Amarillo, Texas
March 6, 2009
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 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.” |
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