Roadsides and Non-crop Areas: Reduction of Herbicidal Drift

Excerpt from 2008 Chapter 18, Publication 75, Guide to Weed Control, Order this publication

Reduction of Herbicidal Drift

In the application of herbicides, especially of the hormone type (2,4-D, mecoprop, dichlorprop, dicamba, etc.) sensitive crops (grapes, tomatoes, turnips, tobacco, beans, carrots, beets, fruit trees, ornamental plants and many others) beyond the area being sprayed can be damaged by vapor or spray drift.

To reduce the danger of herbicidal drift:

1. Use only amine formulations when it is necessary to apply phenoxy herbicides (2,4-D, mecoprop, dichlorprop, etc.) near sensitive, non-target plants.
2. Very slight spray drift with herbicides containing dicamba can be more damaging to soybeans and other crops than equivalent amounts of 2,4-D spray drift. There is also a possibility of dicamba vapor drift from treated plant foliage during high temperatures (in excess of 25°C); thus, use of dicamba containing herbicides should be avoided near sensitive, desirable plants.
3. Use the lowest pressure possible to apply the herbicide. This may mean the use of a dribble bar, Radiarc boom, vibrajet nozzle, Directa-spra nozzle, flood jet or more conventional nozzle tips.
4. Manufacturer's recommendations regarding nozzle spacing and height should be carefully followed. It may be necessary to mount nozzles on skids to keep them at a constant distance from the surface to be sprayed.
5. For roadside spraying various spray additives are available which may reduce spray drift by increasing the viscosity or density of the spray. These materials should be used following manufacturer's directions and observing normal precautions (vehicle speed, wind velocity, proximity to sensitive crops, etc.)

WARNING: These methods and materials can reduce but not eliminate herbicidal drift. In areas near sensitive crops, all normal precautions must be taken. It should be emphasized that extremely low, even invisible, amounts of spray drift can be very damaging to sensitive crops. In some cases, do not spray during the growing season.

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Related Links

• Weeds in Ontario
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• Integrated Pest Management (IPM)
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• OMAFRA Publication 505: Ontario Weeds
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