Saving Your Ash
April 23rd, 2012
Mechanicsburg arborist Bob Carey was scouting a client’s yard for pests last August behind Wormleysburg’s Harrisburg Academy when he noticed an unusual shiny green bug.
Emerald ash borer adult.
“I saw this beetle light on one her plants,” says Carey. “I captured it and said, ‘This sure looks like an emerald ash borer.”
Turns out it was, and with the discovery came the crawling reality that this dreaded, highly destructive tree-killing bug has definitely arrived in the Harrisburg area.
The discovery is a game-changer for the future of the region’s ash trees – both in home landscapes and especially in the wild.
We now go from “watchful waiting” to a decision on whether or not to spend money on ash-protecting chemicals.
First found in Michigan in 2002 as a hitch-hiking invader on wooden packing material from China, the emerald ash borer so far has wiped out an estimated 40 million ash trees in five states.
It’s been moving relentlessly eastward since, arriving in Pennsylvania’s Butler County in June 2007.
The state Department of Agriculture tried to quarantine the pest and put out pleas for people to avoid moving ash firewood.
It didn’t work.
An emerald ash borer trap.
By last year, traps baited with manuka oil caught Agrilus planipennis in 23 counties. The traps are those purple kite-like contraptions that you may have seen hanging along roadsides.
“We know how devastating this pest has been in other parts of the country,” says Carey. “It has the capability of effecting the same kind of damage here.”
The real problem isn’t the adult beetle, which is a hard-shelled bug about the size of an elongated housefly with a shiny, metallic-green back and two big, black eyes.
The adults do minor leaf damage while they fly around, mate and lay eggs on ash trees from June into early July.
The “kids” are responsible for the real damage.
Once the eggs hatch, the skinny, cream-colored larvae bore into ash wood and feed on the tree’s xylem and phloem – the parts that move water and nutrients up and down the tree.
Within one to three years, even a few borers can kill an otherwise healthy ash tree.
“This is a very aggressive pest,” says Eric Vorodi, a certified arborist and owner of About Trees Consulting in Boiling Springs.
If it’s any consolation, at least EABs – as they’re known in the entomology world – go after only species in the Fraxinus, or ash, genus.
That means if you have a mountain-ash, you’re off the hook since that one is an ash look-alike that’s really a type of Sorbus.
Which brings us to the matter of what to do if you’ve got ash trees.
“It boils down to two options, with one of them giving you three more options,” says Vorodi. “One is to wait and see and take your chances. The other is to treat proactively. Once you get (emerald ash borers), though, the chances of controlling them are not good.”
Like most human ailments, the key is catching an infestation early – or preventing it in the first place.
An ash tree that's already lost most of its canopy and is putting out last-gasp new scrubby growth from the trunks.
Tree experts say if you wait until an ash has suffered 30 to 50 percent damage, it’s usually too late. Even if you stop further damage, is what you have left worth saving?
“This isn’t even on people’s radar yet and probably won’t be until we see chainsaws taking down trees,” Vorodi says. “I don’t think most people are going to notice even 30 percent damage.”
Early signs of damage include a dieback of branches in the tree’s upper canopy along with new scrubby growth emerging from the tree’s trunk. Woodpeckers also may show up in search of a tasty larval meal, and you may notice vertical slits in the bark.
But the telltale sign is the D-shaped exit hole that a young EAB adult makes as it leaves the tree. The holes are about the size of a pencil eraser.
Even more elemental, though, is identifying and monitoring any ash trees on your property.
“If you’re a homeowner and have an ash you’re attached to or consider it to be an important element in the landscape, there’s no reason to lose it,” says Carey.
If you really don’t want to risk it, Carey suggests soaking the ground around the tree once a year in spring (i.e. now) or fall with imidacloprid.
Available in garden centers and home stores, one treatment per year controls an estimated 60 to 70 percent of borers, says Vorodi. A commonly available brand is Bayer Advanced Garden Tree and Shrub Insect Control.
Homeowners also can hire a tree or pest-control company to apply the same chemical or two other choices that only pros can apply.
The tell-tale D-shaped exit hole of an emerald ash borer.
One is a spray of dinotefuran that’s usually applied to the bark. Like imidacloprid, it controls about 60 to 70 percent of borers for a year.
The other is emamectin, which gets injected into the trunk and gives nearly 100 percent control for 2 years, according to Vorodi.
Emamectin injections are more labor-intensive and about twice as expensive per treatment, but since they last twice as long and are considered to be most effective, it’s probably the best long-run option for people who want some ashy peace of mind.
Bottom line: “How much time and money do you want to spend trying to save your particular tree?” says Carey. “You have to decide which ones you want to hold hands with.”
Additional sources to help fend off the emerald ash borer:
* For detailed information and frequently asked questions: www.paemeraldashborer.psu.edu or www.emeraldashborer.info or www.agriculture.state.pa.us and enter “emerald ash borer” in the search box.
* To identify an emerald ash borer and its damage: http://ento.psu.edu/extension/trees-shrubs/emerald-ash-borer/factsheets/EAB1215.pdf/view.
* To tell an ash tree apart from similar-looking species: http://ento.psu.edu/extension/trees-shrubs/emerald-ash-borer/factsheets/EAB2942.pdf/view.
* Options for treating for emerald ash borer: www.emeraldashborer.info/files/Multistate_EAB_Insecticide_Fact_Sheet.pdf