The cool, wet weather of spring 2013 has emerged as a strong ally of state woodland managers as they prepare to combat remnants of a statewide gypsy moth population that had been posed for a heavy outbreak across much of the state, Department of Conservation and Natural Resources officials said Thursday.
“Heavy defoliation in some areas last spring left our forest pest management experts bracing for increased statewide spraying across the state, but our entomologists say most of that gypsy moth population collapsed, thanks to a naturally recurring fungus,” DCNR Secretary Ellen Ferretti said. “Last spring’s cold, wet weather proved ideal for the fungus, deadly to gypsy moths.”
Still, Ferretti said, the state Bureau of Forestry will target tracts in four counties in an aerial spraying effort to suppress the woodland insect pest. Forty-two tracts totaling 1,901 acres will be sprayed in Clarion, Clearfield, Crawford and Venango counties.
“This is a far cry from spring 2013 when gypsy moth numbers required the spraying of more than 43,000 acres of woodlands in northwest and north-central sections of the state,” Ferretti said. “Only private land will be sprayed at the owners’ request; no public land will be sprayed this spring.”
After a three-year absence of severe gypsy moth damage in state woodlands, the invasive forest pest in some areas multiplied in 2013 to the point where more than 148,000 acres were defoliated, and an additional 170,600 acres were damaged by the insect and heavy, late spring frosts.
Before spring 2013, DCNR last sprayed for gypsy moths in 2009, when more than 178,380 acres in 25 counties were targeted across the state. In 2008 a total of 221,221 acres of private, state and federal woodlands were sprayed in 27 counties.
“Private woodland owners and state forest visitors must remember spraying is a suppression effort, a forest management effort to protect trees from moderate to severe defoliation,” said Dr. Donald Eggen, the bureau’s forest health manager. “The gypsy moth will continue its cyclic population with ups and downs, and we cannot eradicate the insect. It’s too well-established and is here to stay.”
The bureau will spray 1,447 acres of private woodlands in Venango County; 199 in Crawford; 150 in Clearfield; and 105 in Clarion.
“Counties opt to enroll and share in the costs of treatment in this voluntary program,” said Eggen said. “Spraying was not needed on any state lands because the gypsy moth’s natural enemy, the fungus Entomophaga maimaiga, caused populations to collapse in woodlands across the state.
“Spraying helps contain the widespread gypsy moth damage we’ve often seen in the past, but the major controlling factor is, and will continue to be, the prevalence of this fungus in our woodlands,” Eggen said.
Utilizing helicopters, the spray program is set to begin late this week and last just a few days. Again this spring, tree foliage will be treated with the biological insecticide, Bacillus thuringiensis (Bt), comprised of naturally occurring Bacillus spores which must be ingested by the caterpillar. No chemical insecticides are used.
Forestry bureau experts identify the gypsy moth as one of the most destructive forest pests in Pennsylvania. Feeding while in the larval -- or caterpillar -- stage, the insect usually hatches and begins feeding from mid- to late April in southern Pennsylvania, and in early to mid-May in the northern part of the state.
Oak, apple, sweet gum, basswood, birch, poplar and willow trees are affected the most by the gypsy moth. Older larvae also will feed on hemlock, pines, spruces, southern white cedar and other conifers.
When populations peak, the insects may strip trees of foliage, leaving them weakened and susceptible to disease, drought and attack by other insects. A tree begins to suffer when 30 percent or more of its leaf surface is lost.
Begun in 1972, forest insect spray programs are a cooperative effort among DCNR's Bureau of Forestry, county governments and the U.S. Department of Agriculture Forest Service's Forest Health Protection Unit.
The gypsy moth was introduced to North America in 1869 at Medford, Mass., where it was used in a silk-production experiment. The gypsy moth first reached Pennsylvania in Luzerne County in 1932, and since then has infested every county.
Homeowners and other private property owners can check mapped spraying areas at DCNR’s Interactive Gypsy Moth Spray Status Map. Learn more about the gypsy moth generally, on DCNR’s Gypsy Moth webpage.
