Source: Penn State Extension
The importance of keeping crop protectant applications on target continues to be at the forefront of growers’ minds as well as people neighboring the farms. Making sure the product stays on the intended target is critical for the health of the plant as well as those surrounding the area.
As most already know, wind often can derail your plans to spray. Keep in mind the objectives of any spray application are to balance productivity, efficacy, and prevent off-site movement of pesticides. It is also challenging to find a functional intermediate between controlling drift and not sacrificing herbicide (or other crop protectant) coverage and efficacy.
Any change that is made to the spraying system, such as nozzle selection, ground speed, pressure, different pesticide formulations and adjuvants, will ultimately impact droplet size, potential drift and possibly efficacy.
In some situations, reducing spray drift can be easier said than done. Here are 10 things to consider to help keep product on target:
- Spray at low wind velocities (less than 10 mph). In general, winds are less of an issue early in the morning or late in the evening.
- Reduce spraying pressures. Lower pressures allow for larger droplet sizes. Be aware that nozzles can produce different droplet sizes at different pressures. So a nozzle might produce medium droplets at a low pressure but fine droplets at higher pressures. However, some of the new drift-reducing nozzles are designed to require higher pressures for better spray coverage but still produce less drift than other types of nozzles.
- Increase carrier volumes/application rates. If possible, use 20 gallons or more per acre instead of 10 gallons or less per 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’s AI, AIXR and TTI; and Greenleaf Technologies’ TurboDrop XL and Hypro Ultra Low Drift, among others.
- Use lower spray boom heights. Make sure to use nozzles that have a spray angle of 110 degrees. This will allow the boom to be lowered more than nozzles with lesser angles, but will ensure spray pattern and proper overlap is maintained. In general, for a boom with 20-inch nozzle spacings, maintain a boom height of 24 inches or less above the crop canopy.
- Reduce sprayer ground speed (less than 10 mph). Faster speeds will cause the boom to 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. However, some are not compatible with certain drift-reducing nozzle types.
- Spray when wind direction is away from sensitive crops, homes, etc.
- Consider including buffer zones if sensitive crops are in adjacent fields. Some suggestions include a buffer of at least 250-300 feet near sensitive areas. If the buffer is included as part of the production area, treat the buffer with different products that won’t affect the sensitive crop and/or spray that area during a different timeframe to avoid injuring the sensitive crop. Another option is to plant a cover crop in the buffer zone so there won’t be an issue if it’s injured or killed by spray drift.
- 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. Keep in mind, however, that some of the new sprayers increase pressure to maintain output if the ground speed is increased, thus producing additional fine droplets.