Gypsy Moth Suppression - 2011

The cool damp conditions we are experiencing in 2011 should promote the growth of various diseases that will affect trees, but it should not encourage insect outbreaks, especially in the lepidopterous "moth and butterfly" group (of which gypsy moth is a prominent member).

Gypsy moth numbers saw a steep decline after 2009, and if they behave like historical models, there should be eight to 10 down years following the three up years we experienced in 2007, 2008 and 2009.

There were very few viable egg masses deposited in Frederick County last summer, and gypsy moth egg mass counts are low. As a result, there will not be much gypsy moth presence this spring. Although no counting of Eastern tent caterpillars, forest tent caterpillars or oak span worms are taken, these insects should be on the low side also, based on the weather conditions.

A review of the 2009 Supplemental Gypsy Moth Program

The Frederick County Gypsy Moth task force met during the fall of 2008 and determined that a supplemental gypsy moth suppression program would again be needed in 2009 given the expected levels of infestation throughout the county. Parkton Woodland Services was once again retained to provide administrative support and, the task force submitted bid requests to numerous spray contractors. Helicopter Applicators provided the successful bid and were chosen as the spray contractor.

To publicize this program the Task Force sent out individual mailings to previous year’s participants, submitted articles to local newspapers, and held a gypsy moth informational meeting at the C. Burr Artz Library in Frederick City on December 4, 2008.

The failing economy of 2008 – 2009 had a fairly significant impact on this program. Given budget constraints Frederick County was unable to offer monetary assistance to provide cost sharing. In addition, the State of Maryland had to drop some of their anticipated spray blocks due to reduced funding levels thereby increasing participation in the supplemental program in some cases. In addition, many private individuals cited poor economic conditions as reason for not participating in the 2009 program.

Spraying for the Supplemental Program began on May 12, and concluded on June 1, 2009. In total, nearly 300 landowners participated in this program treating some 5,400 acres. All of these properties were sprayed with the insecticide Confirm at 3.5 oz/acre. The spring and summer of 2009 was characterized by cool, rainy weather. These environmental conditions benefit the naturally occurring virus and fungus that suppress gypsy moth numbers. The result of the public and private spray programs along with the prevailing climatic conditions is that that gypsy moth populations had declined significantly without causing much defoliation.

These ground observations were confirmed after The Maryland Department of Agriculture, Forest Pest Management Section conducted its summer flight to determine levels of defoliation and noted no significant defoliation in any section of the county. In addition, the Forest Pest Management Section is in the midst of their gypsy moth egg mass surveys and reports that no significant populations exist to warrant developing a spray block in 2010. This survey is not yet complete so this might change. For now it appears that the gypsy moth populations have crashed and it looks like no significant spaying will be necessary in 2010 or the foreseeable future.

Special thanks go out to those private citizens who assisted with this effort especially members of the Gypsy Moth Task force many of which spent significant time and effort on this project with no monetary gain. Also thanks go out to the local jurisdictions who assisted with this program especially Frederick County, legislators who helped acquire diminishing funds for this work, and those individuals in the MD Department of Agriculture, MD Department of Natural Resources, Parkton Woodland Services, and Helicopter Applicators that assisted with the spray effort.

Mike Kay

The maps below show the results of spraying on defoliation in 2008 for Frederick County. Note the lack of overlap between the spray areas and deloiation areas (maps courtesy of Frederick County Geographic Information Systems (GIS)).

    • View map 1 comparing spray blocks and defoliation for Frederick County 2008
    • Northern Frederick County
    • View map 2 comparing spray blocks and defoliation for Frederick County 2008
    • Central Frederick County
    • View map 3 comparing spray blocks and defoliation for Frederick County 2008
    • Southern Frederick County
    • Also, the Frederick News-Post has recently featured an article entitled County gypsy moth spraying likely to face budget squeeze that addresses concerns about future spraying by the county.

In 2008, gypsy moth infestations in many forested areas of Frederick County were severe enough to potentially defoliate thousands of acres of forest. High tree mortality can result from gypsy moth defoliation two or more years in a row or when other stresses to the forests are present such as drought. In 2008, thousands of acres of Frederick Forest are expected to be defoliated, unless treated. With an estimated one million acres devastation since 1980 state lawmakers have been studying the problem. "It literally looks like a war zone once they come through," said American Joe Miedusiewski, a lobbyist for the Maryland Arborist Association (Washington Post, Moths Munch Trees, 3/21/2008).

Gypsy moths, native to parts of Europe, Asia and Africa, were brought to the U.S. for a breeding experiment to produce a more robust silk worm. After their accidental release in the United States in the 1860’s they have proliferated in the absence of the natural controls present in their native habitat. Gypsy moth larvae (caterpillars) have voracious appetites and thrive on the hardwood forests of our area, with oaks being their preferred diet.

Pictured below are Gypsy moth larvae emerging from the egg mass (left) and an older Gypsy moth larvae showing five pairs of raised blue spots and six pairs of raised brick-red spots (right).

On November 3, 2007 the Frederick County Forestry Board conducted a workshop at Cunningham Falls to educate property owners of the anticipated spring time infestation of gypsy moths and the potential defoliation of Frederick forests. The workshop resulted in a follow-up meeting where concerned property owners discussed alternative actions to combat the problem. Six attendees have offered to serve as a 'task force' to act as an interface with spray applicators and the property owners. The Frederick County MD Gypsy Moth Task Force has also been successful in securing governmental support for the suppression program.