Whether it’s to moderate the amount of pesticide used or protect adjacent crops in the field, growers constantly have to be mindful of spray drift.
“Spray drift is one of the most serious problems pesticide applicators have to deal with. It wastes expensive pesticides, may damage non-target crops nearby, and poses a serious health risk to people living in areas where drift is occurring,” says Erdal Ozkan, professor, food, agricultural, and biological engineering with The Ohio State University Extension.
“The three main reasons to reduce drift are keeping the environment clean, reducing pesticide consumption and cost, and avoiding costly litigations. Spray drift accounts for about half of all non-compliance cases investigated by the Ohio Department of Agriculture,” says Ozkan.
Tips To Minimize Drift
Here are five cost-effective tips Ozkan gives to vegetable producers on how to minimize spray drift.
1. If you can, keep your nozzles as close to the target as possible while still producing a uniform distribution of spray on the target. This doesn’t cost any money as long as it is practical to make it happen.
2. When you’re ready to change nozzles, consider selecting a new set that will lead to fewer extremely small droplets most likely to drift away. Low-drift nozzles are in the market and do a tremendous job of eliminating extremely small drift-prone droplets from the droplet spectrum (see “Choosing The Right Nozzle”).
3. There are chemicals sold in the market that are designed to increase the droplet size when added into the spray mixture. Most of them are some sort of polymer that tends to increase the viscosity and density of the spray mixture which leads to larger droplets. This, however, should be the last defense against drift. First consider the other option such as better targeting of the spray and switching to low-drift nozzles.
4. Use shields that cover partially or fully the distance between the target and the nozzles. There are companies manufacturing and selling such attachments to the boom. Shields prevent small droplets from moving away from the immediate application area. This, however, may not be practical for sprayers with extremely large booms.
5. If there is any doubt about a spraying job that might result in drift, one should wait until there is no longer that element of doubt. Always pay attention to wind direction and magnitude. The best investment you can make is to buy a wind meter that tells you how high the wind velocity is at any given time. Having a wind meter handy will help you avoid a costly problem associated with spray drift.
Choosing The Right Nozzle
Part of a grower’s defense against spray drift is proper selection of nozzles used in chemical application. Richard Derksen, research agricultural engineer with USDA Agricultural Research Service, offers five tips to keep in mind when selecting nozzles for spray equipment.
1. Follow label directions when selecting nozzles. Many labels not only provide information to help determine the size of nozzle needed for an application but also the spray quality that the nozzle will produce.
2. Use the largest droplet size nozzle that will provide the desired spray coverage. Again follow the label recommendations for the amount of spray coverage needed for an application. Larger orifice nozzles lower operating pressure, and nozzles with narrower spray angles tend to produce larger droplets.
3. If using a spray controller, select nozzles that will not change the spray pattern significantly, as nozzle pressure changes as travel speed changes.
4. Air induction or venturi nozzles reduce the risk of spray drift as can simply reducing pressure and using slightly larger nozzles. However, these techniques produce larger droplets which may lead to lower spray coverage.
5. Air-assist boom sprayers can help reduce the drift of small droplets away from the target area. Smaller droplet size nozzles may be able to be used to increase spray coverage without increasing the risk of drift.