Blackberries and dewberries are prevalent in the southeastern United States, where they crop up in numerous species. Both are found along ditch banks, in pastures and in fence rows, and can be troublesome for cattle and lactating cows. While both plants are stubborn and not easy to permanently destroy, there are herbicides that are effective in eradicating them.
Herbicides are materials that are used to control the growth and spread of weeds. Weeds consist of grass-like plants such as dandelions and crabgrass. Many types of herbicides are available, and the type of plant you wish to control will determine the appropriate herbicide to use.
Herbicides for Blackberries and Dewberries
Blackberries and dewberries are considered shrub-type weeds, and both can be a nuisance. Unfortunately, both blackberries and dewberries are resistant to being disposed of, and are known to regenerate after being mowed, burned and treated with herbicides.
The plants can be difficult to control and remove due to their long underground roots, but repeated manual treatments (tillage, bulldozing, burning) and herbicide treatments should be able to keep them at bay.
The University of California's Statewide Integrated Pest Management Program recommends using tebuthiuron (brand name: Spike) directly on blackberries and dewberries. Because it is non-selective in the type of vegetation it can eliminate, it's important to apply it only to the areas you want to clear out. This type of herbicide should be applied in late summer or early fall.
Glyphosate (Roundup) and triclopyr (Blackberry and Brush Killer, Brush-B-Gone) are two herbicides that can be used to target and eliminate blackberries and dewberries during the growing season, which occurs in late spring and throughout the summer.
The University of Florida recommends that you mow the affected areas, wait six months, and then apply the herbicides. Wait about six weeks for the herbicides to work effectively, then mow and remove the dead plants.