Beaumont, Texas, USA
August 12, 2009
See no weevil: researcher tracks
rice bugs to help farmers, consumers
When there’s something bugging rice farmers, a large segment of
the world’s population is likely to find out.
Americans eat about 20.5 pounds of rice a year, while globally
people annually eat about 126 pounds each, according to the
United Nations Food and Agriculture Organization. Yet a big bite
is also taken by insects in the field every year.
One of the worst, the rice water weevil, is a Southeast Texas
native measuring in at less than one-fourth inch long. But its
gray snout has chomped through much of the world making a
sizable dent in the size and quality of global rice supplies.
A Texas researcher is making great strides - many of them
splashing through rice paddies to scour grassy pinnacles and
seed heads with his net - in controlling the rice-craving
insect.
“I’m looking for ways to integrate a variety of treatments to
manage pests efficiently and economically,” said Dr. Michael
"Mo" Way, Texas
AgriLife Research entomologist at Beaumont, who has been
working with rice and soybeans there since 1982.
Rice water weevils are among the most serious pests in terms of
causing lower yields and grain quality, Way said. And they don’t
just stop in Texas. Rice water weevils have become a global pest
-- making it to California by the 1950s, to Japan in the 1970s,
then China, Taiwan and more recently, Italy. In Texas, farmers
can lose from 500-1,000 pounds per acre as this weevil swims,
crawls and flies through the field, laying eggs underwater so
the larvae can grow by gnawing on rice plant roots, the
researcher explained.
Way was patient in his quest to see no weevil. He spent six
years sweeping through fields, looking for water weevil damage
to determine at what level it would make sense for a farmer to
spend money controlling the pest.
Farmers had been referring to old data, he said, though many new
rice varieties are being grown and with newer cultural methods,
and it was not known whether these changes had made a difference
on rice weevil control.
Armed with many seasons of field data from test areas grown as
much like true farm situations as possible, Way and
then-graduate student Luis Espino compared protected versus
unprotected plots with those planted on a variety of dates. The
protected plots were treated with various insecticides.
“What we found is that if farmers plant during the optimum
planting window, then they can expect the greatest yield losses
due to water weevil,” he said. “And since we don’t recommend
planting outside that optimum time, it behooves them to control
for the weevil.
“Usually, our highest management level farmers plant during that
optimum time, from end of March to mid-April, and that enables
them to produce a ratoon, or second crop as well,” he added.
“So, it makes good economic sense to control for the weevil.”
To sample for water weevil in a field, Way and his team take a
4-inch by 4-inch plug that contains about three plants and the
soil around the roots.
“For every one larvae per core, yield is reduced about 1
percent,” he said. “So the economic injury levels (number of
insects it takes to cause significant loss) are very low -- much
lower than we thought.”
Control usually means an insecticide, he noted, but researchers
have also made strides in this area as well to develop products
that are not as toxic to the environment as in the past.
“One of these is a seed treatment with rynaxypyr, a chemical
that is far less toxic to mammals and wildlife than previous
compounds,” Way said. “Reports from the field this year where
this product was used are very, very encouraging.”
Way said because seed treatment is a preventive measure -- it
has to be applied to the seed before planting and well beyond
the time when larvae are found in the cores -- the researcher
recommends that farmers go on their field history with weevils.
“Certain areas are more prone to water weevil damage,” he said.
Farmers should also make the decision to use seed treatment
based on planting date, variety, seeding rate, typical plant
stand and time of flood. “Based on these parameters, they can
decide for themselves whether they will need the seed
treatment," he added.
The study also noted a couple of secondary benefits from the
seed treatment -- all of the chemical stays with the seed rather
than drifts in the air, and it has shown ability to control
other rice pests such as stalk borers, fall armyworm and South
American rice miner.
“So this reduces the pesticide load in the environment,” he
said. “And farmers have another tool in their toolbox.”
And people have more rice on their plates.
The multi-year study was funded mostly by the Texas Rice
Research Foundation using checkoff dollars, a percent of the
price paid at harvest, from farmers. |
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