Using the proper application method, timing and chemistry improves the odds for success in controlling weeds and woody plants in pastures and rangeland.
Plant identification is a good first step, according to John Boyd, University of Arkansas Extension weed scientist. Boyd discussed managing difficult to control weeds during the annual Ag Technology Conference in Commerce, Texas.
Boyd said pasture and rangeland managers should delay spraying weeds after mowing so plants have adequate foliage to take up herbicides.
“Application method is important,” he said. “With both perennial and woody plants, managers have to do a good job of application.”
Individual plant treatment may be the best option for many locations. “You get better coverage and put more herbicide on the target,” Boyd said. “You also can be more selective and with little risk of drift to non-target plants.”
He said individual plant treatment may be cheaper or more expensive, “depending on infestation levels.” A brush population of less than 400 stems per acre at less than eight feet tall is a good target for individual plant treatment, he said.
Boyd said a backpack sprayer is a good place to start with equipment selection and said these sprayers are better than they used to be. Improved valves are more accurate and operators control pressure more easily.
“A backpack sprayer is feasible even with fairly large acreage,” he said.
For larger areas, however, a four-wheeler with a spray tank may be more efficient. Boyd says a manager may equip a four-wheeler with a tank, pump, filter and hand gun.
Marker dye also may be useful to prevent over-spraying and skipping plants but he warns that some herbicides, Remedy Ultra, for instance, may not mix with the dye.
“Also, use a surfactant for leaf applications to reduce surface tension. Without it, the spray tends to bead up.”
Boyd said Remedy Ultra plus oil offers a good option for basal stem and stump treatments. “Mineral oil is less smelly and less messy than diesel,” he said.
For basal stem treatment, he recommends applying the material to stems less than four inches in diameter. “It's more effective on trees with smooth bark. Treatment can be accomplished anytime but late winter or early spring is best.”
He recommends a mixture of 75 percent mineral oil and 25 percent Remedy Ultra. “With rough bark, take more time to thoroughly wet the bark.”
Boyd said managers should invest in good nozzles for spray equipment. “Brass costs from $10 to $12 each; plastic runs from $5 to $6. Larger diameter nozzles apply materials more quickly; smaller ones deliver a fine mist and material goes further. Also, screens help prevent clogging.”
He said soil application works for some species and offers low cost, durability and accuracy.
For stump treatment, Boyd recommends application as soon as possible after cutting with the 75 percent oil and 25 percent Remedy mixture. “For big stumps, treat the perimeter; for small ones, treat the entire surface.”
He said a “hack and squirt” method also works for tree control. Managers use a small axe or hatchet to cut into a small tree and then apply a herbicide to the cut. He said Grazon P+D, Roundup, or undiluted Arsenal are control options.
He said certain materials work best on particular trees and hard-to-control plants.
For red cedar Boyd recommends Tordon 22K or Velpar L. “These are best on small plants. Soil applications are not as effective on clay soils.”
He recommends a leaf spray of Grazon P+D, Surmount or Tordon 22K for persimmon. May through June is the best time to apply. “Soil application is typically more effective,” he said. Apply Tordon 22K, undiluted, 2 to 4 cc per inch of stem diameter, from March through May.”
For winged elm, Boyd recommends three-fourths ounce of Spike 20P per 100 square feet. “Be aware of valuable plants nearby.”
Surmount or Grazon leaf spray may take care of black locust. For low volume basal stem application, a 25 percent Remedy and 75 percent oil mixture is recommended.
Grazon P+D, in a 1 percent spray solution is recommended for honey locust.
Boyd recommends delaying spray application for wild rose until it grows three to four feet after mowing. “It needs foliage to intercept the spray. Surmount or Grazon P+D are recommended.
Cimarron Plus, Clean Pasture, Remedy or Pasture Guard may take care of blackberry or dewberry plants. Boyd recommends spraying at full bloom and repeat if necessary.
Horse nettle is a problem. “We have no 100 percent control option for horse nettle,” Boyd said. “It has deep roots. Grazon P+D may be the best. Add a surfactant and apply from mid-bloom through fruiting.”
Broadcast Remedy Ultra at a low rate to Osage orange trees less than 10 feet tall or use spot treatments of 1 percent Grazon P+D plus 0.25 percent Remedy Ultra, Boyd said. He also recommends Surmount or Pasture Guard. “We have a lot of options.”
For prickly pear, Boyd recommends Surmount or Tordon 22K.
“For green brier, good luck,” he said. “It's hard to control.” Pasture Guard should take care of sericea lespedeza.
“Hickory is also difficult. Remedy is not perfect but is pretty good. Sassafras is tough, too. Try Grazon P+D or Surmount.” He recommends Spike for oak and says controlling sumac “is easy with 2, 4-D, Remedy or Grazon P+D.”
Boyd said brush control is an ongoing process in pastures and rangeland. “It's not permanent and needs regular updates.”
He also recommends a Texas A&M publication Brush Busters as a good reference.