Silent Killers Stalk Backyard Giants

You may think you live in a safe neighborhood, but if you were a tree you'd think differently. Tree thugs are on the loose.

Experts know most of the suspects, have their photos, and can even name their general whereabouts. But without involvement from tree owners, there is a limit to how much the experts can do.

Case in point: Emerald ash borer (EAB) is confirmed in 38 Connecticut towns, now pushing east into Clinton, Durham, and Cromwell. According to the Connecticut Agricultural Experiment Station (CAES), which monitors plant disease and insect threats throughout the state, ash trees make up 4- to 15 percent of the state's green canopy, depending on the locale. EAB was first discovered in New Haven County in 2012, and, according to Dr. Clare Rutledge at CAES, parasitizing wasps were released in 2013. Woodpeckers are their only other natural predator in this area.

But while we wait for wasps to control the EAB population, this copper green borer beetle, less than ½-inch long, can kill every ash in its path. Ask anyone from Michigan, Ohio, or Pennsylvania.

Adam Cervin, a licensed arborist with Care of Trees who works in eastern Connecticut, says that when an insect is confirmed in that broad a territory, "We can assume EAB is present throughout the state. It just hasn't been confirmed yet."

The good news, he says, is that mature ash trees can survive EAB with preventive treatment.

"The rule of thumb is to treat otherwise-healthy ash trees when EAB has been discovered within 15 miles," says Cervin.

There are three approaches to treatment, which he says have a high success rate if applied in time. Cervin points out that the expense of treatment is usually less than a quarter of the expense of removing a mature tree.

While EAB is currently making headlines, Cervin says it is hardly the only emerging threat to trees. He is concerned about an increase in Phytophthora bleeding canker that can weaken and eventually kill stately beech trees that grace the lawns of homes and parks.

"After the bleeding canker gets established, other pathogens and insects move in," he says. Both American and European "copper" beeches are affected.

He is also concerned that other insects in nearby states will soon arrive.

"Winter moths are defoliating and disfiguring trees in Massachusetts and Cape Cod," he says. "Gall wasps are doing damage on Long Island and the Cape."

In reality, trees are always subject to a variety of threats, but in many cases, preventive measures can ward off the worst outcomes.

Here are three steps you can take:

First, do a tree inventory. Once you have an accurate list, you can be alert for threats to species on your property. There are many good resources for tree identification. My favorite entry-level approach to tree identification is called "What Tree Is That?" a guide offered by the Arbor Day Foundation (www.arborday.org) both in print and as a phone app.

Second, take advantage of free identification, update, and diagnostic services offered by CAES and UConn. Call CAES in New Haven (877-855-2237) or Windsor (860-683-4977). Follow alerts from CAES on Facebook (www.facebook.com/CT.CAES) or Twitter. Visit its website, www.ct.gov/caes.

UConn Extension offices in Hamden, Haddam, and Norwich will also help identify trees and will accept samples for diagnosis. Call the UConn Home & Garden Center at 877-486-6271 for more information.

Third, use licensed arborists to maintain your trees. They are trained to do on-site identification and diagnosis and must pass exams to maintain their status. The Connecticut Tree Protective Association (www.ctpa.org) provides links to licensed arborists, as well as a number of helpful resources.

A mature tree offers a lot of environmental and economic value. In fact, some sources say that a tree has to be 20 or 30 years old before it reaches the peak of its beneficial functions. As Cervin points out, however, "You're always better off doing things preventively. It's really a challenge to turn it around once an insect or pathogen has shown up."

Kathy Connolly is a garden coach, writer, and speaker from Old Saybrook. You can email her at kathy@speakingoflandscapes.com. Visit her website at www.speakingoflandscapes.com.

You're unlikely to see the Emerald Ash Borer directly, but its damage is easy to spot on the bark of ash trees. It leaves -inch holes, often D-shaped, in the bark. Underneath the hole, their tunnels are highly visible in the cambium layer.
You're unlikely to see the Emerald Ash Borer directly, but its damage is easy to spot on the bark of ash trees. It leaves -inch holes, often D-shaped, in the bark. Underneath the hole, their tunnels are highly visible in the cambium layer.

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