“That’s second only to New York state in terms of the number of pests,” said lead author Gary Lovett, senior scientist at the Cary Institute of Ecosystem Studies in upstate New York.
Lovett said the financial burden of forest pests are primarily borne by municipalities and homeowners, to the tune of $4.5 billion annually nationwide.
“The major cost is the takedown and replacement of trees that die in people’s yards, in city streets, in city parks,” he said. “Those trees are a danger and they need to be taken down and replaced and that’s a very expensive proposition.”
The greatest threats to Pennsylvania trees are the emerald ash borer and the hemlock woolly adelgid, said Lovett.
The emerald ash borer was first detected in the U.S. outside Detroit in 2002 and has since decimated the ash tree population in Pennsylvania, according to the state Department of Conservation and Natural Resources.
Mark Faulkenberry with DCNR’s Division of Forest Health said the beetle native to eastern Asia is extremely fast-acting.
“So, by the time you see that you have an infestation, it’s almost too late to treat,” he said.
In the past, an infestation meant that the tree had to be removed, but the DCNR is currently trying two new approaches to stopping the beetle: insecticides and parasitic wasps. Insecticides have proven effective at killing adult ash borers within four days, according to the U.S. Forest Service. But the parasite approach is relatively new to Pennsylvania and could take years to yield results, said Faulkenberry.
The oobius agrili wasp lays its own eggs within the ash borer eggs while the tetrastichus planipennisi larvae feed on the ash borer larvae. Both are native to Asia and are natural enemies of the emerald ash borer. Faulkenberry said this approach is being tested at a handful of sites within state forest land, but he said the locations of those sites must remain secret to maintain the integrity of the experiments.
The hemlock woolly adelgid, an aphid-like insect, has also spread rapidly through Pennsylvania and much of the east coast. Efforts to control the pest have been similar to emerald ash borer eradication efforts, but Faulkenberry said the effectiveness of those tactics remains to be seen.
Faulkenberry is also worried about the Asian longhorned beetle, “a highly destructive beetle … with an even wider host range” that impacts not only ash trees but also birch, maple, poplar and other species. While not yet present in Pennsylvania, Faulkenberry said DCNR officials are concerned about it spreading from neighboring New York and New Jersey.
But Gary Lovett said that preventing the foreign pests from entering the country in the first place is a far more effective strategy than trying to kill them off once they’re here. That will require a greater commitment from the federal government and private companies alike, said Lovett.
“The (pests) either come in buried in wood packaging, like crates and pallets, or they come in riding on live plants that are brought in for the horticultural trade,” he said.
Lovett and researchers at Harvard University are advocating for better early detection and response on the part of the U.S. Animal and Plant Health Inspection Service, which oversees the shipping of live plants, and the customs officials that inspect other types of good imported in crates or on pallets.
The authors are also advocating for a federal program that would provide incentives to companies that ship using non-solid wood containers and pallets.
“For instance some companies use crates that are made out of manufactured wood products like oriented strand board or chip board,” Faulkenberry said. “Some companies use pallets made out of recycled plastic, some companies pallets made out of paper-type material, corrugated type material.”
He said some companies, including Trader Joe’s and IKEA, have already phased out the use of solid wood shipping containers and pallets.