The Virginia Department of Forestry (DOF) and the Virginia Department of Agriculture and Consumer Services (VDACS) are joining forest health professionals to monitor the invasive spongy moth (formerly known as the Gypsy Moth).
Long established in Virginia, the caterpillar with a voracious appetite favors oak trees but will also feed on many types of hardwoods. In areas with large infestations, the caterpillars can strip entire mountainsides of foliage.
In 2024, the most severe damage has been observed in the Northern Shenandoah Valley and the mountains west of Harrisonburg and Staunton. During an aerial survey in June, DOF Forest Health staff observed damage to more than 60,000 acres. While spongy moth caterpillar feeding can remove all leaves from a tree, recovery is possible. Most trees typically survive one or two years of defoliation. Unfortunately, if a tree is weak or damaged to begin with, spongy moth feeding will lead to tree decline.
In early May 2024, federal and state agencies treated select public areas with aerial biopesticide applications to suppress spongy moth populations. DOF surveys have recently observed a decline in spongy moth populations following the biocontrol measures, a hopeful sign for our forests. Spongy moth caterpillars are also often susceptible to both an Entomophaga fungus and nucleopolyhedrosis virus, which can cause mass population crashes.
“While spongy moth infestation is severe this year, it’s encouraging to see biocontrols killing caterpillars in impacted areas,” Forest Health Program Manager Lori Chamberlin said. “These countermeasures can greatly reduce populations, resulting in less damage to our forests next year.”
Landowners looking for control methods for spongy moth can find information on DOF’s website.
For communities seeking additional spongy moth control measures, VDACS administers a Cooperative Spongy Moth Suppression Program in collaboration with local governments and the U.S. Department of Agriculture Forest Service. Applications for this program must be submitted by county governments. Spongy moth suppression program guideline details are available on the VDACS website.
“Limiting populations of spongy moth will never eradicate the pest from Virginia, but the suppression program is designed to provide relief and control in areas suffering from significant damage,” said VDACS Office of Plant Industry Services Program Manager David Gianino. “Interested localities can conduct spongy moth egg mass surveys between July and November and submit a treatment proposal for participation before November 15, 2024, for the 2025 treatment season. Localities are encouraged to review the guidelines and determine if they want to perform the required work to qualify for the program.”
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Rebecca Barnabi
