Discovery At Colorado State University May Help To Develop Environmentally-Friendly Pesticide
Thursday, January 15, 1998
FORT COLLINS--A Colorado State University scientist's
discovery may lead to a safer and cheaper way to prevent termites
from infesting homes, where they cause an estimated $750 million
in damage in the United States annually.
Entomologist Louis Bjostad found that termites' natural
reliance on carbon dioxide to find food and shelter also can be
used against the insects as a non-toxic alternative to current
forms of pest control.
"When we first initiated the experiments, we wondered if the
concept would be too simple to work," Bjostad said. "Our findings
show that carbon dioxide undoubtedly attracts termites, which
opens up a whole range of possibilities for controlling these
pests."
Bjostad, with researchers Elisa Bernklau and Erich Fromm,
made the discovery by placing two species of termites--
Reticulitermes tibialis, a species common to Colorado, and R.
flavipes, a frequent pest in the Great Lakes--at one end of a T-
shaped tube. In one arm, researchers pumped in normal air, and in
the other, CO2 in concentrations higher than those found in
normal soil.
"When a termite came to the point of choosing an arm, it
moved its antennae to one side of the tube, then the other,"
Bjostad said of the experiments. "Most of them chose the side
containing the carbon dioxide."
Bjostad and his colleagues believe termites are naturally
attracted to carbon dioxide for two reasons. Rotting wood--the
termites' main source of food--releases CO2, a process that
likely guides the insects to food. Concentrations of the gas
inside termite colonies is higher than ambient air, suggesting
termites also use CO2 to find their way home.
Now Bjostad and his colleagues are using the discovery to
create a substance that slowly releases CO2 underground to lure
termites away from houses and other structures where they cause
damage. Because it occurs in abundance naturally, CO2 offers an
inexpensive, non-toxic alternative to current methods of pest
control, Bjostad said. Environmentally-friendly insecticides now
in use are designed to pass from one termite to the other, but
don't always do the job. As a result, pest controllers often
resort to other toxic chemicals to eradicate termites.
Chemical companies have expressed interest in the finding,
Bjostad said, in part because of the high costs to register new
insecticides and chemicals. In-depth efficacy and public health
studies and other research--costing an average $50 million--must
be submitted to federal agencies before a chemical company can
manufacture and sell a product. Because CO2 is a natural gas,
those costly studies would not be necessary, Bjostad points out.
Bjostad believes the CO2 discovery opens the door for a
number of uses, such as luring termites to monitoring traps or to
sources of insecticides. Slow releases of CO2 also could be
used to confuse termite behavior to the point where a colony
cannot sustain itself. The breakthrough even may have
applications in new home construction.
Bjostad's lab plans to conduct experiments with other
termite species common to the United States to determine what
range of CO2 is effective on all species. Because the basic
biology of other termite species is very similar, the Colorado
State researchers expect little difference in their reactions.
The initial termite studies were funded by the Colorado
Agricultural Experiment Station.
This latest breakthrough was prompted by other research
under way in Bjostad's lab. Last year, the Colorado State team
showed that western corn rootworm--a pest that causes $1 billion
in crop damage each year--solely uses CO2 to find young corn
roots. Larvae must locate roots within three days after hatching
or die of starvation. Bjostad developed several pellets
containing natural ingredients that slowly release the gas. The
pellets, buried at corn planting time, steer rootworm larvae off
course.
Bjostad's recent discoveries with termites and rootworm
points to the possibility that many soil-borne insects also rely
on CO2 to locate food and shelter. If so, the gas could be used
to steer other agricultural and household pests away from places
they do harm.
"Manmade insecticides assume the pests will come into
contact with the chemical and die," Bjostad said. "This is a case
where we're using the pests' own genetic predispositions to
elements that already exist in nature to change their behavior or
lure them to their deaths."
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