Eye Out for the Corn Farmer's Best Friend
By Don Comis
January 17, 2003
Ground beetles may not be welcome to
city folk who mistake them for small cockroaches, but they are more than
welcome in cornfields because they can be voracious predators of the corn
farmer's worst pest, the corn rootworm.
Corn rootworms eating away at corn roots cause farmers to spray more
insecticide than do any other pest in the United States.
Ground beetles are so important that Agricultural Research Service scientists
are monitoring their populations to ensure that new pesticides--including
natural insecticides produced by new varieties of corn plants--don't harm them.
As part of this effort, ARS scientists have designed a new, revolving trap that
operates like a clock.
ARS entomologist Mike Ellsbury created the new trap by modifying a mosquito
trap that hangs from a tree. The clockwork trap rotates so it catches the
beetles in one of eight bottles every three hours, allowing Ellsbury to learn
what species are active when. Ellsbury attached the rotating trap mechanism to
a plastic disc, then covered the disc with soil and plant litter, completely
disguising it, leaving only a single pitfall opening exposed.
There are more than 20,000 species of ground beetles in the family
Carabidae. Knowing when different species are active offers diet clues that can
be helpful in protecting ground beetles and in learning how their numbers can
be maintained or even increased.
Ellsbury has three of the new traps and plans to build more. He also has 105
conventional single pitfall traps and has placed the traps in experimental
plots of corn. By keeping track of the location, numbers and species of ground
beetles, Ellsbury and colleagues will learn whether the new corn varieties have
any harmful effects on the beetles.
With corn rootworm evolving ways around the crop rotations traditionally
used to control it, ground beetles are increasingly becoming a corn farmer's
ARS is the U.S. Department of
Agriculture's chief scientific research agency.