When corn earworms are infected with naturally-occurring baculoviruses they may not die right away, instead continuing to chew on plants. One baculovirus has been genetically altered to overwhelm the earworm with an overdose of an appetite-stopping hormone. The hormone, called helicokinin-II, is produced in the earworm to help regulate physiological processes, enabling the insect to grow from caterpillar to adult moth.
The gene responsible for making the hormone was cloned and inserted into the baculovirus. Once ingested, the virus quickly replicates inside the earworm's gut cells. In the process additional helicokinin-II is produced, adding to any already present. The extra hormone induces the insect to stop eating and excrete most of its water.
In lab experiments newly hatched corn earworms infected with the virus typically stopped eating after about 48 hours. By 20 days, only 3% had survived and pupated, compared to 100% of the virus-free worms. The next step is testing the altered baculovirus against wild corn earworms in the field.
The hormone can't just be sprayed directly on plants to stop earworms from eating because the insects wouldn't get enough into the gut to be effective and the protein would degrade too quickly. The baculovirus is an ideal delivery mechanism since it can get inside the earworm and manufacture the hormone. Since the technology for growing baculoviruses in special industrial vats already exists, this could expedite the development of this virus as a product growers could spray onto crops. It is expected that the technology will be ready to be passed on to a commercial company for field studies in about a year.
Suszkiw, J. 1998. Altered baculovirus dooms corn earworms. Agricultural Research/March 1998, pp. 25-26.
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