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Weeds in wheat
By D. Bruce Bosley Extension Agent/Cropping Systems Colorado State University Extension Weed problems in winter wheat start during the late summer growing period. Weed seeds germinate and develop before or right when the winter wheat crop is planted. This adaptation allows winter annual weeds such as Downey brome (commonly known as cheatgrass), jointed goatgrass, and volunteer rye to grow right along with the wheat. Skipping tillage in August can help to conserve what little moisture is in the soil, but this also allows weeds to develop undisturbed. The best solution to control weeds in wheat is to rotate out of wheat to a summer row crop. If crop rotation is not workable and a grower is going back into wheat this fall, herbicides are an option. Maverick herbicide can be applied post-emergence in the fall or spring for control of downey brome, but is best used in the fall. Another option for winter annual weed control is to plant a Clearfield wheat variety and apply Beyond herbicide. Two Clearfield wheat varieties were developed at Colorado State University having tolerance to Beyond herbicide. Above was developed for the 2003 planting season, and Bond CL was released last year. Beyond cannot be used on non-Clearfield wheat varieties or the wheat will be severely injured or killed. Beyond provides control of downey brome, jointed goatgrass, feral rye, and mustards. Beyond can be applied post-emergence in the fall or spring, but generally gives the best results in the fall, especially for rye and problem downey brome infestations. Manage wheat insects, diseases now Control volunteer wheat to eliminate the "green bridge" that allows pests to survive the period between wheat crops. Volunteer wheat serves as a reservoir for wheat streak mosaic, High plains mosaic, barley yellow dwarf, and leaf rust. It also harbors Russian wheat aphids and other wheat insect and arthropod pests. The objective is to break the green bridge before the new crop emerges. Therefore, volunteer should be eradicated at least two weeks before planting to ensure a thorough kill. Field border treatments can reduce the spread of insects such as grasshoppers, aphids and greenbugs, and depending on the insecticide can also reduce wheat curl mites. Early planting is also a risk factor for several diseases including wheat streak mosaic, High plains mosaic and barley yellow dwarf. Avoid planting wheat in Northeast Colorado before Sept. 10. Finally hope that adjacent crops and grass areas don't remain green past the end of September. Seed Treatments are excellent for control of seedborne diseases such as common bunt and loose smut. In order to keep our seed supply clean, seed treatments are highly recommended for all seed production fields. Avoid serious wheat pest and disease problems with these simple but very effective clean up. Tillage and herbicides can both clean up fields and field margins but herbicide treatments are better at conserving soil moisture and providing erosion protection. Give your wheat plantings an early growth boost with late summer no-till herbicide treatments. Please contact me about this article or other cropping systems or natural resource topics at 522-3200, extension 285 in Sterling or 542-3540 in Fort Morgan. Date: 8/29/07
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