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

Fall Gypsy Moth Monitoring Begins October 1, 2019 in Bay County

The Gypsy Moth Suppression Program works to protect trees in Bay County from defoliation and damage from Gypsy Moth Caterpillars to help maintain forest and tree health throughout Bay County. Wooded areas of Bay County are monitored each year to determine when and where Gypsy Moth populations are at significant outbreak levels to determine if treatment is needed to protect your trees.  All wooded areas of Bay County are susceptible to Gypsy Moth.  However, only a sampling of properties and woodlots are monitored each year to evaluate the Gypsy Moth population.  Monitoring for Gypsy Moth populations occurs throughout the year.  In the fall, Bay County Gypsy Moth Program staff visit every inhabited or recreational wooded areas in Bay County to determine if Gypsy Moth egg passes are present.  If enough egg masses are found, the wooded area is monitored again to establish the size and extent of the Gypsy Moth infestation.  When the number of egg masses passes the threshold of 300 egg masses per acre, treatment may be scheduled.  Please do not remove Gypsy Moth egg masses.  Staff will begin conducting Gypsy Moth site monitoring October 1, 2019

Letters and Landowner Authorization to Access Property for Gypsy Moth Monitoring Being Sent Out 

The Gypsy Moth Suppression Program staff are sending out letters to landowners that have woodlots and wooded areas with the best sites to successfully monitor the Gypsy Moth Populations in Bay County.  To conduct this monitoring, staff need the cooperation of landowners like you.  Letters are being sent out to landowners with a description of 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 by the end of September.  The Landowner Authorization for Gypsy Moth Monitoring Form will allow our staff to conduct monitoring on your property.  When we get your form with contact information, we will provide you with field report updates on what we have found in your area. By providing your e-mail address we can provide you with the field report updates electronically instead of by mail to help keep program costs down.  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

Gypsy Moth Update - June 21, 2019

 Figure 1 above shows second and third
instar Gypsy Moth caterpillars feeding
on oak leaves. [Alicia Wallace, June 2019]



Gypsy Moth caterpillar numbers are up in many
parts of Michigan this summer. Our cold spring
delayed their hatching but they are already
causing defoliation and tree damage in parts
of Barry, Clare, Gladwin, Ionia, Roscommon
and Washtenaw counties. This outbreak
started in 2018 when many of the same areas
of the state had significant leaf lose last
summer due to the feeding gypsy moth
caterpillars. Aspen and oak top the list of
over 500 preferred host species on which
gypsy moth caterpillars will feed on into

Mature trees can usually withstand
gypsy moth defoliation and simply grow
more leaves; however, multiple years of
defoliation can weaken and even kill trees.

Many folks confuse the gypsy moth with a
few of our native species of hairy caterpillars
like the Eastern Tent Caterpillar and Forest
Tent Caterpillar. The Eastern Tent caterpillars
are the ones who make the nest or webs in
small under story trees like crab apple and
plum.  All three species of caterpillar feed
on a wide variety of trees in spring each year.
Unfortunately all can be present in the same
woodlot adding more stress to our trees.

2019 Emerald Ash Borer (EAB) Spring Treatment Has Been Completed

Treatment to protect ash trees from Emerald Ash Borer (EAB) was completed the week of June 10, 2019. The application firm had two crews that worked long hours to complete the ash tree injections. Ash trees will be monitored throughout the summer to evaluate their continued health.

Treatment Information: 

  • Injectable Insecticide Common Name: Tree-age
  • Active Ingredient: Emamectin Benzoate
  • Method of Application: Direct tree injection through one way ports that do not allow the insecticide to leak out of the tree.
  • Application Firm: Injection treatments will be done by Kinnucan Tree Experts &Landscape Company.
  • Affected Trees: Specific areas included in the 2019 EAB Spring Treatment project are located in the south-east quarter of Bay City (east of the Saginaw River, south of Columbus Avenue), Portsmouth and Merritt Township parks, and the Bay County Golf Course.  Other geographic areas will be done in future years.
  • To see a map of the 2019 treatment area, please click on the following link:  2019 EAB TREATMENT MAP 

If your have any questions or for further information, please contact Alicia Wallace, Bay County Gypsy Moth Suppression Program,515 Center Ave. Suite 503, Bay City, Michigan 48708 at 989-895-4195 or via email at


2019 Gypsy Moth Spring Treatment Has Been Completed

On May 24, 2019 treatment was completed to control outbreak level populations of Gypsy Moth Caterpillars in Bay County. The weather was perfect and spray operations went smoothly. A preliminary survey of the treated sites indicates that the treatment was effective and will successfully protect the trees.

The areas that were treated are shown on the map below:



To view maps of each of the specific 2019 treatment area, please  click the links below:

· 2019 Treatment Map - Gibson Township Section 18 - 267 acres along Flajole Road
· 2019 Data Sheet - Gibson Township Section 18 - 267 acres along Flajole Road
· 2019 Treatment Map - Gibson Township Sections 35 & 36, and Mount Forest Township, Sections 1 & 2 - 107 acres at the south end of Nine Mile Road
· 2019 Data Sheet - Gibson Township Sections 35 & 36, and Mount Forest Township Sections 1 & 2 - 107 acres at the south end of Nine Mile Road
· 2019 Treatment Map - Kawkawlin Township Sections 13 & 24 - 32 acres at the east end of River Road 
· 2019 Data Sheet - Kawkawlin Township Sections 13 & 24  - 32 acres at the east end of River Road

The biological insecticide Foray 48B will be used for this treatment. Foray, a water-based insecticide formulation, is OMRI certified organic so it can be used on organic foods. The active ingredient is Bacillus thuringiensis variety Kurstaki (Btk). Research has shown that Btk will only kill the caterpillars of moths and butterflies that are feeding at the time of application. It is not known to affect humans, pets, birds, fish or other insects.

· Foray48B Pesticide Label
· Product Safety Data Sheet


The Al’s Aerial Spraying,LLC of Ovid Michigan will treat using a bright yellow airplane that will fly low over the tops of the trees. 

Emerald Ash Borer (EAB) Spring Treatment

Treatment to protect ash trees from the invasive Emerald Ash Borer (EAB) will be done in Spring 2019.

Pruning Oak Trees:

Oaks trees are some of our favorite trees and are also favorites of gypsy moths. Gypsy moth populations across Bay County remain low so they should not cause problems for the oak trees this summer. Unfortunately a deadly fungus disease called oak wilt is now becoming active along with the tiny picnic beetles that carry the disease from one tree to another. They are attracted to wounds on trees so stop pruning your oak tree now until next fall. For more information on oak wilt click HERE

National Invasive Species Awareness Week:  Flowering Rush

The beautiful flower of flowering rush (Butomus umbellatus) may look lovely, but is invasive in Michigan. Flowering rush is an aquatic invasive plant that lives along the edges of lakes, streams and wetlands. It is a perennial plant that grows to a height of 3-5 feet. The pink flower that blooms in June makes it easy to identify at that time. This plant is spreading throughout the Saginaw Bay watershed with the majority of sightings along the Shiawassee and Saginaw Rivers. It is important for invasive species managers and the public to help map the extent of flowering rush through MISIN. Knowing the extent of flowering rush will allow managers and organizations to prepare efficient management plans. For more information please click HERE.

Emerald Ash Borer (EAB) Treatment Program 

As you're enjoying the summer trees in full bloom around Bay County know that the staff of the Gypsy Moth Suppression Program have been working hard to save the public trees throughout our community. To protect our trees and horticulture form non-native invasive species that threaten to upset the natural balance in our area. One such non-native invasive species is the Emerald Ash Borer (EAB) which arrived in Bay County around 2007.

Since the EAB treatment program began five years ago, staff has been able to save and maintain over 3,400 ash trees on public lands. These trees provide not only shade to the areas where they stand but many ecological and economic benefits. They reduce heat in the city saving on summer air conditioning costs; reduce winds in the winter saving on heating costs; produce oxygen, remove carbon dioxide and other pollutants from the air improving our air quality and reduce storm water run-off. 

The Gypsy Moth Suppression Program staff have begun measuring and evaluation ash trees in Bay County to determine which trees are likely to survive an EAB attack in order to determine which trees have the best success rate for treatment.

Look for these signs and symptoms on your ash trees as they may be signs of an EAB Infestation: Thinning of upper canopy of the tree; Water Sprouts on trunk and Branches; Cracks in the bark; S-shaped tunnels under the cracks; Wood pecker damage; D-Shaped holes in the Bark. If you suspect that you have Emerald Ash Borer (EAB) infesting your ash trees, please contact Alicia Wallace, Program Coordination of the Bay County Gypsy Moth Suppression Program at 989-895-4195 or for more information about what you can do. 


 Websites of Interest

  • Check out the United States Department of Agriculture (USDA) Animal and Plan Health Inspection Service website Hungry Pests for more information on various invasive pests and what you can do to prevent their infestation. 

Articles of Interest

Gypsy Moth Suppression Program


The Bay County Gypsy Moth Suppression Program was established in 1989 to control outbreak levels of the invasive species Gypsy Moth (Lymantria dispar) occurring in Bay County. Heavy infestations of the Gypsy Moth can cause area wide damage to trees, woodlots and adjacent property when the feeding caterpillar life stage eats the leaves off of area trees (defoliation). The favored tree types targeted by Gypsy Moths are oak, polar, 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 educating the public on prevention and control methods, and conducting surveillance monitoring in wooded areas to evaluate the prevalence and density of Gypsy Moth at its various life stages. When monitoring shows populations are at significant outbreak levels, treatment is provided to reduce the population and control the infestation.


Services offered by the Gypsy Moth Suppression Program include:

  • Monitoring all wooded and residential areas of Bay County for the presence of Gypsy Moth life stages.

  • Conduct suppression/control activities in heavily infested areas of the county. This includes determining where out-break level populations occur, contracting with an aerial applicator and conducting treatment projects in highly infested areas, and evaluation of treatment results.

  • Cooperate with the Michigan Department of Agriculture's (MDA) grant program for Gypsy Moth suppression to ensure maximum reimbursement on treatment and administrative costs. By following MDA guidelines and participating in the grant program, Bay County is able to reduce the cost of the program for Bay County taxpayers.

  • Conduct educational programs for schools, property owners, and local civic groups. The program utilizes Bay County Pinconning Park as a staging area for many of these presentations, which include information on the life cycle of the gypsy moth, how it fits into our local ecology, and methods for controlling the gypsy moth.

Gypsy Moth Suppression Program Links of Interest

Emerald Ash Borer

The Emerald Ash Borer (EAB) is an Asian beetle that moved into the south-east corner of Michigan some time in the early 1990's. It's larvae feed on the cambium or conductive tissue just under the bark of ash trees.

The emerald ash borer(EAB) is a very destructive insect that kill all species of North American ash trees. It is responsible for the death of millions of trees throughout Michigan and it has spread to 13 additional states and 2 Canadian Provinces. First found in the Detroit area of south eastern Michigan in 2002, the EAB were most likely introduced into the USA in wood packing material during the early 1990's. The Bay County Gypsy Moth Suppression Program responded to threat to our local forests by adding the EAB education and monitoring to Gypsy Moth Program Activities.

Beneficial Insects

Many insects and related arthropods perform functions that are directly or indirectly beneficial to humans. They pollinate plants, contribute to the decay of organic matter and the cycling of soil nutrients, and attack other insects and mites that are considered to be pests.

Asian Lady Beetle vs Ladybug
There is no difference. Both are lady bugs but the Asian variety has the habit of moving indoors for the winter in large numbers. This is to make finding a mate easier in the spring.

Lady Bug Larvae Resemble Tiny Alligators

Other Invasive Pests & Plants

Besides the Gypsy Moth and the Emerald Ash Borer (EAB), there are many insects and plants that can invade our yards and woodlands. Please check out our information regarding Other Invasive Pests & Plants.

Tree and Garden Articles/Information

Red Squirrel Injury to Spruce Trees in Winter (MSU Extension 01/21/2013)
Pesky red squirrels will feed on spruce buds when other foods become scarce in the winter.

Common Susprects Involved in Winter Landscape Damage
(MSU Extenstion 01/04/2013)
Identifying these pesky, winter, landscape pests by the location of the damage they cause.

Season Ending Tasks in the Garden
(MSU-Extension 12/07/2012)
Even though the weather is getting colder, there are still many tasks to do in your garden before winter settles into the area. This article can explain what you should be doing now to ensure you have a healthy garden next spring.

Additional Information & Assistance

Bay County Gypsy Moth Suppression Program staff members are available to visit your home or site to check for invasive pests such as gypsy moths, emerald ash borers and other native or non-native invasive pests that may be affecting the health of your trees and shrubs. Please call 989-895-4195 if you have any questions.


For more information about invasive pests, check out our
"Other Invasive Pest" Webpage