Natural enemies of adelgids in North America: Their prospect for biological control of Adelges tsugae (Homoptera: Adelgidae)

Abstract

On eastern hemlock, we found two resident beetles preying on Adelges tsugae Annand. One is a coccinellid native to Europe, Scymnus suturalis Thunberg, that also feeds on Pineus sp. that attack pines. The other is a native derodontid beetle, Laricobius rubidus LeConte. The seasonal life history of these two species indicates that their effect on A. tsugae will be more complementary than competitive. The effectiveness of these species may be enhanced by the presence of alternative prey that attack other conifers. Among the many species imported for control of the balsam woolly adelgid, the coccinellid Aphidecta obliterata (L.) appears to have the best potential for biological control of A. tsugae. It is important to assess the incumbent population of natural enemies before introducing biological controls, in order to better understand the kind of biological controls that are most suitable and reduce displacement of native species. A multispecies strategy seems the best approach to achieve biological control of A. tsugae.