CADILLAC — Gypsy moth caterpillars were plentiful this spring and the Michigan State University Extension is getting lots of calls about the pests.

Wexford County MSUE Integrated Pest Management educator Erin Lizotte said gypsy moth caterpillar populations are extremely high throughout the oak forests in northern Michigan. The presence of caterpillars has been a nuisance, and many oak trees have been severely defoliated as the caterpillars continue to eat the leaves.

Fellow MSUE Natural Resources educator Julie Crick said the caterpillar numbers have reached their peak. She also said in talking with the Department of Natural Resources Forest Health Technician Scott Lint that populations haven't been this high since the 1990s. She also said the severity is different depending on the area of northern Michigan. But what isn't up for debate is that if a section of forest has oak trees the caterpillars are there.

She said the areas where the forest is comprised of mostly oak trees include parts of Crawford, Montmorency and Kalkaska Counties, and the western portion of Wexford County.

The best thing a person can do is from November to May seek out gypsy moth egg masses and scrape them off into soapy water, according to Crick. Each mass can contain up to 1,000 eggs, which means 1,000 caterpillars hatching the following spring. Egg masses can be found on homes, outdoor furniture, among other places.

When scraping egg masses, the MSUE suggests taking care not to shatter the crumbly egg mass, as the tiny eggs will just float to the ground, not allowing them to be killed. A flat index card or plastic container can be used to funnel the cluster as it drops away from its point of attachment. If you wait until spring, watch the egg masses until hatchlings cluster on the old egg mass while their bodies acclimate to their new surroundings. Using a spray bottle with soapy water, soak them before they have a chance to disperse into the tree canopy, according to the MSUE.

Crick also said the eggs will be laid by the end of August, but it is best to wait until later in the year to get rid of them. This allows natural predators, like a parasitic wasp, to keep the moths in check. There also is a virus and a fungus that also help to control the populations, according to Crick.

The MSUE also suggests installing sticky bands on trees to help keep the gypsy moth caterpillars from climbing back up the trunk of the tree. During the hottest parts of the day, the gypsy moth caterpillars spin a web to the ground to escape the heat and then attempt to climb back up the trunk once it cools.

Sticky bands prevent the caterpillar’s ascent and dozens, if not hundreds, of caterpillars, will congregate below the sticky tape where they can easily be targeted with a soap and water spray or plucked off and collected in a bucket of soap and water.

Sticky bands can be constructed using duct tape and petroleum jelly. Simply wrap three overlapping bands of duct tape, sticky side down on the bark, around the tree. Then, take a small amount of petroleum jelly on your finger and run it across the middle band. Applying petroleum jelly directly to the bark is not recommended and could injure the tree.

As for trying to help a tree that has been attacked by the gypsy moth caterpillar, MSUE suggests watering a severely defoliated tree if it has been five or more days without rain. Watering will relieve some of the stress on the trees as they work to grow leaves to replace what the gypsy moth caterpillars consumed. 

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