Ryegrass Most Damaging Weed in Winter Wheat

Ryegrass is the probably the most damaging weed to winter wheat over a large part of the high rainfall area in the central, north and east Texas. Economic losses in wheat occur through reduced grain yield, quality, foreign matter, and harvest efficiency. Yield loss can exceed 90% in heavy infestations. In addition to yield reduction, reduced harvest efficiency results in lower test weight, high grain moisture content and high foreign matter content. Because of the great quantity of seed found in infested fields, a relatively wide window of germination, a prolific root system, and the propensity of the clay soils in east Texas to remain wet over a large period of time, mechanical control is impractical. Herbicides, crop rotation and crop management remain the most effective control measures. For fields with a history of ryegrass infestation, control programs should be planned well before the fall seeding of winter wheat. Perhaps the best control procedure is crop rotation in conjunction with the use of alternate herbicide families. Farmers should consider planting a grain crop such as corn or sorghum that is tolerant to atrazine. This will allow land preparation in the fall followed by the application of one pound of atrazine as an over-wintering weed control to suppress broadleaf weeds and ryegrass emergency. This program should keep fields clean over the winter and allow establishment of the sorghum or corn crop without competition from ryegrass. A second potential management scheme would include delayed planting to allow a good flush of ryegrass to emerge followed by the use of burndown herbicides such as Roundup or paraquat in a stale seedbed before planting. This technique assumes germinating rainfall will occur before the wheat planting date. Allow adequate time for these herbicides to control the newly emerged ryegrass, and then sow wheat with a drill equipped with double disk openers to minimize the exposure of new ryegrass seed to the surface. Any disturbance or inversion of the soil at this time will somewhat negate the efficacy of the burndown treatment rare to the exposure of more ryegrass good from the soil seed bank. In a recent trial at McGregor, ryegrass control in excess of 90 percent was achieved by a Roundup burndown followed by shallow, late wheat planting. Ryegrass can only emerge from depths of approximately 1⁄2 inch or less. If the major fall flush of ryegrass is controlled without disturbing the seedbed, the overall ryegrass population will be substantially reduced. A third consideration with respect to mechanical management of ryegrass is fertilizer placement. Farmers using phosphorus fertilizer on winter wheat are encouraged to band phosphorus with the wheat seed at planting, enhancing the competitive ability of winter wheat to utilize this fertilizer compared to ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ❚ ★ ★ ★ The Texas A&M University System Texas Agricultural Extension Service