by Kate Evans
The telltale signs of spongy moth damage is visible now in multiple forest locations in Morgan County.
State agriculture officials warned of tree trouble coming as they predicted larger numbers of the moths, formerly known as gypsy moths, would be hatching this summer. A cooperative spraying program has already dropped spray on more than 2,000 acres in the county to interrupt the life cycle of the spongy moth.
Forested areas are still showing impacts from the moth, which eats the spring leaves off mature trees.
County landowners have been noting increased numbers of spongy moth (Lymantria dispar) caterpillars this year with pupae and adult moths now appearing.
West Virginia officials are concerned about possible tree mortality, disease from tree stress, deforestation and defoliation that could occur from the spread of the spongy moth without treatment to infested properties.
State officials say the damage will likely be much worse next year.
Scott Hoffman, West Virginia Department of Agriculture Gypsy Moth Cooperative Suppression Coordinator, said in a phone interview that they are seeing a lot of defoliation in Morgan County from the spongy moths. Most of the damage is on Cacapon Mountain and in Great Cacapon, he said. In some areas, the defoliation is heavy while other areas aren’t so affected.
Officials have also checked Sideling Mountain and Sleepy Creek Mountain, Hoffman said. Caterpillar infestations and tree defoliation have been seen in those areas.
Where the insects are now in their life cycle varies in location, Hoffman said.
In some areas, 50% of the spongy moth caterpillars have already gone to the pupae stage. In a few places, the moths are abundant. In other areas, the insects are still caterpillars.
State forestry officials are seeing some caterpillars that have the Nucleopolyhedrosis Virus (NPV) and the Entomophaga maimaiga fungus, but they have not seen a population collapse from either, Hoffman said.
Both the virus and the fungus are present in nature but hadn’t gotten rolling until the past week or two.
Hoffman said Morgan County hadn’t been treated for spongy moths since 2018. He said that the insect’s populations will build up and be active for a few years, then the same rise in population will happen a few counties away.
Morgan County’s spongy moth population has been low but has been building, Hoffman said. He expects next year’s population will be much higher and the damage much worse.
The spongy moth feeds on hundreds of different trees and shrubs and is causing timber loss and impacting wildlife, habitat and recreation. Their preferred tree of infestation are oaks, but they attack other hardwoods.
Repeated heavy defoliation by the insect kills trees. The mortality of hardwood trees after two successive years of defoliation can reach 80%. Trees can also be affected by other pests and diseases since they are weakened.
The young caterpillars and spongy moth egg masses are spread by wind and also unknowingly transported in firewood, trucks, campers, RVs and other vehicles.
Risks to moths
The Nucleopolyhedrosis Virus (NPV) occurs naturally in spongy moth populations and spreads through caterpillar contact during outbreaks, causing a population crash. Look for dead caterpillars hanging from tree trunks and other items in an upside-down “V” formation to indicate NPV infection.
The Entomophaga maimaiga fungus has been killing spongy moth caterpillars in northeastern states. The fungus remains in the soil and infects the caterpillars that come into contact with its spores. Moist soil helps activate the fungus. Caterpillars infected with the E. maimaiga fungus stay attached to tree trunks but hang straight down.
There are some natural predators of spongy moths, but they don’t have a lot of effect on their populations, Hoffman said. Many birds prey on the spongy moth caterpillars, adults and/or their egg masses and help decrease their populations.
Predatory birds include the black-capped chickadee, tufted titmouse, white-breasted nuthatch, starling, common grackle, Eastern bluebird, the American robin, phoebe, blue jay, downy woodpeckers, brown thrasher, Baltimore orioles, American crow, grey catbird, house wren, red-winged blackbird, Eastern towhee, chipping sparrow, indigo bunting, flicker, rose-breasted grosbeak, yellow-billed cuckoo and scarlet tanager.
Mice, shrews, chipmunks, skunks, raccoons and squirrels will also feed on spongy moth caterpillars and pupae on the ground and at the base of trees.
What people can do
Hoffman advised landowners to collect egg masses on trees they want to protect.
Hanging folded-over burlap or cloth on trees with baling twine will give the caterpillars a place to collect and turn into pupae. Female spongy moths will also lay their eggs there.
Scrape the egg masses off the tree bark and squish them, Hoffman said. If you see the larvae (caterpillars), the females are bigger. He recommended smashing them.
Each female you kill before it can lay eggs will save you a lot of trouble next year, Hoffman said. That’s 250-500 larvae that won’t be feeding on your trees the next year. People can also use a contact insecticide labeled for spongy moths.
Hoffman said that the size of the egg masses indicate the health of the spongy moth population. Egg masses the size of a dime mean that the population could be declining and isn’t very healthy. Long, large egg masses could indicate that the population is building.
Hoffman encouraged landowners to register for the Gypsy Moth Cooperative Suppression Program to help slow the spread of the insect.
Adjacent landowners can join together and combine their properties to meet the acreage requirement for aerial spraying, Hoffman said. There is a minimum requirement of 50 acres of wooded land per block.
Sign-ups are being done in July and August for spraying. A survey deposit must be submitted with the application.
Some 2,861 acres in Morgan County were sprayed in May for gypsy moth, mostly on Cacapon Mountain and in Great Cacapon, Hoffman said. The acreage sprayed included state land, private lands and developments.
Two different spraying products are used — Bacillus thuringiensis var.kurstaki (Btk) and Mimic (Tebufenozide), he said. Btk is considered safe in regards to humans and animals. Mimic has low toxicity to other insects and animals.
Once applications are received, someone from the Department of Agriculture will come out to look at your property to see if it qualifies for spraying, Hoffman said. They will conduct an egg mass survey. Areas with 500 egg masses per acre or more that are wooded residential, wooded recreational, or non-residential woodlands can be designated for possible treatment.
Hoffman said that applications are available on the WVDA website, at local West Virginia University Extension Offices and also through the WVDA Charleston and New Creek offices.
For more information, contact WVDA Assistant Director Quentin “Butch” Sayers at email@example.com or WVDA Gypsy Moth Program Coordinator G. Scott Hoffman at firstname.lastname@example.org 304-788-1066.