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Is it snowing outside? No, it’s winter moths! December 6, 2012

Posted by bsciencecenter in Science.
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Is it snowing outside? No, it’s winter moths! The winter moth, an invasive insect originally from Europe, was introduced into the United States through Canada and Nova Scotia before the 1950’s. You can see these moths throughout eastern Massachusetts in huge numbers.


The adult winter moths (Operophtera brumata) emerge from the ground in November or December, but only the male is able to fly. The female climbs to the base of a tree or building and attracts the male through the pheromone (scent) that she gives off. After mating, the female lays a cluster of approximately 150 eggs under tree bark or in tree crevices, and her life is now over. In March or April the eggs hatch into a smooth green inchworm with a narrow white-stripe running lengthwise on each side of the body. The caterpillar spins a strand of silk, which, with the help of air currents, takes it into tree canopies in a dispersal method known as “ballooning”.


Once there, the damage to the tree begins as the caterpillars work their way into the tree buds and leaves to feed. In Massachusetts, the tree species frequently affected are maple, oak, ash, as well as fruits producers such as apple, crabapple, and blueberry. Winter moth caterpillars can also drop from trees to nearby ornamental shrubs such as roses. When feeding ends in mid-June the caterpillars migrate into the soil to pupate and emerge as moths.



What can we do to control this moth?

No natural controls are known to be present in Massachusetts, but researchers at the University of Massachusetts in Amherst are actively collecting and rearing a parasitic fly (Cyzenis albicans) that was very effective at controlling winter moth outbreaks in eastern Canada and the Pacific Northwest. Unfortunately, effective biological control ismany years away.

Info c/o UMass

Check out these links for more winter moth information:






1. J.J. - December 6, 2012

Now I know what’s eating my ash and maple trees. Thanks.

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