tar weed management

Asked August 17, 2020, 4:05 PM EDT

hello- i have on pasture that has been over run with tar weed. a very bad infestation. i have taken my horses off of it it's so bad. what can i do to kill it. keeping in mind that i put my horses on it and i don't want to harm them.

Lane County Oregon

1 Response

Herbicide products containing 2,4-D will help manage tarweed. Spring applications to rosettes or seedling plants will off the best control in most situations. The herbicide label will list grazing restrictions for livestock if there are any required.

If any plants survive the herbicide treatment you may also consider mowing the plants when stalks are elongating, but before flowering. LThis will help reduce additional seed production. Mowing too early in season often results in the plants regrowing.

Hand pulling or digging is also an option as the root system of this annual plant is not robust. However, if you have a large infestation is may not be a feasible.

Typically tarweed establishes in areas of disturbed soils, including overgrazed pastures, fields that have been left fallow, or areas that have been heavily compacted (common with livestock). Enhancing the growth of desirable forages like grasses will help compete against annual weeds, including tarweed. To learn more about pasture and grazing management to help control weeds you may review our introductory online module that is free to access: https://workspace.oregonstate.edu/course/pasture-and-grazing-management