Invasion of the Emerald Ash Borer with Sonja

Johanson

by Laurie Ann Knowles

In early June of 2002 an unfamiliar iridescent green beetle was delivered to the University of Michigan Department of Entomology, prompting a team of entomologists to visit a stand of unnaturally declining ash trees in the City of Detroit. State regulatory officials quickly joined the university naturalists to determine the scope of the problem. Over the following weeks, all concerned parties were surprised and staggered by the level of Emerald Ash Borer (EAB) infestation in the southern Michigan area. By mid-July the Michigan Department of Agriculture imposed a statewide quarantine regulating the movement of ash nursery trees, logs and related products. In October of 2003 the US Department of Agriculture established a nationwide quarantine of a similar nature. Unfortunately, the beetles, which probably arrived (as many as ten years prior to their discovery) in packing crates from Asia, have continued to spread unabated.

The challenge presented by the EAB is — in one important way — the same as that posed by gum disease. Just like a person suffering from the onset of periodontitis, a tree in the early stages of infestation by this bright metallic green jewel beetle will show very few symptoms. Unlike gum disease however, the ash borer, once established in an area of ash trees, spreads quickly from host to host. A second similarity is that both of these problems are best addressed preemptively, by practicing good oral hygiene to keep your teeth healthy and by the use of insecticide treatments to protect high-value trees, such as large shade trees, historic trees and trees specifically valued by homeowners.

First detected in Maine in 2018, the EAB will slowly migrate across the entire state. It is impossible to protect ash trees in the forest — the EAB does not have local predators and treating a forest with insecticides is completely unworkable. It will not however completely devastate the genus; most of the large ash trees will be destroyed but ashes have the ability to stumpsprout. The root systems produce shoots and from them trees will regrow. But the EAB attacks trees about 6” in diameter or larger so the cycle of destruction and regrowth will likely continue indefinitely. Also, since mature ash trees produce abundant seeds, saving trees at people’s residences will be key in helping the species regenerate. Eventually scientists hope to introduce natural predators to help control EAB populations, but it is expected to take roughly twenty years for those controls to become established.

About 10% of trees in the Great Northern Forest are ash species of one sort or another. Here in western Maine our forests contain White Ash, Green Ash and Black Ash in the swamps (Black Ash is the wood used for basketry by Indigenous peoples). Green and white ash are large, deciduous, wind-pollinated trees which can reach 70-100 feet at maturity. These attractive shade trees can be identified by their tightly furrowed bark, pinnately compound (featherlike) leaves, bright yellow autumn foliage and winged seeds (samaras) on the female trees. Locally, an impressive example of stately ash trees greets drivers at the intersection of the

Intervale Road and Route 26 just as they enter downtown Bethel from the south. Looking to the right travelers will see the long white fence at the Shepley Farm offset by an impressive row of 60-year old male ash trees. Currently, the Shepleys are consulting with their neighbor Sonja Johanson, who works as the lead horticulturist for Nadeau Development in Woodstock, about options to protect their trees from infestation.

Sonja was a founding board member of the Massachusetts Master Gardener Association, a not-for-profit organization which provides public outreach and education by trained horticultural volunteers. She served for five years as the Master Gardener Training Class Coordinator, then went on to hold a variety of positions at MMGA, including Education Coordinator, Outreach/Volunteer Coordinator and President.

Sonja, who grew up in Auburn and studied Ecology at the College of the Atlantic in Bar Harbor has worked with Mike Nadeau for the past three years. Preventative treatment options for the EAB include pesticide spraying and/or soil drenching - but trunk injection, which requires training in the use of specialized equipment, is safest for both people and the wider environment. Trunk injections affect only the trees being treated, and do not risk being spread through air, water, or soil. Commercial landscapers like Sonja, who specialize in this type of tree care, must be certified by the Maine Board of Pesticide Control and licensed as a Master Applicator with a specialty in ornamental plants and trees.

The ash borer has a look-alike — the tiger beetle. Anyone who finds a beetle can send a photo or the bug itself to the state’s offices for identification. v