Laricobius nigrinus Fender, native to the Pacific Northwest, is being evaluated as a potential biological control agent of the hemlock woolly adelgid, Adelges tsugae Annand, in the eastern United States. Members of the genus Laricobius feed exclusively on adelgids. Adelges tsugae is found on hemlocks (Tsuga sp.) in North America and Asia, but is considered only a pest of eastern [Tsuga canadensis (L.) Carrière] and Carolina (Tsuga caroliniana Engelmann) hemlocks in eastern North America. This is the first detailed study of the life history of L. nigrinus and its interaction with A. tsugae. Results of a 2-year field study conducted in a seed orchard in British Columbia on the seasonal abundance of L. nigrinus and its prey, A. tsugae, revealed that (i) the sistens generation of A. tsugae matures 2-3 months earlier than previously reported in Virginia and Connecticut, (ii) no A. tsugae sexuparae were observed, which differs from findings in Virginia and Connecticut, (iii) L. nigrinus adults undergo an aestival diapause that coincides with diapausing first instar A. tsugae sistens, and (iv) oviposition and subsequent larval development of L. nigrinus coincides with oviposition by the A. tsugae sistens adults, indicating good synchrony between L. nigrinus and suitable prey stages of A. tsugae.

No abstract

Laricobius nigrinus Fender is a specialist predator of the hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), a lethal pest of hemlock (Tsuga spp.) in the eastern United States. A release was conducted in 2003 in Virginia to evaluate survival and oviposition of L. nigrinus adults, egg development in the field, and their impact on HWA density. In March, April, and May, groups of zero, one, two, or three L. nigrinus females were caged on 64 hemlock branches. After 10 days, half the branches were removed to determine L. nigrinus adult survival, total eggs laid, and oviposition location with respect to prey abundance. Beetles on branches remaining in the field were recovered and recaged on new branches every 10 days. The estimated 10 344 eggs laid on branches left in the field represent the first field release of L. nigrinus in the eastern United States. The density of L. nigrinus adults affected the total eggs laid per female and oviposition site selection. Branches caged with L. nigrinus had lower densities of HWA than branches without predators. Although F1 adults were not recovered from this release site in fall 2003, F2 adults were recovered in fall 2004. Laricobius nigrinus shows promise as a biological control agent for HWA in the eastern United States.

Laricobius nigrinus Fender is being reared for release as a biological control agent for hemlock woolly adelgid (HWA), Adelges tsugae Annand. HWA is an introduced insect lethal to hemlock trees (Tsuga canadensis (L.) Carr. and T. caroliniana Engelm.) in the eastern United States. In nature, the predator (Laricobius nigrinus) and its prey (HWA) undergo a dormant period in the summer (aestivation). In the laboratory, the aestivation of L. nigrinus has not been synchronized with that of HWA, resulting in significant predator mortality. Four factors (genetics, temperature, photoperiod, and moisture) were investigated for their effects on aestivation in L. nigrinus. Both the number of individuals and the time at which they emerged from aestivation were measured in response to these factors. Temperature was the most important cue for termination of aestivation, and photoperiod was a modifying factor. High temperature and long day length delayed emergence and high moisture levels resulted in greater emergence but did not affect emergence time. Genetics, as represented by broods, was not a major factor in aestivation termination. These results have led to improvement in rearing L. nigrinus, since emergence from aestivation can now be synchronized with the active period of HWA. Increased success in rearing has expedited field releases of L. nigrinus in the eastern United States.

No abstract