University of Maryland Extension

Weed of the Week - Herbicide Drift

Chuck Schuster

In an attempt to deal with many landscape and turf weed problems, professionals use a wide variety of products. Professionals are always concerned about drift and many modifications have been made over the years to help decrease drift potential.

Good applicators look at wind speed, nozzle type, discharge height, particle size, and pressure.  Applicators have done a good job in reducing drift as is reflected in the number of complaints that MDA receives every year.  Volatilization is another concern each applicator needs to review. This also is classified as a type of drift, but occurs after the product is applied, and the pesticide slowly evaporates into the air from the soil or plant tissue. This volatilization can occur up to days after application. This is no less problematic or dangerous than other forms of drift. Ester formulations are often more of a concern than amine formulations. Checking the label is very important.

Checking the label for restrictions that might include statements “be particularly careful within the drip line of trees and other ornamental species” or “Do not pour spray solutions near desirable plants” is very important.  The roots of trees are often farther from the trunk than the drip line of the crown, and application of chemicals to this area can potentially cause problems. This type of pesticide volatilization is potentially harmful to many desired trees and shrubs and can be avoided at the same time as control of weeds can be obtained. Read the label carefully to avoid any potential application issues.

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