Newsroom

McMINNVILLE - Vapors from some popular herbicides are drifting far and damaging commercial vineyards and residential landscapes in western Oregon, according to Susan Aldrich-Markham, agronomist with Oregon State University Extension Service.

Well-meaning homeowners who spray weedy blackberries and brush may not realize that the herbicide they are using can drift as much as a mile beyond their property, damaging valuable shrubs, trees and vineyards along the way, said Aldrich-Markham.

"Every year, we detect some damage to our vineyard from herbicides that have drifted in from elsewhere," said Mark Huff, owner of Stag Hollow Vineyards near McMinnville. Grapes, in particular, are extremely sensitive to herbicides containing phenoxy-type active ingredients. Other sensitive plants include maples, tomatoes, roses, elms and many ornamentals.

Phenoxy herbicides are broad-leaf weed killers that are sold widely to homeowners. They include active ingredients such as 2,4-D, dicamba, triclopyr, or clopyralid.

"These herbicides are sold under many trade names, so be sure to check the label on the package for the list of active ingredients in the same way that you might consult a nutrition label on the food you buy," advised Jed Colquhoun, weed scientist with OSU Extension Service.

Phenoxy herbicides come in two formulations, ester-based and amine salts. The ester formulations are much more volatile than salt formulations and therefore more prone to drift. When temperatures go above 75 degrees, the ester-based chemical can evaporate and drift as vapor. Even a few days after spraying, these ester-based phenoxy-type herbicides can still release vapor from the leaf surface of the sprayed weed, according to Aldrich-Markham.

Unfortunately, it is on those warm days of spring and summer that homeowners feel most inspired to get out in the yard and clean up weedy blackberries and poison oak.

For blackberry control, Aldrich-Markham recommends spraying during the fall, after temperatures have cooled. A safer herbicide for areas near vineyards is triclopyr as a salt formulation. Products with this formulation are not as widely available as the ester-based phenoxy herbicides, however. Glyphosate, the active ingredient in Roundup, is a non-phenoxy herbicide that also works well to control blackberries and poison oak when sprayed in the fall. However, glyphosate is a non-selective herbicide, which means that it will damage or kill most plant species that it contacts.