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Potential wheat disease outbreak requires immediate action by producers

Recent rains have set the High Plains up for a potential disaster if wheat producers do not take time to destroy volunteer wheat before the drilled wheat begins to come up, said Texas A&M AgriLife experts.

Dr. Charlie Rush, Texas AgriLife Research plant pathologist, said the wheat curl mite, which transmits wheat streak mosaic and other viruses, over-summers on the volunteer wheat. Populations can build up to extremely high levels and that can serve as a point source for infestation of the new wheat that is being planted this month and into September.

“When this happens, you end up getting an early fall infection of wheat streak, which is devastating to the wheat crop,” Rush said. “Neither the mite nor the disease can be treated, so the producer can’t fix the situation once it occurs.”

This infection can be minimized or even avoided if producers will go out in a timely manner and get rid of any volunteer wheat, he said. It will also help to plant as late as possible.

“So many people did not do that last year, and that was one of the things that set up the disastrous wheat year last year,” Rush said.

He said he has data to show that in spite of the drought, dryland fields planted later that were not infected by wheat streak did well.

“Everybody had drought, but the fields infected by wheat streak were much, much worse at harvest time,” he said. “Even some irrigated producers had significant losses because of it and the combination of other diseases.”

“We know there is not much you can do about CRP (Conservation Reserve Program) grasses, but there is something to do about the volunteer wheat,” he said. “If you have a strip of volunteer wheat in the ditch around your field, I would get rid of it there too.”

Rush said it was so dry for so long, from harvest up until July, and many acres of wheat were abandoned. Then the rains came and a lot of that grain that didn’t get harvested will start coming up.

Also, he said, the concern is that dryland farmers will start planting as soon as possible to take advantage of the moisture. So there will be no disconnect between the volunteer wheat (wheat seed sprouting from previous years) and the new emerging crop, and that sets up the infection situation.

Dr. Brent Bean, Texas AgriLife Extension Service agronomist, said although there are a few varieties with some resistance to wheat streak mosaic that producers could plant, none of the varieties are immune from the disease. It is critical producers do what they can to reduce those populations of that over-summering host, Bean said.

“Once you are infected in the early fall and the virus gets a chance to get established, the virus is not going to go away and will likely only get worse,” Rush said.

Bean said the weather conditions later on will play a large role of how severe the infection is and how widespread it becomes in a given field.

“Any inputs to fall-infected wheat need to be carefully considered once you know you have an infection,” he said.

Rush said a producer irrigating wheat at 50 percent to 100 percent of the evapotranspiration rate could lose up $350 to $450 per acre (including inputs) if the crop ends up becoming infected early with wheat streak.

Dr. Ron French, AgriLife Extension plant pathologist in Amarillo, and Bean have given numerous talks at wheat field days, grower meetings, AgriLife Extension agent trainings, agricultural industry talks and other speaking events about this subject.

“You can’t remind producers too many times how important this simple wheat disease management practice can be to their bottom line,” French said.

“Although volunteer wheat is the most favorable host for the wheat curl mite, we cannot rule out barley, corn, triticale, rye and other grasses or grassy weeds,” he said. “These crops also can potentially serve as a ‘green bridge’ for the wheat curl mite to survive from one season to another.”

Volunteer wheat and grass weeds should be taken care of at least 21 days prior to planting by using tillage, a burn-down herbicide, minimum tillage or mowing, French said.

“Current insecticide treatments do not effectively manage the mites,” he said. “Therefore, destroying the host plants for the wheat curl mite is the action to take until plant breeders can come up with good resistant varieties against these viruses.”

The other options are to delay plantings, especially if wheat fields are close to Conservation Reserve Program fields, or plant after the first frost, French said.

The much-needed moisture received provides the setup for a really good wheat season, Rush said.

“It would be a shame to let this good start turn into a disaster because farmers failed to take care of something they could easily control,” he said.

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