June is usually the best month to control blackberries in pastures and rangeland in the Southern Great Plains. Non-ranchers reading this may wonder why anyone would want to kill a plant that produces such tasty fruit. I like to eat blackberries as well as anyone, but when they encroach into fields, inhibiting forage growth and access to fields, they have crossed the line between desirable plant and weed.
Where blackberry plants are encroaching and need to be controlled, they should be sprayed only after the plants have bloomed and good soil moisture is present. Spraying too early usually leads to poor control and regrowth of plants. To adequately control blackberries, the new wood must have fully emerged. Blackberries only fruit on new wood. Therefore, if the plants have bloomed or have fruit, the new wood is out and the plants are susceptible to herbicides.
The growth status of the plant when it is sprayed is important. A healthy, mature plant is more sensitive to herbicides than one that has been mown or burned and has regrown. For best results, do not spray blackberry plants that have been mown or burned within the past 12 months.
Several herbicides are labeled for and reported to control blackberries. The two we have had the most consistent success with are triclopyr, which is often sold under the trade names Remedy®, Garlon® and Pathfinder II®, and a formulated mixture of triclopyr and fluroxypyr, which is sold under the trade name PastureGard®. Our tests and experience have shown almost 100 percent control when healthy, mature blackberry plants were sprayed with these products after they had bloomed and good soil moisture was present.
Always read and follow instructions on herbicide labels. The label contains a wealth of information about the product, and following its instructions can prevent costly mistakes.