Interactions between the parasitoid Rhopus nigroclavatus (Ashmead) (Hymenoptera : Encyrtidae) and its mealybug hosts Tridiscus sporoboli (Cockerell) and Trionymus sp (Homoptera : Pseudococcidae)

This research investigated age-class-specific parasitism rates of the buffa lograss mealybugs Tridiscus sporoboli (Cockerell) and Trionymus sp. by Rhop us nigroclavatus (Ashmead) (Hymenoptera; Encyrtidae), size class preference of this parasitoid, and mealybug-parasitoid interactions through choice an d no-choice studies. In the no-choice studies, the mean rates of parasitism by R. nigroclavatus were 45, 20, 0, and 0%, respectively, for mealybugs ad ult female, third and fourth instars, first and second instars, and eggs. C hoice studies indicated that rate of parasitism increased with host size. T he mean rates of parasitism on mealybugs in the choice studies were 100% fo r adult females, 24% for third and fourth instars, 0% for first and second instars, and 0% for eggs. A second set of choice studies investigating meal ybug/parasitoid behavior revealed that R. nigroclavatus oviposits in all po st-egg mealybug age classes, but first and second instars were less often p arasitized than older mealybugs. (C) 2001 Academic Press.