The invasive, exotic multicolored Asian lady beetle, Harmonia axyridis Pallas, is an effective predator of numerous homopteran pest species. A paucity of literature exists on the potential non-target effects of H. axyridis. Unpublished data have indicated that H. axyridis will consume both eggs and first instar Danaus plexippus (L.) under laboratory and field conditions when no other food is available. However, in the field, common milkweed, Asclepias syriaca L., is often infested with oleander aphid, Aphis nerii Boyer de Fonscolombe, as well as D. plexippus. In the present studies, we examine the effect of aphids on the predation of immature D. plexippus by H. axyridis. Large field cages were used to examine the effect of various densities of H. axyrids larvae and the effect of aphids being included as another food source for the predators. Preliminary data indicate significant reductions of D. plexippus survival with increasing per plant density of H. axyridis, and that survival of D. plexippus is not dependent upon the presence or absence of aphids. An open field survivorship study was conducted to compare the survival of D. plexippus on potted A. syriaca plants with aphids, to that of plants without aphids when plants are exposed to the natural guild of generalist predators, including H. axyridis. Application of these results will be discussed in the context of an ecological risk assessment of the non-target effects of H. axyridis on D. plexippus.
Species 1: Lepidoptera Danaidae Danaus plexippus (monarch butterfly)
Species 2: Coleoptera Coccinellidae Harmonia axyridis (multicolored Asian lady beetle)
Species 3: Homoptera Aphididae Aphis nerii (oleander aphid, milkweed aphid)
Keywords: predation, non-target species
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