Virus To Wage Hormonal Sabotage on Corn Earworms

By Jan Suszkiw
March 12, 1998

With high-tech help, a natural insect virus could deprive corn earworms of their greatest pleasure: feasting on corn plants at farmers' expense.

The virus--called a baculovirus--infects corn earworms to multiply and spread. But it is slow to kill, and may not adequately protect the plants. Now a more potent form of the virus has been developed by Agricultural Research Service scientist Ashok Raina. Using biotechnology, he equipped the virus with new genes for making a natural hormone to stem the corn earworm's appetite.

Raina discovered the hormone, helicokinin-II (Hez-HK-II), in earlier studies of the corn earworm's nervous system. He then cloned the Hez-HK-II gene and inserted it into the virus.

Normally, the hormone helps regulate the insect's growth from caterpillar to adult moth. But Raina showed that infecting the pest with the modified virus leads to hormonal sabotage. That's because the virus makes a surplus of Hez-HK-II after invading the worm's gut cells.

This overload stops the pest from feeding--a potential boon for the corn plant's leaves, silk, tassel and other parts. In the South, the pest costs farmers nearly $2 billion annually in losses and chemical control expenses.

The baculovirus is an appealing alternative: It kills the pest from within, eventually degrades outside its host and doesn't harm humans, animals, plants or beneficial insects. In lab studies, hatchling worms infected with the modified virus typically stopped eating after 48 hours. By 20 days, only 3 percent survived and pupated compared with 100 percent for virus-free worms.

The true test will come with field studies against wild corn earworms, which are expected to be more robust than lab-reared specimens used thus far. Raina is now collaborating with a commercial company to explore the virus' potential as a biopesticide.

A more detailed story appears in the March issue of ARS' monthly magazine,Agricultural Research. The story is also on the World Wide Web at:

/is/AR/archive/mar98/corn0398.htm

Scientific contact: Ashok Raina, Insect Biocontrol Laboratory, Beltsville, MD 20705, phone (301) 504-9296, fax (301) 504-8190, araina@asrr.arsusda.gov.