The effect of host density and parasitoid inoculum size on the mass production of Leptomastix dactylopii Howard (Hymenoptera: Encyrtidae) and Aphytis lingnanensis Compere (Hymenoptera: Aphelinidae) in Queensland.
Leptomastix dactylopii and Aphytis lingnanensis are mass reared for augmentative release in Queensland citrus in the spring-early summer against citrus mealybug, Planococcus citri, and red scale, Aonidiella aurantii, respectively. This paper reports the results of studies on the effects of host density and inoculum size on parasitoid production in a system using P. citri as host for L. dactylopii, and oleander scale, Aspidiotus nerii, for Aphytis lingnanensis, with both hosts reared on butternut pumpkins, Cucurbita moschata. For L. dactylopii, highest production was achieved when mealybugs (21 days old at 25°C) were exposed to a parasitoid inoculum of 3 per cm2. A host density of 20 per cm2 (6000 per pumpkin) was most efficient because it resulted in higher levels of parasitism, produced numbers of parasitoids only slightly less than the higher density, and suffered lower losses due to rotting pumpkins. A. lingnanensis production was highest when the density of oleander scale was 60 per cm2 and the parasitoid inoculum 33 per cm2.