Rootworms Pose First Challenge to Decades-Old Pest Control Strategy
By Don Comis
February 28, 2002
For the first time, corn
rootworms--the most damaging pest of corn in the United States--recently
changed their behavior and foiled crop rotation strategies long counted on to
break their destructive cycle.
Now Agricultural Research Service
scientists hope a soon-to-be-completed 5-year cooperative research agreement
with Monsanto Company, St. Louis, Mo.,
will help them regain the upper hand against the pest. In the study, the
scientists are using a 2-in-1 cornfield strategy--a mix of transgenic and
nontransgenic corn plants--against the rootworms. The transgenic plants have
been genetically engineered to produce Bacillus thuriengensis
For many years, farmers could confidently reduce rootworm numbers by
switching their cornfields to soybeans every other year, planting corn
elsewhere on their farms. The rootworms would starve to death after hatching in
a soybean field the next spring.
But, in recent years, farmers noticed that adult western corn rootworm
beetles were flying out of the cornfields to lay eggs in soybean fields that
would become cornfields the next spring when their hungry worm offspring
hatched in the soil.
To make matters worse, more eggs of their northern brethren started taking
two years to hatch, timing their offspring perfectly for a 2-year,
corn-soybean-corn rotation. And western rootworms have developed resistance to
insecticides applied in fields planted to corn every year.
To counter the pests ability to adapt to various control tactics, ARS
scientists are studying the resistant-insect management strategy of
interplanting regular corn plants among transgenic corn plants.
The idea is to delay possible development of resistance by giving any adults
that fed on the transgenic corn plants--and survived--the opportunity to mate
with other, non-Bt-challenged beetles, which fed on regular corn.
ARS is the U.S. Department of
Agricultures chief scientific research agency.