Comparison between a native and exotic adelgid as hosts for Laricobius rubidus (Coleoptera: Derodontidae)

Laricobius rubidus LeConte, native to eastern North America whose primary host is Pineus strobi Hartig, has been observed in association with Adelges tsugae, an exotic and lethal pest of hemlock trees in eastern North America. Pineus strobi and A. tsugae were used to evaluate host preference and suitability of this predatory beetle to determine in part its suitability as a potential biological control agent of A. tsugae. In a paired-choice oviposition test, L. rubidus preferred to oviposit in P strobi ovisacs over those of A. tsugae. However, in the no-choice oviposition test, there was no significant difference in the mean number of eggs laid by L. rubidus females in P strobi or A. tsugae ovisacs. There were no significant differences in larval developmental time or survivorship for L. rubidus reared on a diet of either P strobi or A. tsugae. Laricobius rubidus completed development to the adult stage on A. tsugae indicating that it is a suitable host and therefore has the potential to contribute to biological control of A. tsugae in the eastern United States. The introduction of a congener, Laricobius nigrinus to eastern North America may result in competition with L. rubidus on A. tsugae, but the inability of L. nigrinus to complete development on P strobi suggests that the two congeners will not compete on the primary host of L. rubidus.