
Bt Sweet Corn Sours Hungry CaterpillarsBy Jan Suszkiw April
2, 1998Crop-hungry caterpillars could be in for a fatal case of indigestion. That's the latest word from a team of scientists from Novartis Seeds, Inc., and
USDA's Agricultural Research Service in
Tifton, Georgia. They are evaluating new hybrid lines of sweet corn Novartis
bioengineered to produce a toxin from the bacterium Bacillus thuringiensis. The Bt hybrids carry a gene Novartis licensed from Monsanto Co. under the
Yield Gard trademark. After they've been approved by the EPA, these hybrids
could help reduce chemical insecticide applications. In Florida, which produces
much of the nation's fresh market corn, farmers must often spray up to 40 times
a season to ensure unblemished, worm-free ears. This spraying can endanger
beneficial insects and the environment. In the genetically enhanced sweet corn, the Bt toxin would be produced
throughout the plant where caterpillars feed. Bt toxins don't harm humans,
livestock, beneficial insects or other animals. But in corn earworm and fall
armyworms, the toxin ruptures the caterpillar pests' gut tissues. The result:
They either stop feeding or die. That's what ARS entomologists Bill Wiseman and Robert Lynch observed during
feeding trials. In one experiment, they placed 3-day-old hatchling worms on a
diet of silks from four different Bt corn lines. They then monitored their
growth and feeding behavior--and subsequent death. After about a week, 100
percent of the worms had died. Larger, six-day-old worms placed on the same
diet didn't fare much better; only 10 percent survived after 10 days. In field plots, Wiseman and colleagues saw less kernel feeding damage per
square centimeter on Bt corn ears than on several resistant or susceptible check
varieties. More studies are planned to see if "spot" insecticide use
will mean even less kernel damage. Scientific contacts: Robert Lynch, Bill Wiseman,
Insect Biology and Population
Management Research Laboratory, Tifton, Georgia, phone (912) 387-2375, fax
(912) 387-2321, [email protected] Story contacts Jan R Suszkiw U.S. Department of Agriculture | |