Spongy moths (formerly called gypsy moths) are one of the most damaging invasive pests in Michigan. Their caterpillars strip leaves from oaks, aspens, and other hardwoods, weakening and sometimes killing trees over repeated years. Clare County has active monitoring and treatment programs through the Conservation District.
How to Identify Spongy Moths
- Egg masses (fall-spring): Tan, fuzzy patches about the size of a quarter, found on tree trunks, firewood, outdoor furniture, and vehicles.
- Caterpillars (May-July): Hairy caterpillars with pairs of blue and red dots running down their backs.
- Adults (July-August): Males are brown and fly; females are white with dark markings and do not fly.
What to Do
- Check your property in late winter or early spring for egg masses. Scrape them into a bucket of soapy water to destroy them.
- Contact Toni Maize at (989) 539-6401 to report heavy infestations. The Conservation District tracks populations and coordinates treatment.
- Set traps. The District can supply or recommend pheromone traps to monitor moth activity on your property.
- Consider treatment. For significant infestations, aerial spraying with Foray 48B (a biological insecticide made from Bt bacteria) is the most common approach. It targets caterpillars and is safe for people, pets, and wildlife. The District coordinates group treatment areas to keep costs down.
- Rent tools. The Conservation District rents invasive-species management equipment at $12-25 per day — brush cutters, sprayers, and applicators.
Other Invasive Species
The Central Michigan Cooperative Invasive Species Management Area (CM-CISMA) covers Clare County and provides identification help, educational workshops, and management resources for invasives like autumn olive, phragmites, and Japanese knotweed. Contact the Conservation District to connect with CM-CISMA programs.
Common Mistakes
- Do not move firewood. Spongy moth egg masses hitchhike on firewood. Buy it where you burn it.
- Do not wait. Small populations are easier to manage. Scraping 20 egg masses now prevents thousands of caterpillars later.
- Do not use broad-spectrum insecticides. They kill beneficial insects along with the moths. Bt-based products like Foray 48B are targeted and effective.