Gyspy Moths

Asked July 10, 2020, 3:19 PM EDT

I live in White Birch Lakes in Farwell, MI We are being taken over by Gyspy Moths. Our Hardwood (Oak Trees) are almost bare from the leaves being eaten. Do you have any suggestions.

Thank you
Kathy Morrison

Clare County Michigan

1 Response

Gypsy moths are defoliated trees across much of Michigan in the 90's, and they definitely are making a comeback. Gypsy moth populations typically remain high for two to three years then collapse and return to low levels. This population collapse usually is the result of a virus disease called NPV that affects gypsy moth caterpillars. When populations are high, the caterpillars compete with one another for food and resting spots. Stressed caterpillars become more susceptible to the NPV disease. After a year or two of heavy defoliation, the NPV disease, in combination with a fungal disease and other natural enemies, will generally control the outbreak. Gypsy moth populations usually remain at low levels for five to 10 years and sometimes longer. Eventually, some factor triggers another outbreak and a new cycle begins. The information in the links below will give you information on this pest and how to deal with it.

Because oak trees are so tall, the main defense is an aerial application of Bacillus thuringiensis var. kurstaki (Btk), used to reduce high populations of gypsy moth caterpillars at sites that meet certain guidelines for treatment. You may wish to contact your DNR in Clare County to see if any spray programs are being planned.