Ooencyrtus kuvanae(Howard) parasitism of gypsy moth,Lymantria dispar(L.), egg masses (EMs) laid on different host species and substrates was studied in newly infested areas in Virginia. Parasitization rates of gypsy moth EMs byO. kuvanaewere highest on red maple and inanimate objects and lowest on oaks. The effect of host plant species on parasitism was independent of the number of eggs per mass and may be due to the effects of bark texture on egg mass geometry and searching behavior ofO. kuvanae. Percent parasitization was also inversely related to eggs per mass; the latter is a function of host suitability and gypsy moth population density.O. kuvanaeappears to be incapable of maintaining gypsy moth populations at low densities but may be an additional factor mediating against the reproductive success of individuals feeding on nonpreferred host plant species.