Natural Enzyme Deters Fall Armyworms and Other
By Jan Suszkiw
February 22, 2007
Furnishing corn plants with genes
for producing the enzyme ß-N-acetyl hexosaminidase (NAHA) may offer a way to
fend off mold-spreading caterpillars and beetles, Agricultural Research Service
(ARS) studies suggest.
After hatching from eggs, fall armyworm caterpillars feed on corn plant
leaves before advancing on the ears, where succulent kernels await. Other
caterpillars and beetle pests feed there, too. When husks are chewed open,
kernels can become exposed to mycotoxin-producing fungi. Insecticide spraying
within label recommendations helps prevent such feeding and contamination. But
the practice can be costly to use and harmful to beneficial insects.
As a possible alternative, ARS scientists
Pinkerton are testing modified strains of corn that produce NAHA throughout
the crop plant's tissues. In laboratory trials at the ARS National Center for
Agricultural Utilization Research in Peoria, Ill., 100 percent of newly hatched
fall armyworms that ingested NAHA-containing leaf tissue from some of the
modified corn plants being studied died within three days.
The degree to which the caterpillars stopped feeding on all of the modified
corn plants depended on how much NAHA the plants actually produced, the
scientists observed. Corn earworm caterpillars, another pest they tested, were
also adversely affected by NAHA-containing plants.
The team's examination of NAHA and other enzymes like it is part of a
broader effort at the ARS center to develop novel ways of shielding corn from
mycotoxin contamination, which costs farmers and processors millions of dollars
annually in losses. Of particular interest is determining effective
combinations of corn-derived genes that confer insect-resistance levels equal
to those in corn containing the biopesticide Bacillus thuringiensis
(Bt), but that act against a wider range of pests.
Before studying NAHA-modified corn plants, the scientists used a purified
form of the enzyme derived from jack beans, Canavalia ensiformis. They
consider NAHA a promising defense for corn because it occurs in foods eaten by
humans, such as cabbage and apple, and it targets chitin, a key component of
insects but not of humans or other animals.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.