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Winter Moth

Professional Winter Moth Control in Maine

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winter-moth-preventionFollowing last year’s relatively mild winter – specifically during December when winter moths typically emerge from the ground to mate and lay eggs – tree experts are bracing for another strong wave of destructive winter moth activity later this fall and early winter. This makes winter moth control now an imperitive.

In the past, researchers have noted higher levels of tree damage in the spring following mild winters. Notably, the spring of 2013 resulted in heavy damage following a mild December 2012, while the damage reported in 2014 and 2015 was less after freezing temperatures and snow blanketed the region during the previous December. The Maine Forest Service projects that high levels of brown tail moth caterpillars will continue to appear along coastal Maine through 2017.

Leading the Crusade, One Maine Town Goes on the Offensive

In Cape Elizabeth earlier this year, the town council took steps to potentially minimize the damage that these invasive species can do by creating a $50,000 fund “…to treat, remove or replace trees impacted by the insect.”

Cape Elizabeth’s Town Manager Mike McGovern expressed concerns about how an uncontrolled winter moth infestation could impact thousands of trees, located on both residential and town-owned public properties in a July 28, 2016 Current news article ‘It’s Cape vs. Moths’.

“This could be something that could cost us hundreds of thousands of dollars in the next few years,” said McGovern. Having funds on hand “would enable the tree warden to address the immediate hazards.”

A Birds-Eye View of Winter Moth Damage in Cumberland County

Following their arrival in Massachusetts in the early 2000s, winter moths (Operophtera brumata) have since spread into much of Rhode Island, parts of Connecticut, and have established several colonies along the coast of Maine.

Although difficult to predict exactly where a winter moth infestation will occur, recent aerial surveys by the Maine Forest Service have found areas of heavy defoliation in several coastal towns, including Cape Elizabeth, Scarborough, Harpswell, Chebeague Island and Peaks Island. Additionally, damage from winter moth infestations have been reported from Kittery to Bar Harbor over the last several years.

The Maine Forest Service is also calling on citizen scientists to help gather information about where winter moths are being observed throughout the state. In 2015, the forest service collected more than 700 entries through an online survey located on the Maine Forest Service website.

Another citizen science effort, this time coordinated by the Gulf of Maine Research Institute, asks “Where in Maine is the Winter Moth?” through its online Vital Signs program, Mission: Winter Moth.

Many deciduous plants are hosts for the winter moth. Specifically, here in Maine it appears that oak, maple, basswood, white elm, crabapples, apple, blueberry, and cherry trees are most often at risk.

Winter Moth Control: A Professional Strategy Works Best

Unlike most other defoliator species, winter month caterpillars do their damage in the spring – when hardwood trees such as oak and maple are just beginning to bud. After they have had their fill, the caterpillars drop to the ground and spend the summer and fall buried in underground cocoons.

Once in the soil, cocoons can sometimes be inadvertently transported by moving perennial plants and shrubs from one location to another. Caterpillars can also be transported by cars and boats during the spring.

Winter moths typically emerge from their pupal state (cocoons) in late November to January. After mating, female winter moths (who are unable to fly) primarily lay their eggs on the trunks and lower branches of trees. The eggs are initially green and located on bark near the base of the tree, under lichen and along large branches. Soon after, the eggs become more visible, turning light orange. It is during this time that professional winter moth control services can be most effective.

Prevention and Treatment Success is Time and Temperature Sensitive

When exposed, winter moth eggs can be treated with horticultural oil sprays that suffocate the egg. Commercial spray applicators, such as the trained professionals at Lucas Tree Experts, can also add certain chemical insecticides to the oil spray in order to kill any newly hatched caterpillars that were not affected by the oil treatment alone.

Mixing compounds is a practice that is best left to the professional licensed applicator and not something that homeowners should attempt on their own. Not only could doing so cause a dangerous reaction to the individual, but mixing solutions that were not meant to be combined can also cause serious damage to plants and the surrounding environment.

Temperature also plays a critical role in the efficacy of oil sprays. Professional winter moth control experts typically will avoid applying oils when sub-freezing temperatures are expected 24-48 hours following application. Ideally, temperatures should remain above 45° F during that time.

Another method of limiting the ability of adult female moths from climbing up trees to mate and lay eggs is by wrapping a band of sticky material around the trunk of the tree. This may or may not be an effective control for winter moth infestation as caterpillars are known to often “balloon” from tree to tree (bypassing the trunks altogether). In addition, if/when the sticky band becomes saturated with captured moths, others will simply climb over them and continue on up the tree.

Long-Term Bio Controls Will Take Time

In an effort to take back their forests from this voracious defoliator, our Massachusetts neighbors have been releasing a specific type of fly (Cyzenis albicans) since 2005 that seeks out and destroys young moths. The promising results from the Massachusetts program, modeled after a similar program launched in the 1950’s in Nova Scotia and British Columbia, has led Maine to undertake similar actions.

With funding from the federal government, the Maine Forest Service released thousands of the parasitic flies – which are only known to attack winter moth hosts – in Cape Elizabeth and Harpswell in 2013, Kittery Point, Harpswell and Vinalhaven in 2014, and Cape Elizabeth and Peaks Island in 2015.

According to reports from the time, the effects of parasitic flies that were first introduced in the Nova Scotia project in 1954 did not begin to show positive results until 1959. Similarly, Massachusetts announced its success against winter moth infestations in 2011, five years after the program begun.

Depend on Lucas Tree Experts For Professional Winter Moth Control

The tree service experts at Lucas Tree are ready today to help protect your trees from winter moth infestation. Lucas’ certified arborists are trained in professional winter moth control, and will work with you to develop a prevention and/or treatment plan specific to your property.

Contact Lucas Tree today for more information about winter moth control and prevention planning.


University of Maine Cooperative Extension winter moth fact sheet