Blackberries if left unchecked can quickly spread in a pasture and reduce the amount of grazeable acres. The same competitive characteristics which make blackberries relatively easy to grow in a home or commercial setting make them a persistent foe in your pasture or rangeland.
If you plan on spraying blackberries, DO NOT, and I repeat DO NOT mow or burn them for 2 years prior to spraying! Chemical control is most effective during bloom and fruit set stages of growth. This is when they are most susceptible to chemical uptake and translocation.
Blackberry is a perennial, thicket-forming shrub which is very invasive in our area. Each plant has a large lateral-growing root system that can sprout and produce additional plants. The rhizomatous root system is perennial, while the aboveground canes are biennial (living for two years). The first year, the canes or “new wood” emerge and grow rapidly; the second year, the canes bud and produce flowers and fruit. The canes subsequently die after fruiting. This root system is what makes them so competitive and difficult to control.
Currently, several herbicides list blackberry on their label. The most effective herbicides are those which contain metsulfuron or triclopyr ester (Remedy Ultra, others). PastureGard HL (triclopyr + fluroxypyr) and triclopyr ester (Remedy Ultra, others) can safely be applied when blooming, but retreatment the following year will probably be required to achieve control near 100%. Remedy Ultra is very effective at a 1% solution for spot treatments, or 1-2 pints/acre for a broadcast treatment. Good control is dependent on good soil moisture and actively growing plants. Glyphosate is also effective as a 1-1.5% solution for spot-treatments. I have also had good luck using Tordon or Velpar as undiluted spot treatments, applied to the soil in a grid, on 5 ft. centers, at a rate of 9ccs per spot.
These herbicides cause rapid blackberry defoliation and are effective at controlling other weed and brush species. Complete blackberry eradication is probably not possible but acceptable results will likely require multiple applications/years and/or tactics.
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