The general collapse occurred as a result of the extremely unseasonal rainy weather that the whole of Pennsylvania experienced during late May and June. On three separate occasions, stationary fronts parked themselves over the Ohio valley and poured rain on us for a whole week. These were very favorable conditions for the pathogenic fungus, Entomophaga maimaiga, to grow from strength to strength until it killed even strong, late-stage caterpillars all over the county.
Please Report any Flying Moths
Even though it’s pretty certain that we have had a total gypsy moth population collapse, there is still a tiny chance that small residual populations survived in some parts of the county. The best indicator that this has happened is the presence of flying brown gypsy moth males and white non-flying females present on trees. If you do see any adult gypsy moths, please report them online on the county’s gypsy moth web site (www.co.centre.pa.us/gypsymoth).
As always, negative findings (no gypsy moth adults seen) are very important, as a reported absence of gypsy moths is a significant event in itself. (A negative report only takes 10 seconds to make; a positive report takes less than 1 minute.)
Identification Tip: Gypsy moth is one of the few moth species in N. America which flies during the day. Another telltale sign that it’s a gypsy moth is its zigzag flight path as it tracks the scent of the pheromone produced by the female. See the web site for pictures of male and female moths.
(Edited from the Centre County Gypsy Moth Coordinator - Gypsy Moth News, July 2009)