Turn exterior lights off when the moths come out

Leaves return to caterpillar-eaten trees

Local arborists caution against cutting down infested trees
By Susan Mustapich | Jul 09, 2019
Courtesy of: Maine Forestry Service Browntail moth caterpillars have defoliated oaks and other trees in Camden, Rockport and Lincolnville, but the leaves are reported to be coming back.

CAMDEN — Small, spring-like leaves coming out on oak trees defoliated by browntail moth caterpillars are a sign of resiliency against the invasive pest that hit hard in numerous Knox County towns this spring and early summer.

Douglas N. Johnson, co-owner of TREEKEEPERS LLC. with his wife, Nancy Caudle-Johnson, has noticed the trees refoliating along the south end of Lake Megunticook and other areas. Johnson said he "was elated seeing the leaves come back on the trees. Now people will have shade."

The rainfall this year has also reduced the stress on the trees, Caudle-Johnson pointed out.

Tom Schmeelk of the Maine Forest Service said July 9 that "the oak trees are leafing out again" at a site he has visited in Whitefield, where the trees "were 99 percent defoliated." He said it is the trees' typical response to defoliation "to pump out another set of leaves."

He concurs that the rainfall has been beneficial, "Not having a drought has also helped the leaves grow," Schmeelk said.

While it's odd to see the small, light green leaves on oak trees next to other trees with full-sized leaves, it's a good sign, according to Johnson, because it means there is no need to cut trees down in order to deal with browntail moth caterpillars.

Johnson is concerned that earlier this year other arborists cut down trees infested with the caterpillars, when there was no need to do this.

Nancy Caudle-Johnson said this spring TREEKEEPERS LLC was offering to its clients up and down the coast an organic product that is injected into the tree and drawn up into the leaves. She said this treatment appears to rid the trees of caterpillars, and that the treated trees did not get defoliated. She added that it is necessary to wait longer to determine the results.

The product is effective only if applied when the leaves are emerging, Caudle-Johnson said. TREEKEEPERS first inspects the trees. If the infestation is reachable by ladder, which applies to fruit trees, it can be removed by pruning, she said. The organic pesticide is used only for infestations that are high up in trees, such as oaks. The trees must be measured, as the amount of the product is based on the size and species of the tree.

She said the company has received an average of 10 calls a day, and is still receiving them. Because of the demands of helping existing clients, the company has mainly referred callers to the Maine Forestry Service's 211 telephone help line, and has heard from some people that that has been helpful.

Caudle-Johnson pointed out that Maine licensing for pesticide application, even organic products, protects the public because it requires training and monitoring. She said the licensing, training, continuing education and record-keeping required creates obstacles and "is hugely time consuming, but we do this to save the trees."  If arborists apply pesticides illegally, it's bad for everyone, she said.

She cautions property owners to make sure that they work only with Maine-licensed arborists who have the required pesticide licenses. The company has to have a master applicator, which is a separate license, and anyone on the crew who does the injections has to have an operator license. Pesticide license exams are more expensive than arborist licenses, Caudle-Johnson pointed out, and also require continuing education to keep them valid. Record-keeping includes maintaining a log of the date, location and product for each application, and the logs have to be turned in to the state each year. The state also has a notification registry, and those on the registry, located with 250 feet of a property where a pesticide is applied, must be notified in advance of an application, she said.

Despite everything involved, the organic pesticide application is much less costly than cutting a tree down, Caudle-Johnson said. Additional costs in taking down trees include the loss of habitat for birds and wildlife, the loss of environmental benefits, including pollution absorption, which purifies the air, and cooling shade, which counteracts heat produced by buildings and pavement, and can save homeowners energy costs, according to Project Canopy of the Maine Forestry Service.

The future of the browntail moth infestation in Knox County is still unknown, according to Schmeelk. While research sites monitored by Dr. Eleanor Groden at UMaine Orono have seen some localized population collapses of the browntail moth caterpillar because of an entomohaga fungus that kills the caterpillars and grows well in wet weather, "We are on hold, because we need to see if the moths are going to replenish that population," he said.

That leads to the next step in battling browntail moths, which is keeping exterior lights turned off when the moths emerge in August, Johnson said. Because browntail moth caterpillars like oaks, beech, willows and fruit trees best, it is helpful not to attach outdoor lighting to these trees. Johnson said he can see more infestation and damage in trees that are near outdoor lighting, or where there is lighting on the trees themselves.

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