Pesticide spray drift isn't good to the last droplet

When spraying pesticides, don't let others get your drift.

"It is bad enough when your drift damages your crops, your lawn or your garden. But when the damage is to your neighbor's field or flowerbeds, then you've got a real problem," says Erdal Ozkan, an Ohio State University Extension agricultural engineer.

Spray drift is one of the more serious problems pesticide applicators have to deal with. Three-fourths of the agriculture-related complaints investigated by the Ohio Department of Agriculture in 2003 involved drift.

"This shows the seriousness of the problem," Ozkan says. "Drift will be even a bigger problem in the future since there is an increase in acreage of genetically modified crops and use of non-selective herbicides for weed control. Even a small amount of these non-selective herbicides can cause serious damage on the crop nearby that is not genetically modified."

Drift is the movement of a pesticide through air, during or after application, to a site other than the intended site of application. It not only wastes expensive pesticides and damages non-target crops nearby, but also poses a serious health risk to people living in areas where drift is occurring.

"Eliminating drift completely is impossible," Ozkan says. "However, it can be reduced to a minimum if chemicals are applied with good judgment and proper selection and operation of application equipment."

Major factors influencing drift include spray characteristics, equipment/application techniques, weather conditions and operator skill and care.

"Conscientious sprayer operators rarely get into drift problems. They understand the factors that influence drift and do everything possible to avoid them," Ozkan said.

Spraying under excessive wind conditions is the most common factor affecting drift. "The best thing to do is not to spray under windy conditions. If you don't already have one, get yourself a reliable wind speed meter as soon as possible. Only then can you find out how high the wind speed is," Ozkan says.

After wind speed, spray droplet size is the most important factor affecting drift. Research has shown that there is a rapid decrease in the drift potential of droplets whose diameters are greater than approximately 200 microns – or about twice the thickness of human hair.

"If operators of sprayers pay attention to wind direction and velocity, and have knowledge of droplet sizes produced by different nozzles, drift can be minimized," Ozkan says. "The ideal situation is to spray droplets that are all the same size, and larger than 200 microns. Unfortunately with the nozzles we use today, this is not on option. They produce droplets varying from just a few microns to more than 1,000 microns. The goal is to choose and operate nozzles that produce relatively fewer of the drift-prone droplets."

Using low-drift nozzles is one of the many options available to growers to reduce drift.

Following are other drift-reduction strategies to keep drift under control:

• Use nozzles that produce coarser droplets when applying pesticides on targets that do not require small, uniformly distributed droplets, such as systemic products, preplant soil incorporated applications and fertilizer applications.
• Keep spray volume up and use nozzles with larger orifices.
• Follow recent changes in equipment and technology, such as shields and air-assisted and electrostatic sprayers that are developed for drift reduction in mind.
• Keep the boom closer to the spray target. Nozzles with a wider spray angle will allow you to do that.
• Keep spray pressure down and make sure pressure gauges are accurate.
• Follow label recommendations to avoid drift with highly volatile pesticides.
• If you are not using low-drift nozzles, try adding Drift Retardant Adjuvants into your spray mixture.
• Avoid spraying on extremely hot, dry and windy days, especially if sensitive vegetation is nearby. Try spraying during mornings and late afternoons. Although it may not be practical, from the drift reduction perspective, the best time to spray is at night.
• Avoid spraying near sensitive crops that are downwind. Leave a buffer strip of 50-100 feet, and spray the strip later when the wind shifts.

"Good judgment can mean the difference between an efficient, economical application, or one that results in drift, damaging non-target crops and creating environmental pollution," Ozkan says. "The goal of a conscientious pesticide applicator should be to eliminate off-target movement of pesticides, no matter how small it may be."