Kearney Agricultural Research and Extension Center EHS
University of California
Kearney Agricultural Research and Extension Center EHS

Minimizing Pesticide Drift

Kearney Agricultural Research and Extension Center (KARE) has adopted the following standard operating procedure (SOP) for agricultural chemical spray applications.

These guidelines that are to be followed whenever any chemical spray application is required on agriculture fields and/or crops.

The procedures here establish uniform guidelines designed to ensure that all agricultural chemical spray applications are performed in such a manner that the possibility of residual drift is minimized. These requirements also are designed to ensure that procedures and practices are in place to safeguard the health and safety of all employees and surrounding research projects.

Operating procedures

The safety of all employees or visitors at the KARE facility should be foremost in any chemical spray application. The applicator shall make a visual observation of the area that the application is to be made. The applicator shall visually check the primeter of the field to assure there is no one in the close proximity. The applicator is ultimately responsible for the prevention of drift.

Use as coarse a spray as possible that will still allow good coverage and control. For sprays, use formulations which give large diameter (150 - 200 microns or larger) spray droplets.  Droplet size is one of the most important factors affecting drift.  Use a larger nozzle and lower pressure to produce a coarse spray which achieves the same rate of application.

Don't apply pesticides under windy or gusty conditions; don't apply at windspeeds over 5 mph. Read the label for specific instructions.

Maintain adequate buffer zones to insure that drift does not occur off the target area. Read the label. Be aware of adjacent crop potential conflict with the label of the chemical you are using.

Choose an application method and a formulation that is less likely to cause drift. After considering the drift potential of a product/formulation/application method, it may become necessary to use a different product to reduce the chance of drift.

Use drift control/drift reduction agents. These materials are basically thickeners and are designed to minimize the formation of droplets smaller than 150 microns. They help produce a more consistent spray pattern and aid in deposition. Some of these are: Chem-Trol, Intac, Lo-Drift, Nalco-Trol, Nalco-Trol II, StaPut, Wind-Fall, and Arborchem 38-F.

Choose the formulation carefully. Water-based sprays will volatilize more quickly than oil-based sprays. However, oil- based sprays can drift farther because they are lighter, especially above 95° F.

Apply pesticides early in the morning or late evening; the air is often more still than during the day. However, be aware of totally stagnant air conditions which may produce a "chemical cloud" harmful to workers nearby.

Don't spray during thermal inversions, when air closest to the ground is warmer than the air above it. When possible, avoid spraying at temperatures above 90°-95° F, ideally not over 85° F.

Use a solid cone or fan spray nozzle. These produce larger droplet sizes than hollow cone nozzles.

Check your system for leaks. Small leaks under pressure can produce very fine droplets.

Determine wind direction and take this into account in determining application timing, equipment and whether or not to make an application. The wrong wind direction can cancel out everything else you have done to reduce drift.

For applications of liquid and dry formulations, shrouds or skirts attached over or behind the application equipment can help prevent spray droplets and pesticide particles from becoming airborne.

The use of air blast sprayers in orchards is a highly visible application method with significant potential for drift problems.  Be sure the machine is properly adjusted to direct the spray into the tree canopy. On most sprayers, one or more of the upper nozzles will not deliver spray to the tree and should be shut off. Use only the nozzles that actually deliver spray to the tree.

For ground rigs and hand sprayers, use low pressures and don't spray too close to the target surface to reduce spray-back aerosol.

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