Saturday, December 19, 2009

Winter Moths

When I first saw the mass of moths attracted to the lights beside the garage I thought it was an interesting phenomenon.

Then I heard someone say they were winter moths.  That made me think they would make a good blog subject.  I had read something about winter moths in Bernd Heinrich's Winter World.  So I started doing some research.  An insect that flies during the winter, they must have some really cool adaptations.

Then I found out that these winter moths are Operophtera brumata, an invasive species.    That's not so cool.

Winter moths are a European species introduced to this continent last century.  They started showing up in New England early this century and are already becoming a major problem.  Winter moth males fly during November to as late as January, the females are wingless and wait on trees and shrubs for the males to find them.  They lay their eggs under the bark.

In the spring the eggs hatch and the larvae begin feeding on the unopened buds.  As the untouched buds start to open the larvae will move to nearby branches or leaves and continue munching.  They can easily defoliate whole trees, with a preference for fruit trees.  In springs like our last spring with cool weather and delayed bud opening the damage can be intense. 

Not surprisingly the defoliation process is harmful to trees, it can even be fatal if repeated over several years.  On the plus side the spring migrating birds (especially warblers) have plenty to eat at a critical time in their life cycle.  They subsequently arrive relatively plump and ready to go on their nesting grounds.

Our street tree, an American Linden (or Basswood), was heavily infested this past year.  With this massive fall flight I predict it will be heavily infested again this year.  I'm not going to do anything to fight the moths (winter moths are hard to control and professionals should be consulted.  I was unable to find information on an organic option that actually works) at least in part because I think that is the wrong tree for that spot and that spot is really, really bad (directly in front of our front door so people who park on the street have to go around the tree to get to our front walk).  If the tree doesn't survive I'll quietly replace it with something a little more appropriate to the spot and off center from our front door.  Probably not a fruit tree, though.

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