Timely spring pesticide applications can be a real challenge. Excessive rainfall and wet soils have delayed field work. When it finally starts to dry out, there will be a rush to try to make up for lost time. Applicators need to resist the temptation to make spray applications in unacceptable conditions.

"Misapplication of pesticides continues to be a major concern, and spray drift is a major form of misapplication," says Dennis Epplin, University of Illinois Extension crop systems educator. "Drift is a concern because it removes the chemical from the intended target, making it less effective. Another critical concern is that the off-target movement of pesticides can damage susceptible vegetation and contaminate the environment."

Equipment factors such as nozzle type, size, orientation, pressure, and height of release affect particle drift. Newer electronic rate control systems are helpful but still need to be operated within the design specifications. Deposition (drift control) and/or retention additives help in the proper situation. There are probably well over 100 commercial drift control products available. Bryan Young, SIU Carbondale, has an excellent publication on adjuvants, www.herbicide-adjuvants.com/

Epplin says weather conditions can have a major impact on the amount of off-target drift. Factors affecting drift include wind speed and direction, temperature, relative humidity and atmospheric stability. Wind speed is usually the most critical factor of all meteorological conditions affecting drift. The greater the wind speed, the farther small droplets will be carried off target. Determining the wind direction relative to sensitive crops is important in attempting to minimize damage from drift. The presence of sensitive vegetation downwind often is overlooked by applicators.

"Leave a buffer zone at the downwind edge of a spray area to reduce the potential for damage to sensitive plants," advises Epplin.

When making spray applications, you cannot control the weather. Wind, temperature and humidity can all affect the spray application and increase the potential for drift. You also cannot control the presence of susceptible crops or other non-target areas of concern near your application site. But, what you can do is have the correct equipment and proper weather conditions before making a spray application to ensure your spray stays on target.