Applying The Correct Amount
Introduction
One of the most important tasks for a pesticide applicator is making sure that the correct amount of pesticide is being applied to the target site. Applying either too little or too much pesticide can cause problems.
Under dosing is expensive. If you apply too little pesticide, you may not fully control the pest. Sometimes you can repeat the entire application, but that can be very costly in both time and money. In other cases, a repeat application may not be possible, because it would result in an overdose.
Overdosing is expensive. Do not use any more than the amounts listed in the "Directions for Use" section of the pesticide labeling. Using more product than the labeling recommends will not do a better job of controlling pests, and it is illegal. Overdosing may cause damage or injuries, leave illegal residues, and cause you to be fined or to be liable for damages.
Deciding How Much To Apply
Study the "Directions for Use" section of the pesticide labeling to find out how much pesticide you should apply. If the labeling lists a range of possible amounts, use the least amount of pesticide that will achieve good control of the pest.
Mixing, Loading and Calibration Alternatives
You must determine how to deliver the correct amount to the target site. Depending on the type of formulation you choose and the type of application equipment you will use, you may have to do some combination of three basic tasks -- mixing the pesticide, loading it into your equipment, and calibrating the equipment so you will know exactly how much pesticide it is delivering.
- Mixing -- Except for ready-to-use formulations, you must carefully combine the right amounts of concentrated pesticide formulation and diluent to make the needed application-strength pesticide mixture.
- Loading -- You may need to transfer the pesticide into the equipment before it can be applied.
- Calibrating -- For many kinds of applications, you must measure and adjust the amount of pesticide your equipment will apply to the target site.
Calibrating Your Equipment
Most pesticide applications involve equipment that must be measured and adjusted to release the correct amount of pesticide to the target site. To be sure your equipment is releasing the right amount of pesticide, take time to calibrate it carefully and correctly. Recheck it regularly to detect changes caused by wear, corrosion, and aging.
Before you begin to calibrate the equipment, check it carefully to be sure that all components are clean and in good working order. Pay particular attention to the parts that regulate the amount of pesticide being released, such as nozzles and hopper openings.
Study the manufacturer's instructions carefully -- they explain exactly how to adjust the equipment. They often contain suggestions on such things as the appropriate rate of travel, the range of most efficient pump pressures, approximate settings for achieving various delivery rates, and types of nozzles that can be used.
Speed
For some types of application equipment, the speed at which the equipment moves (or is carried) through the target site is one of the main factors in determining the rate of application. For some other types of equipment, you do not need to consider speed when calibrating.
Equipment with gravity-glow dispersal -- Some equipment, such as some granule spreaders, needs to be calibrated only to adjust the rate of flow or delivery. If the speed of the equipment is kept at an even, moderate pace, the amount of pesticide being released per unit area will be uniform.
Equipment with powered dispersal -- If your equipment has a pump or other mechanism to disperse the pesticide, you will need to determine the rate of speed best suited for the type of equipment and for the particular requirements of your application job. Keep the speed as constant as possible during the calibration process and during the actual application. The equipment manufacturer's directions may offer a range of appropriate speeds.
Uniform Release
If the application equipment you will be using has More than one nozzle or hopper, part of the calibration process is to measure the output from each to be sure that they all are releasing the correct amount of pesticide. Note whether the pesticide output from one or more nozzles (or cluster of nozzles) or hoppers is 5 percent more or less than the amount desired.Calibration Methods
No matter what calibration method you use, you will be measuring how much pesticide is being applied in a specific area. Calibration usually requires you to operate the equipment over a pre-measured distance.
The rate of application depends partly on the particle or droplet size, texture, and other properties of the pesticide being applied. Also, the rate of application sometimes depends on the pressure and on the nozzle size or hopper opening. The equipment manufacturer's directions are the best guide to these selections.
Do a Test Application
Calibrate your application equipment by:
- accurately measuring the amount in the tank or hopper,
- operating the equipment over the pre-measured distance while maintaining your chosen speed (if speed affects the delivery rate of the equipment you are using),
- accurately measuring the amount needed to fill the tank or hopper back up to the pre-application level.
Figure the Application Rate
The amount of pesticide dispersed, divided by the distance covered, is the application rate.
Check Calibration Often
Once you have calibrated your equipment, do not assume that it will continue to deliver the same rate during all future applications. Clogging, corrosion, and wear may change the delivery rate, or the settings may gradually get out of adjustment.
Measure Accurately
Carefully measure the amount of pesticide to add. Do not guess or approximate the amount you are adding, and do not add a little extra "just to be sure." Also measure the amount of diluent carefully. Adding the correct amount of concentrate to an approximated amount of diluent can result in a whole tankful of the wrong strength of pesticide mixture. Mix only the amount you have calculated is needed for the application.
If water or another liquid is being used to dilute the concentrate, rinse the measuring utensils with the diluent and put the rinsate into the mix tank. Repeat this three times to be sure all the pesticide is removed from the measuring utensil. Measuring utensils, such as spoons, cups, jugs, pails and scales, that you use with pesticides should never be used for other purposes. Clean them thoroughly after each use and store them with your other pesticide equipment.
Diluting Pesticides Correctly
Some of the pesticides you buy are dilute formulations that are sold at application strength. These often are labeled "Ready-To-Use" or "RTU." But many pesticide formulations that you use are concentrates, which are sold at strengths many times that needed for application. These formulations must be diluted before you can apply them. They are usually powders or liquids. Granules and dusts are rarely sold as concentrates; fumigants and ultra-low-volume formulations are concentrates that are applied full strength.
The pesticide labeling or other recommendations will tell you:
- what to use to dilute the formulation,
- how much to dilute the formulation, and
- how much of the dilute pesticide to apply per unit of area.
Depending on the situation, you also may need to know:
- how much your equipment holds when full or how much mixture you will need to complete the job
- how much mixture your equipment applies per unit of area,
- the size of the site you need to treat.
Authors:
Philip G. Koehler, University of Florida
Robert A. Belmont, Florida Pest Control Association
This file is part of the UF/IFAS Basic Pesticide Training manual (SM-59) which is intended to provide intermediate training to pest control operators. The manual was adapted from a larger manual, Applying Pesticides Properly, which was developed by Ohio State University in cooperation with the Cooperative Extension Service, U.S. Department of Agriculture, and the Office of Pesticide Programs, U.S. Environmental Protection Agency.
Published: March, 1998
