How to dash drift
Drift has always lurked as a potential threat to applicators as they put pesticides on crops. It will increase, though, due to these factors.
- Less use of glyphosate-only applications on glyphosate-tolerant crops. Glyphosate is a systemic herbicide. Although glyphosate can drift, applying it in larger droplets can help curb its drift potential while still giving satisfactory control. Currently, 13 glyphosate-resistant weeds have surfaced in 31 states. This will lead to the use of alternative chemistry, some of which may have more drift potential.
- New people in your neighborhood. Former city residents now residing on country acreages likely won't tolerate tomatoes in their gardens getting dinged by off-target pesticides.
- New crops and farmers. You may farm next to organic farmers, whose livelihood depends on being able to prove their products are pesticide-free.
“There is an ever-increasing and ever-important vineyard culture (in the Midwest),” says Mike Owen, Iowa State University (ISU) Extension weed specialist. “When you go east, the vegetable culture is increasing.”
Growth regulator herbicides like dicamba (active ingredient in Banvel and Clarity) and 2,4-D are particularly damaging to grapes at fractions of labeled application rates. For example, current 2,4-D formulations can damage grapes at 100 times lower than labeled rates, according to Purdue University data.
“When you fight marestail with 2,4-D, it can be a real issue if you have lots of vineyards in the area,” says Chuck McDonald, seed and chemical specialist for Wabash Valley Service Company in Oblong, Illinois.
“Today, we have few drift complaints due to Roundup Ready,” says Jim Reiss, vice president of agricultural chemistries business for Precision Laboratories. “This will increase when more chemicals are mixed. We have been lulled to sleep in the way we spray.”
Following are four recommendations to minimize drift.
1. Know Droplet Size
Bear in mind that fine droplets are more prone to drift than more coarse droplets. Chris Boerboom, formerly a University of Wisconsin Extension weed specialist who's now a North Dakota State University administrator, points to research comparing the travel path of a fine 100-micron droplet to a coarse 400-micron droplet.
“The fine droplet took 10 seconds to settle 10 feet; the coarse droplet took two seconds,” says Boerboom. “When wind was applied to the droplets, the fine droplet moved 44 feet to the side. The coarse one moved only 9 feet.”
Today's herbicide labels are specifying the droplet size to use. For example, Liberty's label says to use nozzles that create medium-size droplets between 300 and 400 microns.
2. Watch the Wind
Keep the following factors in mind when spraying regarding wind.
- Know where sensitive areas are, such as vineyards, says Bob Wolf, retired Kansas State University Extension application specialist who now operates Wolf Consulting & Research, LLC.
- Do not spray at any wind speed if the wind is blowing toward these areas. Spray only when prevailing winds blow in a safe direction between 3 mph and 10 mph.
- Don't spray during dead calm conditions. This is fertile ground for drift via temperature inversions to occur.
- Beware of light winds between 0 mph and 3 mph. They can be unpredictable and can quickly change.