Report Gypsy Moth Caterpillars in St. Clair County

The gypsy moth is an invasive species that was first introduced to the United States in 1869. Gypsy moth has slowly spread across the United States and the first outbreak in Michigan was in the mid-1980's in central lower Michigan. At this time, gypsy moth has become established in all Michigan counties.

Gypsy moth caterpillars, the immature "larval" stage, feed on leaves of more than 300 species of trees, but they especially like oak. Their population can be controlled by natural means, such as predatory insects and fungal disease. However, when natural methods cannot keep pace with the population growth an outbreak occurs. During outbreaks, the gypsy moth population can grow in size, which can lead to defoliation of mature trees.

You are the first line of defense for protecting your property from damage by gypsy moth. Take time to inspect your trees, shrubs, structures, lawn objects, and recreational vehicles periodically for the various life stages of gypsy moth. A gypsy moth caterpillar can easily be identified by the 5 pairs of blue dots on their back followed by 6 pairs of red dots (see image below). The caterpillars pupate in summer, emerge as adult moths, mate, lay eggs and then die. Egg masses, which are laid in summer on outdoor objects and tree trunks, persist for approximately nine months until the following spring. Egg masses are about an inch wide and up to two inches long, are buff or tan in color, and appear slightly fuzzy.

Gypsy Moth Caterpillar
Caterpillar, "larval stage" - Photo Credit: Karla Salp, Washington State Department of Agriculture,
Gypsy Moth Caterpillar
Egg Mass - Photo credit: Milan Zubrik, Forest Research Institute-Slovakia,

The County of St. Clair, Michigan is collecting data to identify areas of concern for 2021 and 2022. If you have experienced an outbreak of gypsy moth caterpillars at your property, your trees have been defoliated by them, or you have seen large numbers of any other life stage, please complete the form below to assist us in tracking and managing this invasive species. A representative may contact you to obtain additional information about your gypsy moth outbreak and/or may perform a site visit, if authorized. If you have additional questions on this study/process, please contact a representative at or via phone at (810) 294-4965. For general information on the gypsy moth and how to deal with them around your home, please visit the MSUE website (here).

Your Name*
Phone Number*
Email Address*
Address where gypsy moth caterpillars were seen*
Estimation of the number of caterpillars seen in the area*

Brief description of where caterpillars were seen (Tree in backyard, side of house, all over property, etc)*
Were caterpillars seen in the same area last year?

Does the foliage of nearby trees appear to be damaged by the caterpillars?

Was the foliage of nearby trees damaged by the caterpillars last year?

Have you noticed egg masses on your property?

If you noticed egg masses on your property, how many?

Would you like to be contacted about the gypsy moth caterpillars?*

Do you give St. Clair County permission to visit your property for the purpose of inspecting for gypsy moths?*

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