Friday, May 13, 2016

Gypsy moth infestations


a freshly hatched gypsy moth caterpillar

Growing up in Pennsylvania in the 1980s I saw years when the leaves came out on the trees in May and were gone by middle of June.  From a distance, the rolling, forested hills would look like they had in March – all grays and browns.  Up close, hiking in the woods you would hear a constant hiss of frass falling from the gypsy moth caterpillars above - like a dry rain.  

The first year or two trees would re-leaf by July, but if the moths persisted trees would begin to die.

Here in Rhode Island, flocks of grackles – accompanied by a few cuckoos – spent a couple of weeks last summer in our woods at the height of the caterpillar season.  (The two species have found ways to deal with spiny caterpillars like the gypsy moth.  The yellow-billed cuckoo can discard its stomach lining once it has ruined it with the caterpillar's defensive spines; the grackles seem to take the more direct approach of trying to beat the spines off by smacking them against a tree branch.)  

But there is only so much they can do, and at the end of summer there were hundreds of tawny egg patches - proof that plenty of moths had evaded predation.


Now the trees are coming into leaf, and tiny newly hatched caterpillars are on the move.  That's what has me recalling the deforestation of years past.  Maybe it will turn out to be a localized outbreak and the cuckoos and grackles will come back with friends to share the bounty.  Or maybe it will be like the bad old days, where defoliation stretched mile after mile.

with ballpoint pen, for scale

3 comments:

  1. yeah, i've seen the patches on the trees and the tiny little caterpillars everywhere. but the good news is that, unlike last spring, we've had a cooler, wetter spring this year, which means that the fungus that kills the caterpillars should be much more effective that it was last year. it's that fungus that has kept them in check for years now. last spring was very dry, and the fungus could not proliferate.

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