Emerald ash borer moves ever closer to Delaware

DOVER — Delaware stands out by what’s missing on the www.emeraldashborer.info map.

However, red dots pinpointing locations for the iridescently beautiful but voracious emerald ash borer are marching ever closer, especially with the discovery of the insect on the Eastern Shore.

Entomologist Jimmy Kroon knows it’s only a matter of time until Delaware falls to the invader.

“It’s not good news that it’s on the Eastern Shore,” he said last week, “but it’s not terribly shocking.”

The emerald ash borer likely arrived in the United States from in wood packing in cargo ships originating in Asia. (U.S. Forest Service/Debbie Miller via Bugwood.org)

The emerald ash borer likely arrived in the United States from in wood packing in cargo ships originating in Asia. (U.S. Forest Service/Debbie Miller via Bugwood.org)

Mr. Kroon, an environmental scientist with the Delaware Department of Agriculture, has believed for several years the emerald ash borer would get to Delaware, but its hop across the Chesapeake Bay and subsequent arrival on the Eastern Shore occurred “sooner than expected.”

An invasive insect from Asia, the emerald ash borer has killed millions of ash trees since it first was spotted in the United States in 2002 in Michigan. It steadily has spread eastward, reaching Maryland in 2006, Pennsylvania in 2007, Virginia in 2008 and New Jersey in 2012.

This spring the insect was spotted in Maryland’s Queen Anne’s and Dorchester counties.

The good news is that the insect’s preferred host — the ash tree — is in short supply in Delaware, especially south of the canal.

“My gut feeling is that it won’t spread very quickly, especially in southern Delaware,” Mr. Kroon said.

Northern Delaware is a different story, though. “North of the canal, especially north of (Interstate) 95, it’s easy to find ash.”

Chris Kohout, grounds supervisor for the Dover Department of Public Works, isn’t overly worried about the emerald ash borer’s impact on Dover’s streetscape since the city doesn’t have many ash trees.

Most of the problems he’s seen in the city’s trees, especially crepe myrtle and maple, this year can be traced to damage from the winter and native borers, which leave bigger exit holes than the emerald ash borer.

He said Monday the city is looking to take down three trees when time allows and state forestry staff likely will be on hand to inspect for evidence of non-native pests.

Like Mr. Kroon, Mr. Kohout expects the emerald ash borer to show up in Delaware and once that happens decisions will be made on which trees will be treated and which will be replaced.

Tree killer

The half-inch long green adult beetle’s nibbling on foliage causes minimal damage, but the larvae’s feeding on the inner bark of the ash disrupts the tree’s ability to absorb water and nutrients.

In its larva state the emerald ash borer destroys tissues under the ash tree’s bark. As the tree is unable to transport water and nutrients through its system, the leaf canopy begins dying from the top down. One-third to one-half of the branches may die in one year. (Submitted)

In its larva state the emerald ash borer destroys tissues under the ash tree’s bark. As the tree is unable to transport water and nutrients through its system, the leaf canopy begins dying from the top down. One-third to one-half of the branches may die in one year. (Submitted)

Experts believe the beetle arrived in the United States in wood packing material carried in cargo ships or airplanes originating in Asia.

So far it only has attacked ash, a common landscape tree but which also is used in flooring, cabinets and baseball bats.

However, signs, including a dead beetle, were found in a fringe tree in Ohio.

The shrub tree, so-called for its sweet-smelling dangling white flowers that bloom in the spring, mostly is used in landscaping and is a relative of the ash. According to www.sciencedaily.com it is growing in popularity as an ornamental.

Mr. Kroon is unsure what the discovery means, and whether the fringe tree is as susceptible to the beetle as the ash is.

“I’m not sure if it’s a big deal,” he said. “I don’t know.”

The U.S. Department of Agriculture estimates that if left unchecked the emerald ash borer could cost $20 billion to $60 billion in damage to the timber industry, municipalities and homeowners, who will bear the cost of taking down dead trees and then replacing them.

The emerald ash borer now is considered the most destructive forest pest ever in North America, surpassing the gypsy moth.

Firewood dangers

Even though Queen Anne’s and Dorchester counties border Delaware, the borer still is more than 15 miles out, a key distance when it comes to planning treatment programs for existing ash trees.

EAB boxThe insect was spotted westerly, near the U.S. 50 corridor.

Mr. Kroon speculated it likely traveled in on firewood.

Forest hydrologist Anne Hairston-Strang, acting associate director of Maryland Department of Natural Resources Forest Service, can’t confirm that but did say firewood often is suspected.

“The insects don’t usually fly more than a half mile on their own, so most new infestations have had some human-assisted transport,” she said in an email.

Traps indicated the beetle was around Baltimore and Annapolis in 2014.

“Appearance on the Shore was quicker than was hoped,” she added.

Both Maryland and Delaware urge people to not move firewood around in an effort to combat the emerald ash borer and other invasive, non-native insects from piggybacking into a new territory.

Too often, Mr. Kroon said, people bring their own firewood to vacation homes and camps to avoid having to pay perhaps higher prices locally.

“It’s common,” he said. “Lots of individual people are moving firewood to vacation homes.”

Some might not even be aware of the emerald ash borer problem or why ash trees are dying.

“The biggest problem may be someone who has a vacation home and is bringing in a truckload of wood,” he said.

Mr. Kroon pointed out Delaware doesn’t have a big timber industry, unlike Michigan and Ohio where “30 to 40 percent of trees are ash and they are really worried.”

The potentially costly problem in Delaware will be for municipalities and homeowners who have mature ash trees.

“Communities north of Wilmington have 50- or 60-year-old trees,” he said. “Homeowners will be responsible for hundreds of thousands of dollars to remove them if they die.”

Traps, designed to lure emerald ash borers if any are in the area, were placed around Delaware in May and will come down by late August to be inspected. This one is hanging over Sharon Hill Road, west of Dover.  (Delaware State News/K.I. White)

Traps, designed to lure emerald ash borers if any are in the area, were placed around Delaware in May and will come down by late August to be inspected. This one is hanging over Sharon Hill Road, west of Dover. (Delaware State News/K.I. White)

He recommends being proactive about regularly visually inspecting trees and replacing aged trees.

He also preaches a “plant diversity” message to individuals and towns.

Management vs. eradication

Mr. Kroon isn’t idle while he anticipates the borer’s move into Delaware. For now, the focus is on detection but once the insect’s arrival is verified the state will shift into management mode. No state has been able to eradicate the emerald ash borer, he said.

In Maryland, Ms. Hairston-Strang agreed.

“Eradication is no longer deemed feasible, with large EAB populations in western and southern Maryland and most surrounding states,” she wrote.

Response, she said, now concentrates on reducing risks to communities and treating priority trees.

Visual surveillance is key, Mr. Kroon said, especially now as adult beetles emerge from their larvae state.

Drivers may have spotted one of the 53 pale purple three-sided boxes dangling in trees alongside roads. Mr. Kroon and his co-workers placed the traps throughout the state in May, once temperatures rose to a consistently warm level.

The trap’s sticky surfaces are treated with a pheromone to lure nearby emerald ash borers. The traps will come down by late August to be inspected for signs of dead emerald ash borers.

Joining the purple traps this year is the eye-catching spiral Lindgren funnel trap. The beetle supposedly likes its bright green color.

It has higher catch rates, Mr. Kroon said.

He also is in the field, engaged in bio-surveillance of a native ground wasp, Cerceris fumipennis, that feeds on the emerald ash borer. Last week he was in Stanton doing a Cerceris surveillance.

Delaware entomologist Jimmy Kroon did a bio-surveillance of the Cerceris ground-nesting wasp in Stanton last week. The native wasp is one way officials are monitoring for the emerald ash borer. (Submitted Jimmy Kroon)

Delaware entomologist Jimmy Kroon did a bio-surveillance of the Cerceris ground-nesting wasp in Stanton last week. The native wasp is one way officials are monitoring for the emerald ash borer. (Submitted Jimmy Kroon)

His mission was to intersect a beetle-hunting wasp on its way back to its nest to see what it had caught.

“So far no emerald ash borer,” he said. “I have caught 25 or 30 beetles this morning. No bad beetles, just other wood-boring beetles. All are native.”

He didn’t see anything that has him worried about invasive pests.

How to help

Homeowners should take a proactive strategy.

“They should keep an eye on their trees,” Mr. Kroon said. “There are a lot of landscape problems that face trees.”

Homeowners should look for defoliation problems. A tree that drops leaves earlier in the summer before temperatures cool down likely has a problem, he said.

The emerald ash borer will leave D-shaped exit holes about 1/8 inch in diameter.

Once emerald ash borers have been documented within 15 miles, an insecticide treatment plan for healthy trees is recommended. Mr. Kroon also said that as trees age, they should be replaced with other species.

Homeowners can call the Department of Agriculture at (302) 698-4500 for advice and help in managing their trees.

“We do sick tree calls,” he said.

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