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Winter Moth Survey Update 2016

Milan Zubrik, Forest Research Institute Slovakia

Winter Moth Adult

The winter moth flight came and went this fall, and numbers were so low, you might not have noticed them at all…

The winter moth (Operophtera brumata) is an invasive species first discovered in Massachusetts in the 1990s. Winter moth caterpillars are highly efficient tree defoliators, often stripping the leaves of oaks, maples and other hardwood trees down to lacy skeletons. Adult flight typically begins in November and will continue through late December or early January.  During this time, female winter moths can lay up to 150 eggs each, which will hatch into hungry caterpillars in spring.

Whereas our annual winter moth survey typically gets over a thousand responses each year, we only received 75 responses between November 2016 and January 2017. The low number of responses is strongly linked to the fact that winter moth adult populations were down significantly this year.  But this decrease in activity was not totally unexpected.  Last year, winter moth populations fell due to some unusual weather that encouraged the caterpillars to hatch before tree buds opened, leaving them without a source of food. Additionally, the parasitic fly Cyzenis albicans has been establishing at release sites throughout eastern Massachusetts and is also contributing to reductions in winter moth populations.

Winter Moth Caterpillar

However, that doesn’t mean that winter moth is going away any time soon.  Even if winter moth populations are low in spring of 2017, they can still rebound.  For homeowners who want to treat their trees for winter moths please see this winter moth fact sheet for more information about dealing with this pest.


Photo credits: Milan Zubrik, Forest Research Institute Slovakia,

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