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State Forests Under Attack - June 2002
June 4, 2002
UNIVERSITY PARK, PA -- The over two million acres of state forests in Pennsylvania provide many benefits to its users, including clean air and water and provides habitat for wildlife. Mike Blumenthal, Forest Health Supervisor for the Pennsylvania Bureau of Forestry, is taking strides to ensure state forests stay that way.
Blumenthal's work in the Division of Forest Pest Management has focused on biological control of forest insect and disease pests. Biological control is part of an integrated pest management (IPM) system. IPM aims to manage pests -- such as insects, diseases, weeds and animals -- by combining physical, biological and chemical tactics that are safe, profitable and environmentally compatible. Biological controls include the predators, parasites, and diseases that are natural enemies of pests.
The primary forest pests in Pennsylvania over the last several years have been gypsy moth and hemlock woolly adelgid, "There's good news about the gypsy moth - its population has been declining for the last two years," says Blumenthal. This spring the bureau sprayed about 50,000 acres to control the gypsy moth in forested residential and high-value public timberlands, as opposed to as much as a half million acres in previous years. "A virus and fungus has decimated gypsy moth populations, thanks to this cooler, wet spring which has helped foster these diseases," Blumenthal explained. "We should see a dramatic reduction in gypsy moths in 2003."
While this is good news, it has only allowed Blumenthal more time to tackle another major problem, hemlock woolly adelgid (HWA). "Originally from Asia, HWA was first discovered in the eastern United States in 1957. It's widespread in the eastern portion of the state now and is spreading north and west rapidly," says Blumenthal. It has been detected as far west as State College in Centre County. In fact, the insect population has been growing so rapidly, Blumenthal and his colleagues don't have a handle on how much damage the pest has caused hemlocks, the pest's primary host. "Hemlock trees aren't as much a commercial tree like oak, but they tend to grow in clusters along streams, providing ecological and aesthetic value," he states.
Blumenthal hopes to begin tracking spread of the pest and its damage with sophisticated GIS satellite imagery. Since there are no pesticides approved for overhead sprays to control hemlock woolly adelgid and injectable insecticides can be used only on an individual-tree basis, Blumenthal has turned to using natural enemies to control the pests. " I went to China in 1994 to find natural enemies of hemlock woolly adelgid, and we found predatory ladybird beetles that feed on the HWA," he says. The USDA Forest Service has two labs in the United States raising one species, and northeastern states have been releasing them in hopes of establishing them. Blumenthal began releasing these lady beetles Pennsylvania in 1999, with over 110,000 beetles released to date in 18 counties. They appear to be overwintering successfully and reproducing well in some areas, but actual control of the HWA may be many years away.
Blumenthal has also been researching other species of Asian ladybird beetles for potential release. He emphasizes, however, that these ladybird beetles are a different species than the ones that can infest your home every spring and fall. "These lady beetles are much smaller, about pinhead size, and black. They are also difficult and expensive to raise," says Blumenthal. They are also experimenting with other insect predators that have been effective against the pest. "Unfortunately, there are no known diseases or parasites of hemlock woolly adelgid, so insect predators are our only current option for biological control, " Blumenthal explains. This summer, the bureau plans on doing several aerial surveys to map defoliation and tree mortality to determine the statewide geographic health of Pennsylvania forests.
For more information on hemlock woolly adelgid, see the bureau's Web site at http://www.dcnr.state.pa.us/forestry/woollyadelgid/index.htm or the Penn State Entomology web site http://www.ento.psu.edu/extension/factsheets/hemlockwoolly.htm. To find out more on forest health and management in the Northeast, see USDA Forest Service Northeastern Area's Web site at http://www.na.fs.fed.us/. You may also contact Mike Blumenthal at (717) 948-3950, cell phone (717) 514-6700, or by email at eblumentha@state.pa.us.
The Pennsylvania IPM program is a collaboration between the Pennsylvania State University and the Pennsylvania Department of Agriculture aimed at promoting integrated pest management in both agricultural and nonagricultural situations. For more information, contact the program at (814) 865-2839, or Web site http://paipm.cas.psu.edu.