|
|
Controlling volunteer wheat key to crop successBy Larry Dreiling It happens every spring. A hailstorm wipes out a wheat crop just a few weeks short of harvest. Perhaps there's some shattering. Maybe even a late freeze. It just always appears that something bad affects some part of a producer's wheat crop. When it happens, expect the result to be a stand of volunteer wheat in summer and fall. Even if a producer has a good stand of wheat now, it's not too early to plan for controlling volunteer. Recent problems with wheat streak mosaic, High Plains virus, and triticum mosaic virus offer a reminder of the importance of controlling volunteer wheat well before the next year's crop is planted. What sort of damage can volunteer bring onto a wheat crop? Let us count the ways: --Wheat streak mosaic virus, --Hessian fly, --Russian wheat aphid, --Take-all, --Barley yellow dwarf virus, --Banks grass mite, --Chinch bug, --Moisture loss. Many times, these results come from another source that loves to ingratiate itself into a stand of volunteer and then damage the next year's crop down the road, according to Dr. Jim Shroyer, professor of agronomy and Extension crop production specialist at Kansas State University. Simple rules, hard to accomplish Volunteer wheat within a half-mile of a field to be planted to wheat should be completely dead at least two weeks before wheat planting, Shroyer said. This will help control wheat curl mites, Hessian fly, and greenbugs in the fall. "The most important threat from volunteer wheat is the wheat streak mosaic virus complex. These virus diseases cause stunting and yellow streaking on the leaves," Shroyer said. "In most cases, infection can be traced to a nearby field of volunteer wheat, although there are other hosts, such as corn, millet, and many annual grasses, such as yellow foxtail and prairie cupgrass. Control of volunteer is the main defense against the wheat streak mosaic virus complex." Wheat streak mosaic virus is carried from volunteer to newly planted wheat by the wheat curl mite, Shroyer said. Wheat curl mites are white, cigar-shaped, and too small to be seen with the naked eye. The curl mite uses the wind to carry it to new hosts and can travel up to half a mile from volunteer wheat. Those mites are responsible for a host of wheat problems, Shroyer said. "The wheat curl mite is the vector for wheat streak mosaic, the High Plains virus, and triticum mosaic virus," Shroyer said. "In addition, the mite can cause curling of leaf margins and head trapping." Insect woes Another problem resulting from volunteer are Hessian flies, which survive over the summer on wheat stubble. When the adults emerge, they can infest any volunteer wheat that may be present, which will keep the Hessian fly population alive and going through the upcoming crop season. "This insect often causes significant damage, especially in the eastern two-thirds of the state. Hessian fly larvae attack young wheat plants near the soil line. Tillers may be stunted and lodge," Shroyer said. "In heavy infestations, the whole stand may be lost. The Hessian fly normally has a spring brood and a fall brood. In years with a wet summer and/or a long open fall, there can be two broods of Hessian fly in the fall; and this is even more likely where volunteer is allowed to grow and become infested early." Volunteer wheat also is a host of barley yellow dwarf virus, and the greenbugs and bird cherry-oat aphids that carry it. Russian wheat aphids may also live over the summer on volunteer wheat. While this insect has wings and can be wind borne for hundreds of miles, the vast majority of fall infestations in Kansas appear to originate from nearby infested volunteer. More bug problems A number of other insects are also associated with the presence of volunteer wheat. "An example in western Kansas is the Banks grass mite," Shroyer said. "During some years, infestations become established during late summer and early fall on volunteer wheat. "Later, as the quality of the volunteer deteriorates, mites move from the volunteer into adjacent fields of planted wheat or other small grains. Occasionally, mites will survive the winter and continue to spread into the planted wheat following greenup in the spring." A concern in the eastern part of Kansas is the chinch bug. Occasionally, adult bugs will fly from maturing sorghum fields in late summer to nearby fields where volunteer wheat is growing. "Where infested volunteer is allowed to grow right up until seedbed preparation just prior to planting, early planted continuous wheat is likely to become infested. Similarly, volunteer that is allowed to grow through the fall and into the following spring may serve as an attractive chinch bug host," Shroyer said, reminding producers how critical it is that all volunteer must be completely dead within one-half mile of a field. Timing is crucial Another reason to control volunteer is that volunteer and other weeds use up large amounts of soil moisture. When water storage is important, such as in summer fallow, volunteer must be destroyed. "Destroying volunteer after the new wheat emerges is too late," Shroyer said. "You should leave enough time to have a second chance if your control is incomplete. Tillage and herbicides are the two options available for volunteer control." Tillage usually works best when plants are small and conditions are relatively dry. "Tillage is a relatively cheap way to control volunteer," Shroyer said, "but each pass you make reduces the ground cover and reduces your soil moisture even more. "You can use a disc, a field cultivator or a V-blade sweep to control volunteer, but again, you are looking at moisture retention issues." That leaves use of a good herbicide to control volunteer. Options for herbicide use depend on cropping systems and rotations. Glyphosate can be used to control emerged volunteer wheat and other weeds during the fallow period in any cropping system. However, it has no residual activity and will not control later germinating volunteer wheat or weeds. "If glyphosate is used too close to planting time, volunteer may stay green long enough to transmit diseases and insects to the new crop," Shroyer said. "The optimum time to treat with glyphosate is when most of the volunteer has emerged and is healthy and actively growing. Glyphosate can effectively control volunteer wheat that has tillered." Chemical solutions Atrazine is a relatively inexpensive treatment for volunteer wheat control that can be applied anytime in the summer or fall, if rotating to sorghum or corn. In September through October, using atrazine plus crop oil alone can often control small volunteer wheat that has not yet tillered, as well as later-emerging volunteer wheat and other weeds. If the volunteer has tillered, most of the roots will have grown deep enough to be out of the reach of atrazine. This is when it helps to add glyphosate to the atrazine plus crop oil. Glyphosate is translocated from the leaf tissue throughout the plant. "The combination of glyphosate and atrazine plus crop oil will provide a good combination of burndown and residual control on both volunteer that has tillered and later-emerging volunteer. Atrazine rates need to be adjusted to soil type and pH, and may not be appropriate for all areas," Shroyer said. Love thy neighbor A real issue for control of volunteer is neighbor cooperation, Shroyer said. "Even if you control your volunteer, your neighbor's volunteer may come back and hurt your crop. Like the old saying, it's one bad apple that spoils the whole barrel," Shroyer said. "You need good neighbors to make it all work for you in controlling volunteer. If you have a neighbor who doesn't have the time to work on control, you might want to ask to do it for them if they cover the fuel and the chemical bills for them." One last trick in controlling volunteer, Shroyer adds, is working to find what he calls "hidden volunteer." The obvious place to look is in wheat stubble, but other places require producers to search for volunteer. "I've often seen where you miss some along field edges, or along waterways, behind hedge rows and in double-cropped ground," Shroyer said. "Since most all of the problems that come from volunteer are carried along by the wind, you really have to scout for that half-mile around your new field, especially look in the direction of the prevailing winds." For more information on field preparation for wheat, visit www.oznet.ksu.edu/library/crpsl2/c529.pdf to obtain K-State Research and Extension's Wheat Production Handbook. Larry Dreiling can be reached by phone at 785-628-1117 or by e-mail at ldreiling@aol.com.
Copyright/Privacy
Copyright 1995-2011. High Plains Publishers, Inc. All rights reserved. Any republishing of these pages, including electronic reproduction of the editorial archives or classified advertising, is strictly prohibited. If you have questions or comments you can reach us at High Plains Journal 1500 E. Wyatt Earp Blvd., P.O. Box 760, Dodge City, KS 67801 or call 1-800-452-7171. Email: webmaster@hpj.com |
|
