Spying on Corn Rootworm Predators Nightlife
By Don Comis
October 30, 2009
Agricultural Research Service (ARS)
G. Lundgren, while exploring corn fields at night, has found a very
different group of predators than the ones that feed during the day. It turns
out that these night-time predators have a great appetite for corn rootworms,
the most costly pest of corn in the world.
Research on day-active and night-active predatory insects is important for
scientists who are developing strategies that maximize the potential of the
natural predators in crop pest control.
During his night studies, Lundgren focuses on the top few inches of the soil
surface, where rootworm larvae do most of their damage to corn roots. Lundgren
works at the ARS
Central Agricultural Research Laboratory in Brookings, S.D.
Hes found that during the night, there is abundant and diverse life
underground, with predators including ground beetles, rove beetles, spiders,
crickets, and daddy-longlegs.
Wondering how so many and such diverse species could manage in the confines
of the upper surface of soil near corn roots, Lundgren's research revealed the
answer might be separation by time, with some insects confining their activity
to as little as a three-hour window.
The scientists have two ways to spy on predators. One is to place pinned
rootworms as sentinels. The researchers come back later with a red light to see
which rootworms have been attacked and which predators are hanging around.
Insects cant see red light. The second way is to collect predators in a
timed trap. Trapped predators are analyzed for corn rootworm DNA. This gives
researchers information about how long the predators are hunting and the amount
of rootworms the predators eat.
Lundgren found that one common carabid beetle, Poecilus chalcites,
prefers day work, while another common carabid, Cyclotrachelus
alternans, works a night shift, from 10 p.m. to 3 a.m. Wolf spiders search
for rootworms during the night, while some other spiders hunt during the day.
This work supports the U.S. Department of
Agricultures research priority of ensuring international food
security. ARS is the principal intramural scientific research agency of USDA.