Laricobius Beetles

Laricobius nigrinus & Laricobius osakensis

Laricobius nigrinus
is a beetle species from the Pacific Northwest, where there is a widespread native population of HWA. In this range, La. nigrinus is one of the most abundant predators of HWA, helping to suppress HWA populations so that western hemlock species are not stressed by the infestations. We have released this species at 19 sites in New York since 2009.

L. osakensis is a beetle species from southern Japan, where the population of HWA found in Eastern North America originated. Since La. osakensis is specialized to feed upon the biotype of HWA found in eastern North America, it offers a promising biocontrol option for managing HWA. While we are studying and rearing this species in the lab, we have not released La. osakensis in New York.

Laricobius as Biocontrol

Laricobius, or “Little Lari”, is one of the most common predators of HWA in HWA’s native range, and its life cycle synchronizes with that of HWA. By feeding throughout the fall, winter, and spring, and becoming dormant in the summer, Lari’s life cycle can match up with the life cycle of HWA. Adult beetles feed during the fall and winter and lay their eggs in the early spring. In the spring, the beetle larvae feed upon HWA eggs and early instar nymphs before dropping into the soil to pupate and mature.

Laricobius in New York

Laricobius beetles were first released in the United States in 2003. Since that time, they have been released in 16 states and there have been many sites with signs of establishment. The first Laricobius releases in New York took place in 2008 with establishment confirmed at three of those release sites. The New York State Hemlock Initiative continues to maintain a L. nigrinus lab colony for releases in autumn.

Laricobius beetles feed on the sistens generation of HWA, which is the first of HWA’s two annual generations. Throughout the fall season, adult beetles feed on developing and adult HWA. Beetles lay their eggs around the time HWA adults are laying eggs. When beetle eggs hatch, the larvae fall into the soil where they pupate to emerge the next year in the fall.

Getting Involved with Laricobius Projects

There are several ways to help maintain our colony and expand our lab’s capacity. Find out how you can help:

Food collection sites
One of the challenges that we face is providing our lab colonies with enough food to reproduce successfully in the lab. Landowners can help us by providing infested hemlock foliage for beetles to feed on throughout the fall and winter seasons. Landowners with ample infested hemlock foliage on their property are encouraged to get in touch with us. You can get involved by emailing

Hemlock Hedges
If you have a hemlock hedge, you can help us by making your hedge a biocontrol bug insectary. Hemlock hedges help us to raise a small population of Laricobius beetles adapted to the local climate for nearby releases. To learn more about our hemlock hedge program, you can visit our Hemlock Hedge page.

HWA Phenology
In order to accurately time our biocontrol releases, we rely on citizen scientists around the state to monitor local HWA populations for transitions between major life stages. For Laricobius beetles, this means watching for HWA to wake from its summer dormant period and begin feeding. You can learn more about the timing of HWA’s major life cycles and why it is so critical for our biocontrol program on our HWA Phenology page.