November 14, 2016
Blackberry and dewberry control in pastures is difficult to achieve. The first step is identification of the plant. Blackberries grow upright while dewberries have a low vine-like growth habit. Dewberries also have slender thorns and red hairs on the stem while blackberries have hard, tough thorns and no hairs. Blackberries grow up to 3-6 feet tall, however, dewberries rarely reach over 2 feet in height. Also, the seeds of dewberries are harder and much larger than that of blackberries.
Blackberries are actually easier to control than dewberries.
A combination of mowing and herbicide treatments is best at controlling these weeds. Mow the weeds in the spring. Then allow them to grow until fall. Before the first frost, apply an herbicide to them and do not mow again until spring.
For dewberries, use triclopyr+fluroxypyr or the brand name Pasturegard HL.For blackberries, use herbicides with the active ingredients: triclopyr + fluroxypyr, triclopyr ester, or chlorsulfuron. Some brand names would include Pasturegard HL, Remedy Ultra and Telar. You can use generic herbicides as long as the active ingredient is the same.
Remember to wait at least 6 weeks after applying the herbicide before mowing.
For more information, refer to Blackberry and Dewberry: Biology and Control.