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Gypsy Moth Populations Plummet Across PA, Reduces Need For Spraying In 2010
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After the collapse of the state’s gypsy moth caterpillar population in 2009, the Department of Conservation and Natural Resources Bureau of Forestry will not conduct aerial suppression efforts against the invasive species, but today warned that another destructive insect will take a toll on some northern forests.
“Overall, gypsy moth defoliation was significantly reduced in 2009 and is expected to be very low in 2010,” said State Forester Daniel Devlin. “The cool, wet weather conditions in the spring of 2009—which coincided with the species’ larval development period—is believed to have promoted the natural fungus that cuts heavily into insect numbers and their defoliation, Entomophaga maimaiga.”
Devlin noted summer and fall surveys in 2009 showed gypsy moth egg mass densities were so low that no counties or other cooperators requested aerial suppression treatment this spring by the Bureau of Forestry. This marks the first time in four years that the Department of Conservation and Natural Resources will not apply aerial treatments.
Last year, 25 counties and other cooperators requested treatments be applied to 177,668 acres in the southcentral, central and northeastern regions of the state.
Dr. Donald A. Eggen, chief of the bureau’s Forest Pest Management Division, said gypsy moths have severely impacted Pennsylvania forests since the early 1970s, with outbreaks occurring every five to seven years. Their numbers peaked in 1990 when they defoliated 4.3 million acres.
“If gypsy moth infestations follow past outbreak cycles, we expect them to rebound by 2012. Warm, dry springs in April, May and June this year and next will favor gypsy moth populations,” Eggen said, adding his division again will monitor projected gypsy moth populations in spring 2011 and will keep county officials informed on infestation threats, as well as funding issues that could affect future suppression efforts.
Devlin said this year, however, the bureau is monitoring private spraying efforts to combat forest tent caterpillar defoliation in several northern counties.
“For the first time in recent years, the forest tent caterpillar surpassed the gypsy moth to become the top forest insect defoliator in the state in spring 2009,” Devlin said. “Forest tent caterpillars defoliated more than 371,000 acres, while the gypsy moth accounted for 239,700 acres of defoliation—far less than the 766,500 acres of woodlands stripped in 2008.”
The forest tent caterpillar caused heavy defoliation last spring in sections of Potter, Cameron, Elk, McKean and Tioga counties, primarily targeting sugar maple, oak, poplar and other deciduous hardwoods,. Past outbreaks have been reported in Pike, Monroe, Luzerne, Lycoming, Wayne and Sullivan counties.
“Unlike the gypsy moth, the forest tent caterpillar is not an invasive insect, but rather a native, recurring forest pest in many areas,” Devlin said. “Because of the timing—during the earliest stages of leaf-out—its defoliation poses less of a threat to tree health than the gypsy moth. Forest mortality can occur, however, when these defoliated trees also are subjected to weather, disease and other insect threats.”
For more information, visit DCNR's Forest Health webpage.
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5/10/2010 |
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