John C. French Sr., Retired, Universities:Auburn, GA, Clemson and U of MO, Bugwood.org
Penn State Weed Science has some tips to reduce herbicide drift and keep your herbicides on target.
Along with the cool spring and slow start to growing season, there have been many days with windy conditions. Keep in mind the objectives of any spray application are to balance productivity, efficacy, and prevent off-site movement of pesticides. In some situations, this can be easier said than done. Below are several things to consider to help reduce particle (not necessarily, vapor) spray drift.
- Spray at low wind velocities (<10 mph); in general, winds are less early in the morning or late in the evening
- Reduce spraying pressures; lower pressures allow for larger droplet sizes
- Increase carrier volumes/application rates; if possible use 20 gallons or more/acre instead of 10 gallons or less/acre
- Select the proper nozzles with coarse spray droplets; there are several companies that manufacture nozzles that are designed to reduce drift; some examples include: TeeJet AI, AIXR, and TTI; Greenleaf TurboDrop XL; Hypro Ultra Low Drift, among others
- Use lower spray boom heights; make sure to use nozzles that have 110° or more spray angle which allows the boom to be lowered more than nozzles with lesser angles, but ensure spray pattern and proper overlap is maintained
- Reduce sprayer ground speed (<10 mph); faster speeds cause more boom bounce and spray vortex to occur sending spray droplets higher in the air
- Use drift retardants; there are many good products on the market for this purpose
- Spray when wind direction is away from sensitive crops, homes, etc.
- Invest in "high-tech" sprayers (e.g., pulse modulation); some of the new sprayers use a pulsing system to assist in better application and drift reduction
- Only if absolutely necessary, avoid certain systemic herbicides (2,4-D, dicamba, glyphosate, etc.); if spraying near very sensitive crops (e.g., grapes, fruit trees at "bud break"), selection of other products may be prudent to reduce the concern of serious injury potential; consider burndown herbicides such as Gramoxone, Liberty, Sharpen, metribuzin, or others.