Goal: Deliver Benefits to the Public Managing hemlock woolly adelgids
Land managers aiming to protect hemlock trees and control hemlock woolly adelgids (HWA) have a new resource from the USDA Forest Service: a technology transfer publication with guidelines on integrating chemical and biological control of the invasive hemlock woolly adelgid.
The strategy for prolonging hemlock health includes limited use of insecticides combined with establishing HWA predators on untreated or previously-treated trees. Guidelines are provided for implementing, monitoring, and assessing the strategy.
Researchers are also evaluating the effectiveness of silvicultural treatments as well as biocontrol—insects that eat hemlock woolly adelgids.
A nonnative invasive insect, the hemlock woolly adelgid (HWA), threatens the ability of natural resource managers to maintain eastern and Carolina hemlocks as critical components of unique forest ecosystems in eastern North America. Although substantial progress has been made in both chemical and biological control of HWA, neither of these tactics applied alone is expected to provide adequate control of HWA throughout its introduced range.
A new USDA Forest Service resource manager’s guide titled “Integrating Chemical and Biological Control of the Hemlock Woolly Adelgid” presents a strategy for using biological and chemical control together in the same forest stands. The goal of the strategy is to prolong hemlock health on certain hemlock trees through temporary insecticide protection, while simultaneously establishing predators on nearby untreated trees.
Temporarily-protected hemlocks are expected to eventually support predators after their chemical treatment wears off. A separate research project showed that Laricobius nigrinus, a predatory beetle, significantly reduced populations of the winter generation of the hemlock woolly adelgid. However, this beetle inactive in the spring, suggesting the need for additional predators and control measures.
Another research project confirms that silvicultural treatments that allow more sunlight to shine on eastern hemlock trees can make them healthier, even if they are infested with hemlock woolly adelgids. Researchers are working to develop management recommendations, and plan to update the manager’s guide.
Related article: To save the hemlock, scientists turn to genetics and natural predators - The Washington Post
- Principal Investigators
- Albert E. Mayfield III, Research Entomologist
- Chelcy F. Miniat, Project Leader
- 4552 - Insects, Diseases, and Invasive Plants
- 4353 - Center for Forest Watershed Research
- Strategic Program Area
- Invasive Species
- Integrating chemical and biological control of the hemlock woolly adelgid: a resource manager’s guide
- Physiological responses of eastern hemlock (Tsuga canadensis) to light, adelgid infestation, and biological control: Implications for hemlock restoration
- Impact of the introduced predator, Laricobius nigrinus, on ovisacs of the overwintering generation of hemlock woolly adelgid in the eastern United States
- Rebound of Adelges tsugae spring generation following predation on overwintering generation ovisacs by the introduced predator Laricobius nigrinus in the eastern United States
- CompassLive Articles
- New Manager’s Guide for Controlling Hemlock Woolly Adelgids
- Hemlock Woolly Adelgids & Their Predator Beetle, Laricobius nigrinus
- Hemlock Seedlings Released from Shade
- Research Partners
- Noel F. Schneeberger - Forest Health and Economics, Eastern Region
- Rusty Rhea - Forest Health Protection, Southern Region
- David R. Zeitlow - NRS
- Cindi Brown - Coweeta Hydrologic Laboratory, NRS
- External Partners
- Scott M. Salom - Virginia Tech, Department of Entomology
- Kenton Sumpter - West Virginia Department of Environmental Protection
- Tom McAvoy - Virginia Tech, Department of Entomology
- Steven T. Brantley - Jones Center at Ichauway
- Robert M. Jetton - North Carolina State University, Department of Forestry and Environmental Resources, Camcore