Experts warn: Ash-killing emerald ash borer is at our doorstep

Emerald Ash Borer
An adult emerald ash borer.

Time, arborists say, is running out: The deadly emerald ash borer is coming to a tree near you.

Since first spotted in Detroit in 2002, the voracious insect native to East Asia has wiped out ash trees across the northern United States and is now at our doorstep. The species has been spotted in Warrington and Horsham in central Bucks County, and in Moorestown, Burlington County.

The insect could "kill all the ash trees in the city, starting in five to seven years," Parks and Recreation tree expert Curtis Helm warned the tree-care professionals who gathered Wednesday at Morris Arboretum to discuss methods for combating the pest.

The emerald ash borer, or EAB as it is known in horticultural circles, lays its eggs on ash trees, and the resulting larvae disrupt the upward flow of water and nutrients into the trees before boring out. That disruption weakens and eventually kills the host tree.

"This has been likened to both chestnut blight, . . . which wiped out almost all of our American chestnut trees, and Dutch elm disease, which was similar," said Helm, who has been leading Parks and Rec's efforts against the emerald ash borer since 2012.

Other cities have "learned the hard way that they need to plan ahead, because it doesn't seem real until it strikes. . . . All of a sudden thousands of trees start to die," Helm said.

Since 2014, the city has been working to locate and treat or remove all ash trees near walking paths, utility wires, buildings - "anywhere people would be within striking distance of a tree if it were to fall," Helm said.

About 200,000 of Philadelphia's 3.1 million trees are ashes, including 600 on city streets. As of last summer, about 1,200 trees were treated and 450 less-than-healthy trees removed.

The only way to deal with the infestation is to remove ash trees or inject them with pesticide once every few years.

Most of the 16 attendees at Wednesday's workshop were tree-care professionals from private companies gearing up for what they see as a coming demand for their services from property owners.

Daniel Murphy said his company, Murphy's Tree Service in Wayne, has decided to add insecticide services to be able to treat trees for the EAB.

"They're talking about a citywide plan, and . . . if we're going to serve our clients properly, we need to be up-to-date on this," Murphy said.

This means training employees, and getting them state certification as pesticide applicators.

Joel Spies, the president of Rainbow Treecare, a Minnesota-based research company, said Helm's approach in Philadelphia is "pretty progressive" and can serve as a model for other cities.

"When EAB first arrived [in the country] the plan was to cut down all the ashes. . . . Scientists knew you could use preventive treatments, but the cities took no action," said Spies, who has worked with city officials and private companies throughout the nation.

Helm said the emerald ash borer is "on our doorstep if they aren't already here. We'd like to see as many trees on private property get treated as possible."

If not treated, infected ash trees soon die and shed large limbs as they become brittle.

Identifying and assessing ash trees now can save money and grief down the road, participants said.

Spies said EAB treatment is very straightforward compared with other invasive problems, but "where it gets complicated is the human factor - no one does anything soon enough, but that's only delaying costs. The insects will be there."

tyang@phillynews.com