Gypsy Moth Update
Mid-June 2008

-Submitted by Mike Kay, Forester
Maryland Forest Service

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Forecasts for 2008, based on fall 2007 egg mass counts, predicated a severe outbreak of gypsy moth in Frederick County affecting nearly 43,000 acres of forests.  This represents nearly 30% of our forest land base in the county!  With this in mind the Maryland Department of Agriculture ramped up its yearly suppression program spraying nearly 23,000 acres of forest in the county.  A private “supplemental” program was also launched where private landowners paid 60% of the cost of suppression and 40% was cost shared from funds earmarked by the Frederick County Commissioners.  This supplemental program resulted in the spraying of nearly 9,000 acres.  The supplemental program was developed and administered by a diverse group of partners known as the Frederick County Gypsy Moth Task Force.  In addition, the Federal Government sprayed much of their susceptible forest land in Catoctin National Park and along the C&O Canal and Monocacy National Battlefields.

Spraying for gypsy moth on May 18, 2008

Most gypsy moth populations are entering into the final stages of their larval development as this is being written on June 19, 2008.  The larvae are entering a transformational “pupal” state for a few weeks then they will emerge as adults, mate, lay their eggs then die.  Once the larval stage is past, the threat of defoliation is over since adult gypsy moth does not feed.

A section of forest near Thurmont that was defoliated by gypsy moth.
Photo taken June 16, 2008.

A nearby property that was spayed with Confirm
during the supplemental program.

By late summer we will be better able to assess the damage inflicted on our forests when the Maryland Department of Agriculture conducts its aerial surveys; and, determine the gypsy moth threat for 2009 by counting newly laid egg masses.  From my general observations, it appears that the widespread spraying initiative combined with environmental factors has helped us avoid widespread destruction by this damaging insect.  I have recently seen signs that naturally occurring disease pathogens are impacting gypsy moth such as the NPV virus and the bacterium Entomophaga maimaiga.  These pathogens are more active when we experience cool, wet weather during the spring and the gypsy moth populations are high which certainly the case was during 2008.

A late season larvae getting ready to pupate right, next to
a gypsy moth that has died from the NPV Virus left.

The Gypsy Moth Task Force will be meeting in Mid-July to critique the supplemental program and to develop a report that will be distributed to the County Commissioners and other State and Federal officials.  Our hope is that we can maintain the necessary resources to enable gypsy moth control should a damaging population arise again.