The Importance of CalibrationforPesticide Application

What is pesticide calibration?

Calibration is the process of measuring and adjusting the amount of pesticide your equipment will apply over a target area. It is a critical step in making certain that the application equipment is applying pesticide uniformly and at the correct rate. Correct calibrationof pesticide application equipment saves money and time.

What is the result of incorrect calibration?

Incorrect calibration can lead to:

• Overapplication of pesticide, which is wasteful, costly, and potentially harmful to the environment. Overapplying pesticides also can result in excess residues on or in plants, soil, and surface or groundwater. Furthermore, exceeding the label rate of application is a violation of the law!
• Underapplicationof pesticide, which wastes timeand is costly because it leads to poor pest control and presents the need for re-applying the pesticide.

Why is pesticide calibration important?

Pesticides are applied intentionally to the environment for the purposes of improving environmental quality for humans, domesticated animals, and plants. Therefore, the application of the right pesticide at the right time and proper rate is important to prevent contamination of the environment. To get the correct rate, pesticide application equipment must be properly calibrated and operated.

Types of pesticide application equipment

There are three types of application equipment that are commonly used to apply pesticides. These are: hand sprayers, boom sprayers, and aerial sprayers.

Hand sprayers

Hand sprayers consist of a single nozzle or sometimes a short boom with three or four nozzles. They are used for spot applications of pesticide to small areas. Hand sprayers with a single high-pressure nozzle are used for right-of-way spray operations, ornamental spraying, and spot treatment of noxious weed patches.

Examples of hand sprayers include:

• Compressed air sprayer, or knapsack sprayer, which is used to apply pesticide in small areas including lawns and spot spraying weed patches.
• High-pressure handgun which is a single nozzle high pressure hand sprayer that is used in spot spraying of weeds.

Pesticide applicators should pay strict attention to correct calibration of hand sprayers because overapplication of pesticides is a common occurrence with this type of equipment.

Boom sprayer

The boom sprayer is the most commonly used piece of equipment for the application of pesticide in largescale farming. This sprayer consists of one or two arms of a boom with multiple spray tips that are evenly spread out along the boom and pointed down towards a target.

An alternative to the boom sprayer is the boomless sprayer which has one or two nozzles than can be pointed out sideways or tilted straight up and spray out further to achieve more coverage.

Aerial sprayer

Aerial sprayers are used to spray crops with crop protection products from an agricultural aircraft. Thus, aerial pesticide application is a method of top dressing a pesticide on to an emerged crop while eliminating applicator’s physical contact with soil and crops.

Aerial sprayers are used for pesticide application over large areas of crops and forests that need to be treated rapidly when access is difficult for ground equipment. Fixed and rotary-wing aircrafts equipped with sprayers are the primary equipment used for applying pesticides. Remote controlled helicopters have been used in some instances.

General steps in pesticide equipment calibration

Whereas hand sprayers are easier to calibrate than boom sprayers or aerial sprayers, there are some general steps that are applicable to calibrating most sprayers. These are:

1. Make sure that the sprayer and its parts are in proper working condition. Inspect the spray tank, hoses, nozzle(s), pumps, strainers, and agitators for any leaks or defects. Repair or replace defective parts.
2. Mark off a test area which will be used for a calibration run to determine how much spray solution the sprayer will deliver.
3. Determine the pressure for the spraying – which is not always possible with hand sprayers but is possible with boom sprayers and aerial sprayers.
4. Using water in the tank as the spray solution, select the pressure and speed of delivery and apply the spray in the test area. A constant speed can be set for boom and aerial sprayers.The speed of delivery with hand sprayers is walking at the same speed that will be used when the pesticide will be applied.
5. Record the time it takes to spray the test area.
6. Using a suitable measuring device, collect and measure the spray from the nozzle(s) in the same time it took to spray the test area.
7. Using the amount of spray captured, the per acre application rate can be determined to ensure that the proper rate of pesticide and spray volume are delivered.

There are many aspects involved in applying pesticides to mitigate a pest problem. Central to all these aspects is proper calibration of the spray equipment to deliver the pesticide at the effective rate.

Further Reading

• Chemical Weed Control

References

• Bohmont, B.L. 2007. The Standard Pesticide User’s Guide – 7^th Pearson Prentice Hall. Pp. 335-362.
• Roberson, G. 2000. Calibrating a backpack sprayer. NC State Univ. Extn. Publ. AG-576. https://content.ces.ncsu.edu/calibrating-a-backpack-sprayer. [Accessed, June 30, 2022].
• United States Department of Agriculture – National Resource Conservation Service [USDA – NRCS]. 2006. Calibrating boom sprayers. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_035796.pdf. [Accessed, June 30, 2022].