The Future of Pennsylvania Forests: The Emerald Ash Borer Strikes

(Scott Bliss/Allegheny Front)

DCNR's Dr. Houping Liu displays wasps being used to kill the Emerald Ash Borer.

Ken Tomajko is working in a backyard in the South Hills of Pittsburgh. He’s using one of the latest weapons in the war on the Emerald Ash Borer.

“One of the first steps is that I have my diameter of the tree,” Tomajko said. “Come over to my chart and it’s telling me I need 50 milliliters of the active product.”

Tomajko’s an arborist with Arborel Tree Service. He’s applying an insecticide known as TREE-age to some ash trees. An inspector had told the homebuyer, Steve Levine, that he and his wife might want to protect their many ash trees from the emerald ash borer. So they called in Tomajko.

“My back yard is filled with a lot of trees,” Levine said, “and it was one of the features that very much attracted us to the house, and we kind of felt that, if we were able to do so financially, we wanted to make an effort to save as many of the trees as possible.”

Arborel charges $200 to $600 dollars, depending on the size of the tree. Homeowners like Levine can’t just spray a tree on their own with TREE-age. Tomajko explains that the application involves drilling and plugging holes.

“Drilling the tree, making sure that the system is closed, making sure that the plug, when I put it in is at an angle, is it flush so that there’s no leaks to come out the side,” Tomajko said. “Then when I put this product in there we’ll hook up right into those little arbor plugs right there and then the product will go up inside the tree.”

Protecting Forests

Treating one tree takes about 15 minutes, and lasts up to three years. Many homeowners may not know their ash trees need protection. The tree Tomajko’s injecting with TREE-age looks pretty healthy to an untrained eye. But that doesn’t necessarily mean anything. The pest that’s attacking this type of tree is small. When the damage reaches the human eye level, it’s too late.

While TREE-age is useful for property owners and communities, it’s too expensive and time consuming for the thousands of trees in our native forests. In Pennsylvania, ash trees are most prominent in the northern tier. The emerald ash borer doesn’t have any natural enemies in the U.S., and our Ash trees lack any natural resistance to it.

So for forests, the only hope is a biological control.

“We just open it up, put them next to the tree, kind of urge them out a little bit. They fly away,” said Dr. Donald Eggen.

(U.S. Forest Service)

Tetrastichus planipennisi, one of the two species of stingless wasps being released in Pennsylvania.

Eggen is the Forest Health Manager with the Bureau of Forestry in the Pennsylvania Department of Conservation and Natural Resources (DCNR). In a state forest in central Pennsylvania, he’s releasing tiny wasps that are aggressive enemies of the emerald ash borer (EAB) in the beetle’s native Asia.

“These are very small, tiny wasps…” Eggen said, “…These guys are specialized in attacking other insects … so these are tiny wasps that look for EAB larvae under the bark…”

Eggen said the DCNR expects the wasp program to take at least a decade before the agency knows whether it’s made a difference. Even then, the insect won’t be eradicated, just controlled to a manageable level. Eggen said the wasp program doesn’t help our existing Ash trees, only their successors.

“From the standpoint of the forests,” Eggen said, “these trees are going to die. In this forest that we’re here, virtually all of them are going to die eventually, within three to five years, if not sooner.”

Economic Impact

State agencies don’t yet know how hard the loss of ash trees will hit Pennsylvania’s economy. The emerald ash borer is close, but hasn’t quite made it to Pennsylvania’s northern forests where ash trees feed a profitable baseball bat industry.

A recent study in the journal of environmental management estimates the cost to communities nationwide will be $12.5 billion. So far, Congress has appropriated about $280 million to the USDA. The U.S. Forest Service has spent around $30 million of its own money on research and bio-controls since 2003.

Spread of the Emerald Ash Borer

The emerald ash borer was first detected in and around Detroit in 2002. It probably hitched a ride from Asia in packing materials made of wood. Since then, it has spread into 15 other states, including Pennsylvania, and seems unstoppable.

“It’s like a perfect pest for trees,” said Phillip Bell. Bell manages the Eastern Region Emerald Ash Borer Program for the USDA’s Animal and Plant Health Inspection Service.

“It's small,” Bell said. “Early infestations can go undetected for a number of years, and by the time we find the pest with the tools that are available right now, it can have spread to other locations, either just natural spread or via fire wood or logs.”

The borer was first found in Pennsylvania in 2007 in and around Cranberry Township, a fast-growing suburb north of Pittsburgh. Researchers have discovered that the insect landed in the area seven or eight years before it was detected. Since then it has spread to at least 22 other counties. The state developed a detailed Emerald Ash Borer Action Plan in 2006. A plan, yes, but, as it turned out, Bell said, not a very successful one.

“The plan as written and developed is great,” Bell said. “Would be perfect if we had a small infestation, but the fact is the infestations are more than what we thought, so it’s hard to garner the resources to address all those new infestations.”

But Pennsylvania agencies are still trying. A new action plan asks urban communities to figure out if they want to treat stricken trees individually, or replace them with other tree species. The plan also calls for foresters to reduce the percentage of ash trees they grow.

So, what have we learned from the whole emerald ash borer experience? USDA scientists say a lot. They believe their work is uncovering other insect pests that are approaching the United States, and is giving agencies impetus for closer inspections of goods coming into the country — something that could have stopped the emerald ash borer in the first place.