The only thing worse than biting into an apple and finding a worm is finding half a worm, or so the old joke goes. Now growers have another weapon to keep worms out of their apples. After 14 years of testing, entomologist Louis A. Falcon, UC Berkeley professor emeritus, has received federal registration of codling moth granulosis virus for use on apple, pear, walnut and plum trees. It has conditional registration in California and full registration will be sought.

The codling moth granulosis virus is a naturally occurring baculovirus that makes the larva lethargic and eventually dissolves them from the inside out.

Field tests have shown that with proper application, the baculovirus could control the worms as effectively as chemical pesticides, including the commonly used pesticide azinphosmethyl. And because the baculovirus attacks only a narrow range of species, leaving other insects and spiders alone, applications did not encourage the proliferation of secondary pests such as mites, scale insects and aphids.

Falcon doesn't claim the baculovirus will supplant chemical pesticides, since it is more labor intensive to apply and monitor and more expensive. Rather, he hopes the baculovirus will help cut use of chemical pesticides. Falcon says integrating use of the baculovirus with judicious application of chemical pesticides could keep the moth at very low levels in the orchard.

Currently it is unclear who will produce the baculovirus, which is registered to the University of California and an organic grower group, Association for Sensible Pest Control, Inc. For more information, contact Howard Kaplan at (510) 672-8843 or farmvest@aol.com.