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Tips to Control Spray Drift and Target Weeds

Since herbicide-resistant weeds are increasing, farmers need to plan for more ways to fight off weeds using a variety of methods on different areas. Incorporating diverse methods makes it so that farmers need to pay more attention to how and where they apply herbicides.

When farmers decides to incorporate a variety of weed killers, they need to take special care that the new herbicides don’t hit neighboring crops that may be more sensitive and may be damaged by the herbicides.

Spray drift is what happens when herbicides or other sprays for crops move through the air and hit crops they weren’t intended for. Spray drift is a huge concern for modern farming. For example, an herbicide that blows into a field of unresistant soybean plants may kill the whole field (not to mention, the soybean income).

There are a few ways to reduce spray drift. Weed scientist Dan Reynolds, Ph.D., of Mississippi State University gave four main ways to control spray drift:

  1. Nozzle Selection

Choosing the best nozzle for application can be difficult, but Reynolds says it is the most important step to minimize spray drift. Nozzles are made for specific uses, so keep this in mind when selecting a nozzle for a particular task. Farmers need to consider carefully what jobs they will use the nozzles for, both currently and in the future. Therefore, a farmer should keep a variety of nozzles ready for their different jobs. In conjunction with this, farmers need to read nozzle catalogs and herbicide labels to know how to best calibrate the sprayer systems for each field.

  1. Droplet Size

Smaller droplets are more likely to drift. However, there are a lot of new technologies that help farmers control the droplet size. These include: high-volume air-assisted sprayers, improvements on the nozzles themselves, spray tank additives and electronically-controlled sprayers. Droplet size might help farmers choose an appropriate nozzle, according to Reynolds, but farmers still need to figure the best droplet size to ensure the best application and the least spray drift. “We haven’t been selecting nozzles on droplet size in the past as much, but now it’s important based on the sensitivity of crops to off-target deposition,” he said.

  1. Application Speeds

According to Reynolds, chemical companies will more strongly enforce application speed restrictions. “When the speed is too low, that’s when droplets will be suspended in air and move for long distances. When speeds are too fast, physical drift to another area can occur.”

  1. Multiple Practices

A farmer needs a variety of methods to combat spray drift. These may include drift-reduction nozzles and deposition-agent additives. But these options are only helpful if chosen selectively. “This transition will not be a simple thing. A good drift-management plan will include multiple strategies,” he said. “One practice alone does not make for a good plan.”

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