By Duane Friend
Most landowners and farmers are continually being plagued with problems associated with controlling unwanted trees and shrubs and keeping them from becoming established in fencerows, drainage-ditch banks, pastures, rights-of-way, and other non-crop areas. What many people refer to as “brush” may actually be trees and shrubs known by the common names of box elder, locust, red cedar, mulberry, hedge, multiflora rose, soft maple, brambles, honeysuckle, sumac, hackberry, willow, trumpet creeper, or even poison ivy.
During the dormant (winter) season, a basal bark or cut stump treatment may be effective.
The following information comes from Iowa State University Extension forester Jesse Randall.
Basal sprays are very effective on re-sprouting species and can be used to kill cane patches and thickets, as well as large trees up to 6-8 inches in diameter. Oil soluble herbicides are applied in a bark penetrant carrier. The spray should saturate the lower 18 inches of trunk, crown buds, exposed roots and the soil directly around the base of the trees or brush to optimize control. Applications can be made any time of year, although fall and dormant season treatments often are most effective.
Cut stump, girdle, frill hack and squirt, and Hatchet injection methods are very effective on re-sprouting species of any size. Treatment can be made any time of year. However, application made during periods of heavy sap flow in spring may result in poor control or injury to surrounding trees. These treatments are excellent for selectively controlling unwanted trees and thick-stemmed brush without injury to surrounding trees, bushes, and ground cover. However, brushy thickets, canes, and multi-trunk trees are difficult to treat. Treat the plant before the cut-surface dries (within 2 to 3 hours after cutting but preferably within 15 to 30 minutes) for optimum control. Only the outer edge (sapwood-cambium area) needs to be treated. Several products are formulated specifically for cut-surface treatments (Tordon RTU, Weedone CB, Banvel CST). These products usually contain penetrants and dyes, and do not require mixing. A common error when using any of these three methods involves over application of chemical. This wastes the chemical, which can be expensive, and it can lead to flashback in the soil.
Flashback is where the chemical enters the soil around the tree or shrub that you were intending to kill and it kills all plant material in that zone. Some chemicals can sterilize the soil for years and not allow desired trees to establish and grow.
Glyphosate “Roundup” has been shown to be equally effective in cut stump, frill, and hatchetinjections by varying the concentration. A 50/50 mix of Glyphosate andwater is highly effective from August to November, and from November to February a 75/25 of roundup and water spray will control trees.
When using herbicides for brush control, it is very important to read and follow the directions carefully and completely as there may be restrictions associated with grazing periods and harvest clearances, or application to aquatic areas, drainage ditches, etc. Never apply herbicides without reading and following label directions!