Producers looking for aphid control in wheat fields might have a new tool, according to a Texas A&M AgriLife Research study.
Dr. Jerry Michels, AgriLife Research entomologist in Amarillo, and Johnny Bible, research assistant, are conducting a study on control of small grain aphids with seed-applied thiamethoxam insecticide, or Cruiser, at the North Plains Research Field north of Dumas.
Michels and Bible have demonstrated the control for the past three years as part of the iWheat project.
iWheat is a multi-state project funded by the U.S. Department of Agriculture Risk Avoidance and Mitigation Program, also known as RAMP. The goal is to develop a region-wide pest management program for winter wheat that includes insects, plant diseases, weeds and agronomic practices.
The iWheat team includes members from AgriLife Research, Texas A&M AgriLife Extension Service, Colorado State University, Kansas State University, Oklahoma State University, University of Nebraska and USDA-Agricultural Research Service.
“The team laid the foundation for iWheat in 2010,” Michels said. “Some of our efforts have been hampered by the current drought, and of course this year’s severe late freezes. But, we made the best of the opportunities we’ve had, and implementation of iWheat is underway.
“There are some additional features we want to incorporate into iWheat that need user input,” he said. “The most important features that will make iWheat shine are maps and predictive models. We need to accumulate data this year and in the years to come. The more data we have on pests, varieties, yield and other production components, the more accurate our predictive models will be, and in real time you can access information on problems throughout the season. Michels said anyone can join iWheat by going to http://my.iwheat.org to register at no cost.
Once completed, the results of the seed-applied thiamethoxam insecticide study will be part of the iWheat database, he said.
“Because of drought and unusually high temperatures, the greenbugs, Russian wheat aphids and birdcherry oat aphids were found only in low densities in 2011-12,” Michels said. “This year, however, cooler temperatures and a little more moisture resulted in a natural aphid infestation in our plots and a successful demonstration.”
The plot consisted of level borders planted to either Hatcher or TAM 110 wheat varieties. The plots were sampled five times this spring, beginning in early April. Data consisted of aphids-per-tiller and percentage of infested tillers.
Ten late-season freezes occurring between April 4 and May 5 almost certainly affected aphid infestations and damaged the wheat, Michels said. However, on most sampling dates, there was a clear indication that the treated plots had lower aphid infestation than untreated plots.
“We had significant populations,” he said. “The untreated, by April, had up to 85 percent infestations of primarily greenbugs, although we did have some Russian wheat aphid and some birdcherry oat aphid. Where we were getting upwards of 80 percent infested tillers on untreated, we were down below 15 percent to 16 percent of the infested tillers in the treated plots in early April.”
With the exception of the April 18 and May 15 sampling dates, Hatcher wheat treated with thiamethoxam had significantly fewer infested tillers than the untreated counterpart. Treated TAM 110 wheat had significantly fewer infested tillers than the untreated plots on April 4, but was irregular after that date, and no additional sampling dates showed significant differences in tiller infestation.
Michels said the tiller samples followed the Glance ‘N Go scouting system protocol to determine if an aphid infestation warranted an additional treatment. At one sampling date, April 4, the protocol indicated that a foliar insecticide application would be economically valuable. This was based on a treatment cost of $11.42 per acre and wheat priced at $6.90 per bushel.
However, subsequent freezes seemed to have an impact on the aphids, he said. By the May 15 sample, there were few aphids or infested tillers because lady beetles and parasitic wasps had practically eliminated the aphid infestations.
“Our conclusion is that, although freezes caused problems, the treatment with Cruiser will last about seven months and give you pretty good aphid control,” Michels said. “If you use the Glance ‘N Go method to look at infested tillers and make a management decision as to when you are going to apply a foliar application, our readings late in April were indicating those untreated plots were ready to be sprayed. We are really excited Cruiser is working.”
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