Biocontrol and Hemlock Woolly Adelgid
Biological control, or biocontrol for short, is the use of a natural predator, parasitoid, or pathogen to manage the populations of a pest species. We research predator species from HWA’s native range and release those predators in New York. At our biocontrol lab, based at Cornell University, we are currently studying two beetle species and two silver fly species for biocontrol of HWA.
Currently we release these predators on public, protected forested lands to manage local HWA populations and are developing protocols for rearing HWA predator insects in a laboratory setting. Our long-term goal is to establish multiple predator species throughout New York to manage HWA populations below a level that will cause hemlock mortality. Since HWA has been in New York since the 1980s, eradicating this pest from our forests is unlikely. Biocontrol represents a long-term, landscape-scale management solution as HWA continues to spread.
At this time we are only releasing biocontrols on conserved public lands in partnership with our state and regional collaborators. Since we are still in the research and development stage, this means that we cannot offer private landowners biocontrol bugs at this time. We will continue to release with the long-term goal of HWA management across public and private lands in mind.
The Hemlock Woolly Adelgid Biocontrol Research Lab is headed by forest entomologist Mark Whitmore and is housed on Cornell University’s main campus in Ithaca, NY. Our lab is part of the Cornell College of Agriculture and Life Sciences (CALS) and is mainly funded by the NY Dept. of Environmental Conservation (DEC). Other funders of our work include NYS Dept. of Environmental Protection (DEP), the US Forest Service (USFS) as part of the Great Lakes Restoration Initiative (GLRI), USDA-APHIS, and the US Environmental Protection Agency (EPA).
Our biocontrol lab held its official opening in November 2017, but the Hemlock Initiative has been releasing biocontrols in New York since 2009. We currently house two colonies of Laricobius beetles, one of La. nigrinus and one of La. osakensis. In addition, we are responsible for handling spring shipments of two silver fly species from the Pacific Northwest: Leucopis argenticollis and Le. piniperda, and processing them for release. We are also working on developing protocols for raising Leucopis silver flies in the lab, which would greatly improve our capacity for releases and HWA management.
In addition to rearing biocontrol insects, we are also using genetic techniques to understand more about their behavior and assess the success of our biocontrol program. This includes using genetic markers to analyze DNA of silver flies from each species and range to identify lineages with the most successful rates of establishment and spread.
Our Biocontrol Approach
In our lab, the beetle and fly species that we work with complement each other since they feed at different times of the year. The beetles are fall-feeders, reducing the populations of sistens-generation HWA that will survive to lay eggs of the year’s second HWA generation. The silver flies are spring-feeders that each the eggs of HWA’s second generation to reduce the amount of individuals that will hatch. Reducing both the amount of egg-laying HWA and hatching HWA helps protect hemlock twigs from the damage of HWA feeding.
Illustration by Charlotte Malmborg