Gypsy Moth Suppression Program

Alicia Wallace - Program Coordinator
Jeremy Lowell - Assistant Program Coordinator

Bay County Building
515 Center Avenue, Suite 503
Bay City, Michigan 48708-5941
Voice: (989) 895-4195

Gypsy Moth - Information about this Non-Native Invasive Insect

Overview of the Gypsy Moth Suppression Program 

 The Bay County Gypsy Moth Suppression Program was established in 1989 to control outbreak levels of the invasive species Lymantria dispar (Gypsy Moth) that were beginning to cause damage to area trees. Heavy infestations of the Gypsy Moth cause area wide damage to trees, woodlots and adjacent property when the caterpillar life stage eats the leaves off of area trees (defoliation). Gypsy Moths prefer to feed on oak, poplar, birch, willow, apple, and even spruce and pine. These are the dominant trees types in our landscape and woodlots. Defoliation makes the trees susceptible to disease and even death. The Gypsy Moth program serves to protect trees in Bay County from defoliation and damage from Gypsy Moth caterpillars by controlling Gypsy Moth Populations before they reach outbreak levels. 

The 2020 Gypsy Moth Egg Mass Monitoring is Underway! 

The Gypsy Moth Suppression Program is gearing up to conduct their fall and winter Gypsy Moth egg mass monitoring starting in October 2020and continuing through January2021. This monitoring will help determine the areas that will require spring treatment in 2021. Gypsy Moth monitoring done throughout this past spring and summer have shown that there are a few areas in Bay County where gypsy moth populations are still on the rise. Check out our detailed Heat Map which shows areas where higher numbers of gypsy moth egg masses were found during the last fall monitoring.  Areas with more than 300 egg masses per acre we rescheduled for treatment in spring of 2020 where allowed.

Services Offered by the Gypsy Moth Suppression Program

To help protect the health of trees in Bay County, the Gypsy Moth Suppression Program provides the following services: 

  • Surveillance Monitoring:  Conduct surveillance monitoring in wooded areas to evaluate the prevalence and density of Gypsy Moth at its various life stages to determine if they are reaching outbreak level that can damage area trees. All wooded and residential areas of Bay County are monitored. When monitoring shows populations are at significant outbreak levels, treatment is provided to reduce the population and control the infestation. This includes determining where out-break level populations occur, contracting with an aerial applicator, and evaluation of treatment results.
  • Public Education:  Staff also provides education to the public on what to look for and best tree care practices to maintain healthy trees that can withstand attach by Gypsy Moths and other invasive species that could damage our trees. Staff presents educational programs for schools, property owners, and local civic groups, which include information on the life cycle of the Gypsy Moth, how it fits into our local ecology, and best management practices to control Gypsy Moths.
  • Treatment to Suppress Gypsy Moth:  Staff conduct treatment to help with the suppression of Gypsy Moth.  All treatments are compliant with National Pollution Discharge Elimination System (NPDES) permit requirements and Michigan Department of Agriculture and Rural Development’s (MDARD) Regulations 636 and 637 for the use of pesticides. Continue to follow guidelines and management practices outlined by USDA Forest Service and MDARD.

Click on the link above for answers to some of the Frequently Asked Questions about Gypsy Moth

Landowner Authorization Forms

The Gypsy Moth Suppression Program staff sent out letters to landowners that have wood lots and wooded areas with the best sites to successfully monitor the Gypsy Moth Populations in Bay County. To conduct routine yearly monitoring, staff needs the cooperation of landowners like you. Letters were sent out to landowners describing how and when Gypsy Moth monitoring is conducted, along with a Landowner Authorization for Gypsy Moth Monitoring Form to fill out and send back to our department. The Landowner Authorization for Gypsy Moth Monitoring Form allows staff to conduct monitoring on your property in order to monitor and treat the invasive non-native Gypsy Moth. Staff will provide homeowners with field report updates on what they find in your area. By providing your e-mail address staff can provide you with the field report updates electronically. If you have any questions regarding this program, other invasive species, or any tree health concerns please contact the Gypsy Moth Program at 989-895-4195 or at None of your contact information will be shared outside of our office.

2020 Bay County Spring Aerial Treatment to Control Gypsy Moth Completed

Aerial treatment to control out-break level Gypsy Moth infestations were done on the morning of Wednesday, May 27, 2020 between the hours of 6:30 a.m. and 8:00 a.m. The weather conditions, Gypsy Moth caterpillar development, and the tree leaves were conducive to successful aerial treatment application.

  • Biological Insecticide Common Name: Foray 48B, this product is OMRI certified organic so it can be used on organic foods. Active Ingredient in the insecticide: Bacillus thuringiensis kurstaki (Btk)
  • Method of Application: Aerial application by a yellow fixed-wing airplane flying low over forested areas.
Areas to be treated: One wooded area in Gibson Township where the gypsy moth caterpillars will damage and defoliate local trees. Property owners in treatment areas have been notified by direct mail of the intent to treat the trees on their property.


Maps for the2020Treatment Area:

Pesticide Label and Information for Foray 48B:

For further information or if you have questions, please contact Alicia Wallace, Bay County Gypsy Moth Suppression Program Coordinator, at 989-895-4195 or

Press Release for 2020Bay County Gypsy Moth Aerial Treatment( 05/14/20)
Aerial Treatment for the suppression of Gypsy Moth in Bay County will be done between May 24 –June 5, 2020. The Bay County Gypsy Moth Suppression Program will conduct Aerial Gypsy Moth Treatment in the next few weeks at a heavily infested 381 acre woodlot in Gibson Township in northern Bay County. Monitoring surveys show that the Gypsy Moth population in that area has reached outbreak levels, and is likely to damage the trees in the area. This population may also spread to other areas of the county if not treated.


Gypsy Moth Caterpillar Hatch Video

Baby Gypsy Moth Caterpillars are freshly hatched and ready to start eating the leaves off local trees.