New Predator Enlisted in Fight Against Hemlock Woolly Adelgid

MORGANTOWN, WVa—State and Private Forestry officials with the USDA Forest Service will release a new predatory beetle on the Monongahela National Forest on Wednesday to counter the invasive hemlock woolly adelgid.  Officials will release 400 to 500 Scymnus sinuanodulus lady bird beetles in the Blue Bend Recreation Area.

S. sinuanodulus is native to China and feeds primarily on hemlock woolly adelgids. Although this lady bird beetle prefers hemlock woolly adelgid eggs, it will feed on all life stages of the adelgid.
This predatory beetle shares a unique feature with the hemlock woolly adelgid—their life cycles are synchronized. Both insects are active and reproduce during the fall and winter months followed by dormancy during the summer, which is an unusual pattern for insects.

The hemlock woolly adelgid is a non-native pest that was first discovered in the Eastern United States in the 1950s.  By the early 1990s, adelgid infestations began causing extensive hemlock tree mortality throughout the East.  Heavy infestations can kill a hemlock within 2 to 7 years. The hemlock woolly adelgid is easily identified by the white woolly material it produces on hemlock twigs.

The eastern hemlock is a critical component of native trout habitat and does not have an ecologically equivalent tree species that can take its place. It grows in dense stands, providing shelter when harsh weather conditions exist. Research presented at a hemlock woolly adelgid symposium in 2002 showed that brook trout populations were 300 percent greater in hemlock-shaded streams than in streams bordered by hardwoods. Hemlock-shaded streams were also found to have lower summer temperatures and were less likely to dry up. Hemlocks maintain aquatic habitat integrity by regulating streamflow and moderating water temperature.

In 2004, the USDA Forest Service released two other species of lady bird beetles on the Monongahela National Forest to limit hemlock mortality. Scientists are evaluating each of these beetles to find the most effective way to protect hemlock trees.

Studies indicate that S. sinuanodulus beetles do not gather together in large numbers prior to overwintering as does Harmonia axyridis, another nonindigenous beetle that was introduced most recently into the U.S. by the USDA Agricultural Research Service in the late 1970s and early 1980s to control aphids and other insect pests that injure trees, shrubs, and agricultural crops.
        
For more information about Scymnus sinuanodulus, go to http://www.na.fs.fed.us/fhp/hwa.  Photos of the beetle are available at http://www.na.fs.fed.us/nanews/archives.shtm.

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