Amarillo, Texas
June 22, 2004
As certain as death and taxes,
plants will have insect problems. Dr. Carl Patrick, entomologist
with Texas Cooperative Extension based in Amarillo, has
strategies for controlling crop pests in area corn, sorghum and
cotton fields.
Right now, spider mites are causing some early problems in the
edges of corn and sorghum plots. Corn borer flight is also under
way. Thrips are present in area fields.
"Spider mites are making their presence known early this year,"
Patrick said.
Above-average temperatures and dry, windy days in May
significantly added to the current mite situation. Dryland wheat
in center-pivot corners or near corn fields quickly matured.
"This situation forced the mites, commonly found in wheat, to
rapidly seek alternate hosts, namely corn and sorghum. They
arrived earlier and in greater numbers than usual," Patrick
explained.
In many area fields, miticides have been applied to suppress the
developing infestation. But selecting the right compound is
important.
"Miticides with broad spectrum activity should not be the first
choice," the entomologist advised.
For corn growers, the western corn rootworm is another nuisance
that is already out in various sizes. Patrick scouts fields
across the region and uses the corn rootworm developmental model
data generated by the North Plains Potential Evapotranspiration
Network to monitor the pest's progress.
Crop rotation, at-plant insecticides, immediate treatments for
crop rescue, or rootworm-resistant corn varieties are tools that
have hopefully minimized any loss to western corn rootworm,
Patrick said.
"Beetles will soon emerge and start feeding on leaves. But the
damage is of little consequence," he said.
Controlling beetles in refuge areas near fields where
rootworm-resistant corn grows also helps reduce next year's
populations. Patrick advises farmers who decide to use
insecticides in such spaces to apply treatments at the same time
and manner used for rootworm-resistant acres.
Growers also are seeing southwestern and European corn borer
moths active at this time. The moths are laying eggs that
produce the first generation of borers. Reports from the South
Plains show second and third phase larvae feeding in plant
whorls.
The good news is that first-generation corn borers seldom reach
economic infestation levels justifying an insecticide
application. Little or no damage from these borers is expected
on Bt corn.
But spider mites aren't satisfied with one crop host.
"Right now, the mites are showing up in sorghum, particularly
seed-production sorghum for the same reasons they hit corn," he
said.
A limited miticide arsenal for sorghum and sensitivity of
certain sorghum lines to miticides make management decisions
difficult, Patrick said. Propargite seems to be the compound of
choice. However, the mitecide may damage the plant if too much
of it becomes concentrated in the stalk area, which can happen
after a rain or irrigation, for example.
At some level, thrips are also infesting all area crops.
However, the biggest concern is their build-up in cotton,
Patrick said. The crop is thriving in warm temperatures, but
thrips can still cause a problem.
"Thrips often go for the small folded leaves in the growing end
of the plant. The pest can be overlooked, if plants aren't
closely inspected," Patrick said.
The numbers of thrips per plant, used as treatment indicators,
increases as the plant adds more leaves. Control may be
justified when the thrips equal the number of true leaves
present at the time of inspection, particularly if immature
thrips are present. Insecticide application is rarely warranted
once plants reach the five to seven true-leaf stage.
Panhandle producers count on Patrick's seasonal pest reports to
make key management decisions. The information is widely used by
Panhandle Extension agents and area specialists, in addition to
certified crop advisers.
A full complement of small grains and cotton production
information, including insect problem issues, is available on
the Internet at:
http://txipmnet.tamu.edu/crops. |