Wild blackberries are difficult to control and often require follow-up treatment since plants are capable of regenerating from the crown or rhizomes. A combination of mechanical and herbicide treatments followed by a prescribed burn to remove vegetation is often more effective than a single treatment.
Herbicide application from mid-summer (after bloom) to early fall before the first frost will optimize control. Herbicides applied prior to flowering generally result in removal of top growth and limited control of the root system. Apply Opensight at 3.3 ounces product/acre (oz/A)/A, or Milestone plus Garlon® 4 Ultra (5 fl oz/A+2 pt/A) to blackberry after bloom and before frost. For blackberry plants that have been mowed, shredded or burned, delay herbicide applications until the following growing season. This allows blackberry plants time to re-grow for optimum uptake and translocation of the herbicide.