none Laboratory tests with the acaricide Plictran (tricyclohexylhydroxystannane), suggest that this gypsy moth feeding deterrent, like B. thuringiensis, has minimal direct effects on larval survival, adult longevity and progeny production of the parasite, C. melanoscelus. Plictran and very low doses of B. thuringiensis (down to 1/25 the recommended dose) sprayed on apple trees did not significantly reduce gypsy moth numbers but did retard caterpillar development. Thus, these materials should increase parasitization by C. melanoscelus in the field because they increase the length of time the parasite, which attacks only small hosts successfully, can parasitize caterpillars.