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Corn+Soybean Digest

Drift Too Swift?

If you're not concerned about spray drift, you should be. It's illegal and you are liable for any damage. If you think insurance will cover such a loss, you might want to rethink that position, unless you can document that you've taken every possible precaution to avoid drift, and you have paperwork.

The “chemical trespass” liability issue is driving more and more retailers/custom applicators to routinely add drift control products to every spray tank — as proof to insurers that they are stewards of responsible application.

Every year, more than 2,500 complaints of drift damage are filed with state regulators and agricultural insurers, according to the EPA. And as more ex-city and town dwellers plunk down roots amid working farms, they may not be as forgiving as farmer-neighbors when it comes to errant spray damage.

What's the best advice? Take basic precautions to reduce drift.

  • Know wind speed and direction at all times (most product labels say not to spray in winds of 10 mph and higher).

  • Use low-drift nozzles that create larger droplets (coarse to very coarse, or 250-400 microns).

  • Lower boom height and spray pressure.

  • Add drift control products to your spray mixture as needed.

  • Use buffer strips on field borders, especially adjacent to sensitive areas.

Drift control products, which range from 25¢ to $1.50/acre or more, will definitely reduce the amount of “driftable fines” (smaller droplets that can drift more easily) when used properly, according to university weed scientists and ag engineers. Most agree that they can reduce downwind drift deposits by at least 50%. And that reduction can climb to 80% if you employ the other mechanical precautions.

Granted, this product category is not without its challenges. Bryan Young, Southern Illinois University weed scientist who has tested many drift control products, frowns on the lack of regulation, and that some manufacturers keep ingredients proprietary, making it a challenge to educate growers on product differences — or product similarities under different brand names.

Since there are more than 100 different spray tank additives that claim to reduce drift, how do you know if retailers carry the best products?

“I tell growers to go to trustworthy retailers who stand behind their products, ask them for third-party research results on the additives they sell and ask which products work best for specific tankmixes. If a company believes in its product, they will usually have it tested,” Young says.

Bob Wolf, Kansas State University ag engineer, suggests that growers do a quick test themselves to ensure the drift control product mixes well with their tankmix products — since some products mix better than others. “And make sure the mixture produces a uniform spray pattern given the nozzles and spray pressure you use. Some drift control products will distort the pattern if too high a rate is used.”

Two groups of drift control agents exist, Young says. “The most common are the viscosity agents (spray thickeners) that contain polyacrylamides or polysaccharides (starch from the guar plant). The second group (non-traditional) features non-polymer, oil-based products that produce larger droplets without affecting the spray pattern like the polys,” he says.

“Traditional polyacrylamides, which have been around for decades, will increase the droplet size, but are very rate-sensitive and can easily distort the spray pattern if not used with the proper nozzle or spray pressure. The adjuvant products made with guar since the late 1990s have similar characteristics, but can also improve the deposition of the relatively larger droplets by reducing droplet bounce or shatter on target weed leaves,” Young says.

The latest group of non-traditional products was developed just a few years ago. Some are oil-based products that create medium-sized droplets to help penetrate the canopy to aid deposition and reduce drift.

One of the leaders in this industry is Agriliance, which obtains third-party product tests to help educate retailers and growers. “We conduct at least two years of research before we market our products, and we recommend to growers that they ask their retailer for independent research on the drift control products they sell,” says Al Bertelsen, staff agronomist for Agriliance.

“Since the adjuvant industry is unregulated, with hundreds of products out there and so many small companies involved, it's the big reason we do so much testing,” says Bob Herzfeld, Agriliance business manager. “And we work with universities known for their spray application work to obtain independent third-party research.”

Agriliance offers three different types of drift management products — some containing multiple products (fertilizers or surfactants) so retailers can help growers match the best product to their situation.

“For example, our best product for drift control for crop penetration is InterLock, which is used on 12 million acres in its third year on the market,” Herzfeld says. “It's a unique modified vegetable oil-based adjuvant that reduces the amount of small ‘driftable fines’ droplets (210 microns and less) while aiding crop penetration. The medium-sized droplets greater than 210 microns move faster out of the nozzle into the canopy.”

Bottom line to improve drift control is to start with the nozzle, Young recommends. “Know your nozzle and the droplet size it will produce, then match that to the products you will apply and determine if you need added drift control.”

Herzfeld agrees that nozzles can improve drift control. “We recommend growers need to combine the right nozzle, the right boom height, proper calibration, a well-trained applicator and the right drift control additives.”

On The Web

These Southern Illinois University Web sites offer the best information on available products that help reduce driftable fines (smaller droplets).

Basics of Drift Control Agents:

Deposition (Drift Control) and/or Retention Agents (119 products):

Adjuvant manufacturers

10 Tips To Reduce Spray Drift

To cut spray drift, Kansas State ag engineer Bob Wolf tells growers to heed spray mechanics and the environment first, before you rely on drift control products.

  1. Use a drift reduction nozzle that delivers larger droplets without sacrificing coverage and control.
  2. Buy a larger capacity nozzle that can apply more gallons per acre because it will produce larger droplets.
  3. Calibrate your sprayer.
  4. Select the proper pressure recommended for your nozzle.
  5. Lower the sprayer boom height without sacrificing spray pattern uniformity.
  6. Don't spray when winds exceed 10 mph.
  7. When the air is calm, it could be the result of a temperature inversion that suspends spray droplets that easily drift off-target.
  8. Don't spray when the wind is blowing toward sensitive crops or landscapes.
  9. Select a reasonable application speed (usually 8-12 mph).
  10. Use a drift control additive when needed.
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