Producers should watch for volunteer wheat problems
Sep 28, 2009 10:34 AM, By Kay Ledbetter, Texas A&M University
September rains bring unwanted growth.
The recent rainfall in the Rolling Plains region of Texas has been followed up with an explosion of volunteer wheat and other weeds in fallow wheat fields, said a Texas AgriLife Extension Service specialist.
“It is essential that we control this volunteer and other vegetation prior to planting wheat,” said Todd Baughman, AgriLife Extension agronomist in Vernon. “Whether in a conventional, minimum or no-tillage program, we need to plant wheat into a good weed- and volunteer-free seed bed.”
Baughman said there are numerous reasons for the control, but the primary one is to control weeds, insects and disease.
“Often along with this flush of volunteer wheat we will have our first emergence of winter grassy weeds such as cheat, rescue grass, wild oat and ryegrass,” he said. “Effective control allows us to get a jump-start on the problem weeds that reduce yield and impact wheat quality.”
Uncontrolled volunteer wheat also will lead to increased insect problems, Baughman said. These include grubworms, aphids, wheat curl mite and Hessian fly. Control of volunteer and other vegetation prior to planting is one of the keys to managing many of these insect pests.
“While we thought we were immune to Hessian fly, we have seen an emergence of this insect problem in the northern Rolling Plains,” he said. “In fact, last year would likely have been a problem if not for the severe drought and spring freezes. We isolated several fields that had an early infection of Hessian fly pupae.”
Hessian fly larvae can survive on volunteer wheat and other grasses and subsequently infect wheat. Baughman said. Uncontrolled volunteer wheat allows the Hessian fly population to build to a more damaging level.
“We have also observed an increase in wheat streak mosaic virus in the Rolling Plains in recent years,” he said.
Wheat streak is vectored by the wheat curl mite, Baughman said. The wheat curl mite is a very small (one-hundredth inch) white, sausage-shaped mite, too tiny to be seen with the naked eye and requires at least 20X magnification for proper identification.
This mite is most active during warm weather and requires a living grass host to survive the summer, he said. The presence of summer grasses and/or volunteer wheat will provide a “green bridge” allowing wheat curl mite to infect subsequent planted wheat.
Conditions most favorable to the wheat curl mite are early and dense stands of volunteer wheat, volunteer wheat that is not destroyed prior to planting wheat, early planted wheat, cool summers with adequate moisture to sustain grass through summer, and warm, dry falls, which are optimum for reproduction.
“The wheat curl mite alone cause little damage in and of itself,” Baughman said. “However it does transmit wheat streak mosaic virus (and High Plains virus) which in worse case scenarios can reduce yield to almost zero.”
Controlling wheat curl mite through the use of insecticides or miticides is not an option, he said. Therefore management systems that reduce populations of wheat curl mite are needed to minimize the problem.
It is best to control volunteer wheat and other vegetation either through tillage or chemically at least two to three weeks prior to planting wheat, Baughman said. Volunteer wheat and other green vegetation needs to be dead for at least two weeks. However, the longer the vegetation is controlled the better and less likely that problems will occur.
“We must eliminate the green bridge between planting and emergence of the subsequent wheat crop,” he said. “For anyone who is tempted to keep their volunteer wheat for grazing or cover, I cannot discourage this practice enough.
“As my old traveling partner, entomologist Emory Boring, used to say: volunteer wheat will promise more and deliver less than most any crop we deal with,” Baughman said.
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