Each year, homeowners and gardeners turn to herbicides to combat weeds in their lawns and gardens. Occasionally, herbicides may cause unintended damage to plants in the landscape. This can occur when the applicator applies the herbicide too close to desirable plants. However, damage may also occur when herbicides unintentionally move away from the targeted application area due to drift or volatilization.
Drift occurs when spray droplets are blown off target by the wind during an application. Wind speed is the primary factor that influences drift. The higher the wind speed is, the greater the potential for drift to occur. In general, herbicides should be applied when wind speeds are between 3 and 7 mph but never over 10 mph. If it is too windy, wait to make the application when the wind is calmer. Additional ways to reduce drift include using lower sprayer pressure, nozzles that allow for larger droplet size, and hooded sprayers.
Volatilization occurs after an application. The herbicide converts to a gas and rises into the air, where it can be blown off target. Volatilization is most likely to occur when the weather is hot and humidity is low. 2,4-D and dicamba are common broadleaf herbicides that may volatilize when conditions are favorable. To reduce the risk of volatilization, avoid making 2,4-D and dicamba applications during the hot South Carolina summers.
Sprayer contamination is another common way for herbicide damage to occur. This results from failing to thoroughly clean out a sprayer following herbicide applications. Any herbicide residue that is left in the sprayer may cause damage the next time the sprayer is used. When cleaning sprayers, be sure to use clean water to rinse the tank, lines, nozzles, screens, pumps, filters, etc. Rinse everything thoroughly at least three times. Tank cleaners may be required when using certain herbicides, so check for that on the product label. In addition, clean out sprayers immediately following any pesticide application.
For more information on reducing herbicide damage, see HGIC 2349: Herbicide Damage to Landscape Plants.