Wheat aphid infestations on the rise
AgriLife Extension entomologist advises producers to check their field
Wheat aphids are beginning to present themselves in the South Plains and Panhandle at levels that warrant treatment, a Texas AgriLife Extension Service specialist said.
Dr. Ed Bynum, AgriLife Extension entomologist in Amarillo, said infestations of greenbugs and Russian wheat aphids started showing up about two weeks ago.
While infestations typically occur at this time of year, Bynum said, the Russian wheat aphids "seem to be heavier and more widespread than we've seen in quite some time."
The first appearance of the Russian wheat aphid in the U.S. was in March 1986 in the Texas High Plains, Bynum said. The past few years they have not been a major problem, but the extreme drought conditions may have contributed to their increase this year.
Bynum said economic thresholds for treatment of both insects based upon the cost of control and the market value of wheat have been established. The document, "Managing Insect and Mite Pests of Texas Small Grains," can be used to determine if infestations warrant treatment. This guide can be found at http://amarillo.tamu.edu/programs/entotce/insectdocumentE399.pdf.
For every 1 percent of the tillers infested, there is a 0.5 percent yield loss, he said. Bynum said producers can get an estimate of the infestation by walking across a field, randomly selecting 100 tillers, each from a different site. To prevent bias, he recommends they select tillers without looking at them.
Carefully examine each tiller and record whether the tiller is infested, he said. Consider any tiller with one or more Russian wheat aphids as infested. Determine the percent of infested tillers and use the table in the guide to decide whether treatment is justified.
For example, if the market value of the crop is projected to be $50 per acre and control costs are $9 per acre, the treatment threshold is 36 percent infested tillers, he said.
There are many chemicals labeled for use in treating both of these insects, the most commonly used chemical for control is Lorsban, Bynum said. Producers need to read and follow all labels for application guidelines.
"For the Russian wheat aphid, you need to make sure you use the maximum label rate," he said. "Also, remember that effectiveness of the application can be reduced if temperatures rise above 80 degrees. So applications need to be made during the early morning when temperatures are cooler."