![]() Tillage can be used effectively in killing weeds and preparing a seedbed for perennial grasses and/or legumes. Weeds must be controlled in CRP acres by tillage, herbicides, crop competition, fire, and mowing or a combination of these methods. These examples point out why weed control on CRP acres deserves serious consideration as a means of reducing problems to adjacent cropland. This could be a bigger problem since the volunteer winter wheat will not be killed by frost. ![]() From there they may move to the seeded winter wheat field. Third, the mites may live on the summer annual grass weeds on CRP acres (planted or scheduled to be planted), and then move to volunteer wheat in adjacent fields. However, if frost occurs late, the mites may have time to move to the emerging winter wheat plants. If a killing frost occurs before the fall-seeded winter wheat emerges, there will probably be little carryover of mites and viruses from the grass weeds to the fall-sown wheat. These grasses could host the wheat curl mite. With no crop to offer competition to weed seedlings, grass weeds easily establish unless they receive competition from large broadleaf weeds. Second, consider land not being cropped and scheduled to be planted to grass for CRP. Summer annual grasses are usually the greatest problem in winter wheat not planted at the optimum time and in spring-planted small grains. With good stands of winter wheat, grass weeds usually have difficulty establishing because of crop competition. The mites could move from the winter wheat to the grass weeds and then to the volunteer wheat. First, consider a wheat field where a lot of grass is established before the crop matures. There are several possible scenarios on how some of the annual grass weeds could be a contributing factor to virus disease problems. Since the wheat curl mite cannot survive without feeding on living grasses, control measures should be taken to eliminate volunteer wheat and host grass weeds. The worst infection by any of the three viruses on winter wheat occurs when the crop is infested by mites in the fall. Cropland converted to the CRP may contain volunteer cereals and summer annual grass weeds which could host the mites and viruses. As the wheat crop matures and dries down, the mites move to the volunteer wheat which can act as a green bridge, providing an opportunity for the mites to infest fall-sown wheat and transmit WSMV, HPV, or TriMV. If there is a hail storm when winter wheat is in the soft to medium dough stage or just before harvest, the shattered grain germinates into volunteer wheat. Wheat curl mite populations in a wheat crop build to high levels during heading because the head provides protection and numerous feeding sites for the mites. Wheat is the preferred host for the wheat curl mite, but the mite can survive on other grasses such as jointed goatgrass, downy brome, crabgrass, Canada wildrye, green foxtail, yellow foxtail, sandbur, stinkgrass, witchgrass, and barnyardgrass. The level of damage caused by HPV or TriMV is not known. Wheat streak mosaic virus can cause up to 100 percent yield loss. These mites are vectors of three viruses that cause disease in wheat: wheat streak mosaic virus (WSMV), high plains virus (HPV), and Triticum mosaic virus (TriMV). Small grains - including wheat, oats, rye and barley - act as hosts for wheat curl mites. Much of the land bid into the CRP is in the small-grain-producing areas of Nebraska. In addition, rapid-growing, uncontrolled weeds can form a canopy which shades slower growing desirable plants and prevents the formation of desirable protective ground cover. Weeds can quickly and thoroughly consume soil water throughout the upper soil profile and must be controlled to allow grass and legume seedlings to germinate and emerge. Soil moisture must be available for seed germination, seedling emergence, and establishment to be successful in getting stands of grasses and/or legumes. Weeds should be controlled on CRP acres to reduce the risk of seeding failure and eliminate possible reseeding costs. Weed control information provided in this NebGuide applies to any cropland that is being converted to permanent vegetation through CRP and other USDA programs or as an effort by a landowner. 23, 1985, as part of the Food Security Act of 1985, encouraged farmers to stop growing crops on highly erodible cropland and plant perennial grasses or trees through a 10-year contract with the U.S. The Conservation Reserve Program (CRP), enacted Dec.
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