Is there hope in the fight against the emerald ash borer?

Published in the Wisconsin State Journal here

UW-Madison insect researcher Patrick Liesch spent more than a decade studying the emerald ash borer — an invasive, ash-tree killing beetle the size of a grain of rice — before he finally saw it in person.

“I recognized what it was right away,” Liesch said, pointing out the adult animal’s bright green body and coppery, rounded abdomen. “I’m an illustration of how this insect can be hard to actually detect.”

First detected in the United States in southeastern Michigan in 2002, likely arriving on wood-packing ships from China, the emerald ash borer has devastated the country’s ash tree population, causing the destruction of tens of millions of trees and billions of dollars in economic damage, according to the U.S. Department of Agriculture.

The beetle travels effortlessly in temperatures as low as minus 20 degrees by way of human movement, hidden inside of firewood, logs and nursery stock. Detection can take years.

Since the bug was first confirmed in Wisconsin in 2008, it has been found in all but four of the state’s 72 counties. The most recent detection was in Polk County on May 17.

Madison has spent more than $7 million fighting the beetle, chopping down nearly half of the city’s 21,000 roadside ash trees and treating the remaining half on a rotating schedule every three years, said Craig Klinke, forestry operations supervisor.

Most experts say the beetle is here to stay, unless new scientific breakthroughs emerge.

“It’s really going to be wreaking havoc for years and really decades to come,” Liesch said.

But all is not lost.

Briana Frank is the owner of Tree Health Management, a Madison-based private tree care company. She has been helping people deal with the ash borer since it reached Wisconsin and has closely followed the beetle’s journey.

Without management, ash trees targeted by the pest can die within two to five years as the beetle slowly eats the tissue under the tree bark. In the process, starving ash trees become brittle and easily breakable, susceptible to falling and potentially harming pedestrians walking below their branches. The canopy thins as the tree is able to support fewer and fewer leaves.

Frank said the first lines of defense against ash tree death is prevention and early detection.

Studies have shown that if a tree has lost more than half of its canopy due to an infestation, it’s probably too far gone to be saved.

But as long as the tree’s vascular system — which moves nutrients, water and other supportive materials throughout the plant — is in good condition, injecting insecticides has shown great promise, Frank said.

A licensed pesticide applicator drills through an ash tree and injects the insecticides, which kill the beetle’s larvae.

“It’s extremely effective if it’s done properly, and it’s done in a good candidate,” Frank said.

Treatment costs about $220 for a 14-inch diameter ash tree and should be applied every one to three years.

“The most successful protocols have been on trees before they had a high level of infestation,” she said. “That’s always the most challenging part, because I think as humans, we notice things we (can) see.”

Not all trees are treated, though, and larger trees often can’t be. If targeted ash trees surpass a critical threshold of thinning of its canopy — the layer of leaves, branches and stems that cover the ground when a tree is viewed from above — the situation becomes irreversible and incurable, Frank said.

In those cases, the last option is removal, which can cost thousands of dollars depending on the tree’s size, cause home valuations to drop, and change the aesthetics of a neighborhood.

“If all of a sudden your entire side of the street doesn’t have ash trees on it, and the next street over has large mature trees, that really changes the look and feel of a neighborhood,” Liesch said.

After Dutch elm disease destroyed most of Wisconsin’s elm trees in the mid-20th century, ash trees were chosen as replacements, applauded for what was believed to be their sturdy and contagion-resistant nature. Madison planted hundreds of ash trees, and by the 21st century, about a third of the city’s privately owned trees were ash trees.

Flash forward to summer 2008, when the borer made its way to Wisconsin.

Quarantines were imposed in individual counties with emerald ash borer detections, making it illegal to move many ash forest products and hardwood firewood from a quarantined county to a non-quarantined county.

But still, by 2018, the situation escalated to such an extent that Wisconsin was forced to impose a statewide quarantine, requiring businesses that wanted to move restricted wood around the state to follow certain regulations.

Firewood restrictions are enforced on state and federal lands, and it’s strongly encouraged to either use certified or local firewood to prevent the emerald ash borer, as well as other pests and diseases, from further spreading.

After the beetle was found in Wisconsin, Madison established an Emerald Ash Borer Task Force.

The forestry department began by manually taking inventory of the number of ash trees lining Madison’s streets, Klinke said. About 22,000 ash trees were ultimately discovered, comprising about a fifth of the city’s street-side tree population. About 50,000 more ash trees were suspected to be on private and park properties at the time.

“We knew about it,” Klinke said. “We knew it would likely become a problem in Madison.” On a fall day in Warner Park on the North Side in 2013, the beetle was officially confirmed to be in Madison.

At its peak in the 2010s, Madison was spending about a million dollars annually on managing the emerald ash borer, Streets and Urban Forestry Division Superintendent Charlie Romines said.

“We hit it hard as soon as possible to move past it as soon as possible,” he said.

The city’s widespread removal of ash trees, an expensive endeavor, is over.

Now, the city is focused on treating the ash trees that remain, which costs about $200,000 each year, Romines said. To help with the cost, the city has tapped into urban forestry special charge funds, a monthly cost of about $6 Madisonians incur in their municipal services bill to support forestry initiatives.

Kline said the city also is experimenting with newer treatment methods, such as cordless injections, and spending less money on borer-related matters.

“We always want to try out whatever is available and see what works best for our ambiguous situation,” he said.

Additionally, Madison is planting a wider diversity of vegetation and taking inventory of street trees to be prepared if another pest makes its way to the Great Lakes region.

There are other glimmers of hope that might yield broader solutions in the future.

In Michigan, where the pest was first detected, some ash trees have shown signs of survival, a phenomenon known as “lingering ash.” In these cases, a small subset of untreated trees stays healthy even as the ash around them die as a result of the emerald ash borer. It is still unknown exactly why, how and when it happens.

“I think it does offer hope that, in the long run, we might be able to take some surviving trees and perhaps reintroduce some sort of tolerant or resistant ash to repopulate areas,” Liesch said.

Scientific efforts are underway by government agencies, including the U.S. Department of Agriculture, to mitigate the pest using biological control, the method of introducing highly specific natural enemies from a pest’s homeland to lessen its presence.

Wisconsin has experimented with biological control against the beetle for more than 12 years, but it could be decades before the strategy proves effective, if at all, Liesch said.

So, for now, for a beetle that can barely be seen, the emerald ash borer is certainly making its presence known.

“We don’t really know what the end game is going to look like with this,” he said. “These pests are really changing what forests, natural forested areas but also urban forests, look like. It’s night and day.”