By Jan Suszkiw
April 11, 1997Double trouble may loom ahead for beet
armyworms that ravage cotton plants.
Scientists with USDA’s Agricultural
Research Service are teaming a natural insect virus with a parasitic wasp
to put the kibosh on the pest.
The virus, called a nuclear polyhedrosis virus, liquefies the bodies of beet
armyworm caterpillars it infects. But it doesn’t harm people, animals or
beneficial bugs.
The parasitic wasp, Cotesia marginventris, is a native U.S. insect
that lays its eggs in the worm. Wasp larvae hatch from the eggs and feed on the
pest’s innards.
In small field plots, spraying the virus on cotton plants killed over 50
percent of the worms in 4 days. Researchers then released about 500
Cotesia wasps; they doomed half the survivors. In all, the virus-wasp
combo killed three-fourths of the beet armyworms.
Currently, growers fight the beet armyworm by spraying insecticide. But
using its natural enemies instead would spare helpful predators like big-eyed
bugs that keep other pests in check.
In the studies, researchers used--with equal success--a commercial virus
product registered as Spod-X and an ARS-developed strain. Special techniques
were used to mass-rear the wasps.
Scientific contact: P. Glynn Tillman, USDA-ARS
Biological
Control and Mass Rearing Unit, Mississippi State, Miss., phone (601)
323-2230, fax (601) 323-0478, pgt2@ra.msstate.edu.