Gypsy moths

Gypsy moth caterpillars feed on leaves, especially oak leaves.

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The gypsy moth is having a particularly good year in Pennsylvania. That’s particularly bad for trees.

“They really like oak,” said Dr. Mark Faulkenberry, an entomologist with the state Department of Conservation and Natural Resources. “Any variety of oak, they really love to eat the leaves. They will eat it down all the way to where the veins of the leaf are.”

Faulkenberry has been working long days recently with others in the Bureau of Forestry to fight back against the larval pest.

Every year, fixed winged aircraft and helicopters spray large areas of public and private land across the state with a caterpillar-killing pesticide that is not harmful to humans or other species. Every few seasons, caterpillars that survived from the previous year lay an exorbitant amount of eggs.

“We alone at DCNR are treating about 136,000 acres,” Faulkenberry said. “So, it is a pretty high infestation.”

According to Faulkenberry, the largest infestation of gypsy moth caterpillars is currently in the north-central and northeastern counties. However, spraying has also occurred or is scheduled in portions of Cumberland, Perry, Dauphin and Lebanon counties.

Visitors to state forests and state parks can find an updated list of sites that are scheduled to be sprayed or have already been sprayed by using an interactive map on the DCNR website.

The gypsy moth itself as an adult moth is harmless to trees. However, in its larval caterpillar form, it can defoliate forests very quickly. Faulkenberry says control is vital when the pests are young; before they dramatically impact the native ecosystem.

“Let’s say the tree dies,” he said, “you have an opening in the canopy now. Sometimes an invasive plant might move in there because they’re quicker to get established.”

Recent rain has placed crews behind schedule in aerial spraying, but Faulkenberry says the work should be completed by Memorial Day.

The gypsy moth caterpillar is not native to Pennsylvania. It is believed to have been introduced to the United States decades ago from overseas by someone wanting to breed the species with a native silk worm for use in the silk industry. The experiment failed and several of the gypsy moths escaped, gaining a foothold in nature. The species is now believed to exist in at least 11 eastern states.

Ironically, while rainy weather this spring season has kept aircraft from flying regularly to spray infested areas, the rain may be assisting a natural method for gypsy moth containment.

According to Faulkenberry, a fungus that was introduced decades ago to control the larva has begun to establish itself in Pennsylvania forests where the gypsy moth has become a problem. A virus that naturally controls the population is also known to flare up during periods when the population is at its highest.

It is yet to be seen if either has an impact this year. Gypsy moths caterpillars are also preyed upon by birds and other insects, providing natural forms of control.

For more information about the gypsy moth, visit the PA DCNR website at www.dcnr.state.pa.us.

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