and nurseries. Some pesticide

products already carry restricted re-entry intervals and

personal protection equipment requirements; this rule

raised the level of protection and requirements for all

products.

Other major provisions require that employers inform

workers and handlers about pesticide hazards through

safety training, which handlers have easy access to

pesticide-label safety information, and that a listing of

pesticide treatments is centrally located at the

agricultural facility. Finally, handlers are prohibited from

applying a pesticide in a way that could expose workers

or other people.

GROUNDWATER

CONTAMINATION BY

PESTICIDES

Utah has implemented a comprehensive and coordinated

approach to protect groundwater from pesticide

contamination.

Formulation of the Groundwater/Pesticide State

Management Plan is a cooperative effort between

federal, state, and private agencies and producers/user

groups; it provides a basis for continuing future efforts

to protect groundwater from contamination whenever

possible. Furthermore, this plan provides agencies with

direction for management policies, regulations,

enforcement and implementation of groundwater

strategies.

While it’s recognized that the responsible and wise use

of pesticides can have a positive economic impact, yield

a higher quality of crops, enhance outdoor activities, and

give relief from annoying pests, the Utah Department of

Agriculture is authorized by the U.S. Environmental

Protection Agency (EPA) to enforce the protection of

groundwater from pesticides. Product labels will be

updated as necessary.

The Utah Department of Agriculture, in concert with

cooperating agencies and entities, admonishes strict

compliance with all pesticide labels, handling procedures

and usage to protect groundwater in the state.

Groundwater can be affected by what we do to our

land. Prevention of groundwater contamination is

important, because once the water is polluted, it’s very

hard and costly to clean up. In some instances, it’s

impossible, especially if it’s deep underground. City and

urban areas especially contribute to pollution because

water runoff that contains pesticides runs into drainage

tunnels, then into a river or an underground stream that

drains into the river. For more complete information

about what groundwater is and where it comes from,

read the study manual "Applying Pesticides Correctly."

Shallow aquifers or water tables are more susceptible to

contamination than deeper aquifers. Sandy soils allow

more pollution than clay or organic soils, because clays

and organic matter absorb many of the contaminants.

The Federal Insecticide, Fungicide and Rodenticide Act

(FIFRA), as amended, establishes a policy for

determining the acceptability of a pesticide use or the

continuation of that use, according to a risk/benefit

assessment. As long as benefits outweigh adverse

effects, a pesticide can be registered by the EPA.

Although the intent of a pesticide application is to apply

the pesticide to the target or pest, part of the pesticide

will fall on the area around the target or pest. Rain or

irrigation water then can pick up the part that isn’t

degraded or broken down and carry it to the

groundwater via leaching.

The major factors that influence the amount of

contamination that can get into water are the chemicals'

persistence in soil, retention time or time it remains in the

soil, the soil type, the time and frequency of the

application(s), soil moisture, placement of the pesticide,

and the ability of the chemical to persist once in the

aquatic environment. Each of these factors will

influence the amount of pesticide that can leave the root

zone or soil surface and percolate to groundwater.

Although some pesticides may have a high absorption

quality, when they are applied to sandy soil, they will still

migrate to the water table because there are no fine clay

particles or organic matter to hold them. The

management and use of pesticides is up to the individual

applicator and/or land owner as to whether safe

practices are used. Water is one of our most valuable

resources; we must keep it as pure as possible.

APPENDIX I

CALIBRATION FORMULAS

This appendix contains material that supplements the

information found in the manual. This information isn’t

covered on your certification exam.

1. acres/swath run = [field length (ft.) X swath width

(ft.)] ÷ 43,560

acres/swath run = [mph X swath width (ft.) X

seconds traveled X 1.467] ÷ 43,560

2. acres/minute = mph X swath width (ft.) X 0.00202

3. gallons/acre = [gpm X 495] ÷ [mph X swath width

(ft.)]

4. gallons/minute = [gpa X mph X swath width (ft.)] ÷

495

5. gpm/nozzle = [gpa X mph X swath width (ft.)] ÷ [#

of nozzles X 495]

6. length of swath run = mph X seconds traveled X

1.466

7. minutes/acre = 495 ÷ [mph X swath width (ft.)]

8. mph = [gpm X 495] ÷ [gpa X swath width (ft.)]

mph = [0.682 X distance traveled (ft.)] ÷ seconds

9. swath runs/load = acre load in hopper ÷ acres/swath

run

swath runs/load = number of gallons in hopper ÷

[gpa X acres/swath run]

10. time (minutes)/load = [495 X number of gallons per

load] ÷ [gpa X swath width (ft.) X mph]

11. time (minutes)/swath = [60 X length of run (ft.)] ÷

[mph X 5280]

time (minutes)/swath = [length of run (ft.) X

0.01136] ÷ mph

12. time (seconds)/swath = [60 X 60 X length of run

(ft.)] ÷ [mph X 5280]

time (seconds)/swath = [length of run (ft.) X

0.68182] ÷ mph

CALIBRATION INFORMATION

Conversion:

Units

One acre = 43,560 square feet Example: ½ acre = 21,780 square feet

One mile = 5,280 feet Example: ¼ mile = 1320 feet

One gallon = 128 fluid ounces Example: ½ gallon = 64 fluid ounces

One quart = 2 pints = 4 cups = 32 fluid ounces Example: 2 quarts = 64 fluid ounces

One pint = 2 cups = 16 fluid ounces Example: ½ pint = 1 cup = 8 fluid ounces

One tablespoon = 3 teaspoons = 0.5 fluid ounces Example: 2 tablespoons = 1 fluid ounce

One pound = 16 ounces Example: ¼ pound = 4 ounces

One gallon = 231 cubic inches Example: 2 gallons = 462 cubic inches

Weight

1 ounce = 28.35 grams

16 ounces = 1 pound = 453.59 grams

1 gallon water = 8.34 pounds = 3.785 liters = 3.78 kilograms

Liquid Measure

1 fluid ounce = 2 tablespoons = 29.573 milliliters

16 fluid ounces = 1 pint = 0.473 liters

2 pints = 1 quart = 0.946 liters

8 pints = 4 quarts = 1 gallon = 3.785 liters

Length

1 foot = 30.48 centimeters

3 feet = 1 yard = 0.9144 meters

16 1/2 feet = 1 rod = 5.029 meters

5280 feet = 320 rods = 1 mile = 1.6 kilometers

Area

1 square foot = 929.03 square centimeters

9 square feet = 1 square yard = 0.836 square meters

43560 square feet = 160 square rods = 1 acre = 0.405 hectares

Speed

1.466 feet per second = 88 feet per minute = 1 mph = 1.6 kilometers per hour (kph)

Volume

27 cubic feet = 1 cubic yard = 0.765 cubic meters

1 cubic foot = 7.5 gallons = 28.317 cubic decimeters

Area and Volume Calculations:

Area of Rectangular or Square Shapes

The area of a rectangle is found by multiplying the length (L) times the width (W).

(Length) x (Width) = Area

Example: (100 feet) x (40 feet) = 4000 square feet

Area of Circles

The area of a circle is the radius (radius = one-half the diameter), times the radius, times 3.14.

(radius) x (radius) x (3.14) = Area

Example: (25 feet) x (25 feet) x (3.14) = 1962.5 square feet

Area of Triangular Shapes

To find the area of a triangle, multiply ½ times the width of the triangle’s base, times the height

of the triangle.

(½) x (base width) x (height) = Area

Example: (½) x (15 feet) x (10 feet) = 75 square feet

Area of Irregular Shapes

Irregularly shaped sites can often be reduced to a combination of rectangles, circles, and

triangles. Calculate the area of each shape and add the values together to obtain the total area.

Example: Calculate the area of the rectangle, triangle,

square, and one-half of a circle.

Another method is to convert the site into a circle. From a center point, measure the distance to

the edge of the area in 10 or more increments. Average these measurements to find the radius,

then calculate the area using the formula for a circle.

Example: Approximate the area by calculating

the area of a similarly sized circle.

Volume of Cube and Box Shapes

The volume of a cube or box is found by multiplying the length, times the width, times the

height.

(Length) x (Width) x (Height) = Volume

Example: (100 feet) x (50 feet) x (30 feet) = 150,000 cubic feet

Volume of Cylindrical Shapes

The volume of a cylinder is found by calculating the area of the round end (see formula for

circle) and multiplying this area times the length or height.

Example: (radius) x (radius) x (3.14) = Area of Circle

(Area of Circle) x (Length) = Volume of Cylinder

(2 feet) x (2 feet) x (3.14) x (6 feet) = 75.36 cubic feet

Sprayer Calibration Formulas:

To Calculate Travel Speed in Miles Per Hour

The travel speed of a sprayer is determined by measuring the time (seconds) required to travel a

know distance (such as 200 feet). Insert the values in the following formula to determine the

miles per hour.

Distance in Feet x 60 = Miles Per Hour

Time in Seconds x 88

Example: (200 feet) x (60) = 12,000 = 4.55 mph

(30 seconds) x (88) 2640

To Calculate the Gallons Per Minute Applied During Broadcast Spraying

The application rate in gallons per minute (GPM) for each nozzle is calculated by multiplying

the gallons per acre (GPA), times the miles per hour (MPH), times the nozzle spacing in inches

(W); then dividing the answer by 5940. For small adjustments in GPM sprayed, operating

pressure is changed. For large adjustments in GPM sprayed, travel speed (miles per hour) is

changed or nozzle size is changed.

GPA x MPH x W = GPM

5940

Example: (12 GPA) x (4.5 MPH) x (24”)

= 1296 = 0.22 GPM

5940 5940

To Calculate the Gallons Per Minute Applied During Band Spraying

Broadcast spraying applies chemicals to the entire area. Band spraying reduces the amount of

area and chemicals sprayed per acre. To use the above formulas for band sprayer applications,

use the band width (measured in inches) rather than nozzle spacing for the “W” value.

Pesticide Mixing:

Terminology

The active ingredients of a pesticide are the chemicals in a formulation that control the target

pests. The formulation is the pesticide product as sold, usually a mixture of concentrated active

ingredients and an inert material. Restricted use pesticides are purchased in formulations

requiring dilution prior to application. Formulations are diluted with inert substances such as

water. The percentage of active ingredients in a pesticide formulation directly affects dilution

and application rates. Given two pesticides, A = 50% active ingredients, B = 100% active

ingredients; twice as much pesticide A formulation is required to equal pesticide B formulation.

To Determine the Total Amount of Pesticide Formulation Required Per Tank

To calculate the total amount of pesticide formulation needed per spray tank, multiply the

recommended dilution, ounces/pints/cups/teaspoons/tablespoons/etc. of pesticide per gallon of

liquid, times the total number of gallons to be mixed in the sprayer. A full or partial tank of

pesticide spray may be mixed.

(Dilution Per Gallon) x (Number of Gallons Mixed) = Required Amount of Pesticide

Formulation Example: (3 ounces per gallon) x (75 gallons) = 225 ounces

Note: 1 gallon = 128 ounces; through unit conversion 225 ounces = 1.76 gallons

To Calculate the Amount of Pesticide Formulation Sprayed Per Acre

The calculate the total amount of pesticide formulation sprayed per acre is determined by

multiplying the quantity of formulation (ounces/pounds/pints/cups/teaspoons/tablespoons/etc.)

mixed per gallon of water, times the number of gallons sprayed per acre.

(Quantity of Formulation Per Gallon) x (Gallons Sprayed Per Acre) = Formulation Sprayed Per Acre

Example: (1/2 pound per gallon) x (12 gallons per acre) = 6 pounds per acre

To Calculate the Amount of Active Ingredients Sprayed Per Acre

To calculate the total amount of active ingredients (AI) applied per acre, multiply the amount

(pounds, gallons, ounces, etc) of pesticide formulation required per acre, times the percentage of

active ingredients in the formulation (100%, 75%, 50%, 25%, etc.), and divide the value by 100.

(Amount of Formulation Required Per Acre) x (Percentage of AI)

= Active Ingredients Per Acre

100

Example: (4 pounds formulation sprayed per acre) x (75% AI) = 3 pounds of AI sprayed per acre

100 Note: 75 % = 0.75

To Calculate the Gallons of Pesticide Mixture Sprayed Per Acre

The calculate the total amount of pesticide mixture sprayed per acre is determined by dividing

the number of gallons sprayed by the number of acres sprayed.

Gallons Sprayed = Gallons Sprayed Per Acre

Acres Sprayed

Example: 200 Gallons Sprayed

= 20 gallons of pesticide mixture sprayed per acre

10 Acres Sprayed