Keeping crop protectant applications on target continues to be at the forefront of farmers' minds, as well as the people neighboring the fields.
As most already know, wind often can derail your plans for spraying. Keep in mind that the objectives of any spray application are to balance productivity and efficacy, and to 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 - whether it's nozzle selection, ground speed, pressure, different pesticide formulations, adjuvants or something else - will ultimately affect droplet size, potential drift and possibly efficacy.
In some situations, reducing spray drift can be easier said than done. Below are 10 things you should consider to keep the product on target:
1. Spray during low wind. In general, winds are less of an issue early in the morning or late in the evening. But strong winds can prevail for a few days, keeping you out of the field.
Also, read the label carefully because other factors may need to be considered. Certain products such as Enlist One and dicamba are susceptible to drift during temperature inversions, which can occur from evening until dawn. The Liberty (glufosinate) label recommends that it is best to apply between sunrise and two hours before sunset for optimal weed control.
2. Reduce spray 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 they still produce less drift than other types of nozzles. In most cases, contact herbicides like Gramoxone, Liberty, Reflex, Cadet and others should be applied through nozzles that produce medium-to-coarse droplets.
Thus, some of the newer drift-reducing nozzles might not provide the best spray coverage for effective weed control. However, increasing spray volume can help to improve coverage, but that could mean using a nozzle with a larger orifice in order to reduce the pressure.
3. Increase carrier volume or application rates. If possible, use a spray volume of 20 gallons or more per acre, instead of 10 gallons or less per acre.
4. Select proper nozzles with coarse spray droplets. There are several companies that manufacture nozzles designed to reduce drift. Some examples include TeeJet's AI, AIXR and TTI; Greenleaf Technologies TurboDrop XL; and Hypro's Ultra Lo-Drift Max.
After selecting the proper nozzle, the correct speed, pressure and output must be determined and achieved by conducting appropriate sprayer calibration.
5. Use lower spray boom heights. Make sure to use nozzles that have a spray angle of 110 degrees or more. This will allow the boom to be lowered more than nozzles with lesser angles, but it 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.
6. Reduce sprayer ground speed. Faster speeds will cause the boom to bounce and spray vortex to occur, sending spray droplets higher in the air.
7. Use drift retardants. There are many good drift-reducing products on the market for this purpose. However, some are not compatible with certain drift-reducing nozzle types.
Also, spray when the wind is blowing away from sensitive areas. Avoid applications when strong winds blow toward sensitive crops, homes, gardens and the like.
8. Consider buffer zones. This is especially useful if sensitive crops or habitats are in adjacent areas.
Try to include a buffer of at least 250 to 300 feet near sensitive areas. If the buffer is included as part of the production area, treat the buffer with different products that will not affect the sensitive area, or spray that area during a different time to avoid affecting the sensitive area.
Another option is to plant a cover crop in the buffer zone, so there will not be an issue if it's injured or killed by spray drift. To help determine if sensitive crops are in your vicinity, go to the DriftWatch website. Available in many states, DriftWatch is a free, online voluntary specialty crops registry designed to alert applicators of locations of sensitive areas.
9. Read your labels. As new pesticides come to market, or older product labels are updated, it is important to adhere to the Endangered Species Act drift mitigation tactics that are listed on the labels. Some initial examples include Enlist One and Liberty Ultra.
10. Invest in "high-tech" sprayers. Some of the newer sprayers use a pulsing system to assist in better application and drift reduction.
Also, new "spot-spray" boom applicators are making huge strides in the marketplace to not only reduce drift, but also - in some cases - the amount of herbicide being applied. Keep in mind, though, that some of the new sprayers increase pressure to maintain output if the ground speed is increased, thus producing additional fine droplets.
There are other tactics that could be used. But these are the most common ways to reduce spray drift.
