Effect of methamidophos residue on the pentatomid egg parasitoids Trissolcus basalis and T-utahensis (Hymenoptera: Scelionidae)

Effects of methamidophos residue on adults and immatures of the pentatomid egg parasitoids Trissolcus basalis (Wollaston) and T. utahensis (Ashmead) were assessed in the field and laboratory. Survival of adult females of both species exposed to field-treated tomato foliage was significantly reduced (ca. 50%) in the presence of 2- and 4-day old residues. Residues of as much as 16 days significantly reduced survival in T. basalis but not in T. utahensis. Emergence of T. basalis from egg masses of Nezara viridula (L.) exposed to the same field treatment was not significantly reduced, but survival of emergent adults was significantly reduced. Adult emergence of either T. basalis or T. utahensis from eggs of Euschistus conspersus Uhler and treated as pupae was not significantly affected, but survival of emergent females and males was significantly reduced for both species. When the parasitoids were treated as larvae, emergence rate was significantly reduced for T. basalis but not for T. utahensis, and survival of emergent males and females was significantly reduced for both species. Reproductive capacity of emergent females was not significantly reduced in either species, but sex ratio of the progeny was male-biased for each species. Because postemergence survival of adults was greatly reduced by methamidophos treatment, percentage emergence of parasitoids from treated eggs is not an adequate measure of ecological selectivity of this insecticide. (C) 1996 Academic Press, Inc.