2006 Gypsy Moth Spray Blocks - County Map

The Macomb County Gypsy Moth Suppression Program is a cost-sharing program offered to Macomb County property owners, recreational areas, and special use areas.

The Macomb County Gypsy Moth Suppression Program is a voluntary program available to eligible residential, recreational, and special use property owners. The program is a cooperative effort between the USDA-Forest Service, Michigan Department of Agriculture (MDA), Macomb County and local municipalities.  Macomb County Michigan State University (MSU) Extension administers the program.

Why a Gypsy Moth Suppression Program?

The Gypsy Moth is a foreign pest with few native predators to keep populations in check.  Caterpillars feed on tree leaves, preferring those of oak, htmen, poplar, and birch.  When those are not available, other tree species and evergreens are also at risk.  Large populations can defoliate entire wooded areas.  Caterpillars in large numbers and their waste (frass) are a nuisance on residential property.  Gypsy Moths can not be eradicated, but they can be suppressed to tolerable levels.

What are the goals of this program?

• Reduce high caterpillar populations to tolerable levels.
• Reduce tree loss by preserving at least 60% tree foliage to prevent refoliation.
• Prevent indiscriminate use of chemical controls.
• Provide educational information.

How are Gypsy Moth Populations Suppressed?

The aerial application of Btk (Bacillus thuringiensis variety kurstaki) is used to reduce high populations of gypsy moth caterpillars at sites that meet MDA requirements for spraying.  Bt is a naturally occurring bacterium found in the soil and is not harmful to pets, birds, fish, wildlife, plants, beneficial insects, and humans.  Bt is applied when the caterpillars are young (usually in May) to insure the greatest impact in reducing numbers.  Alternative mechanical techniques, such as tree banding and egg mass scraping, also reduce caterpillar numbers.  The Suppression Program recommends the use of a combination of methods.

What is the Gypsy Moth Life Cycle? The gypsy moth life cycle has four main stages, and takes one year to complete: egg, caterpillar, pupae,  and moth.

Egg stage In mid-August, after mating with the male moths the females lay their eggs in “masses”.  Egg masses are generally firm, oval shaped, about the size of a quarter, and buff or tan colored.  Egg masses are laid on any surface, such as rocks, woodpiles, decks, buildings, outdoor equipment and of course, tree bark.  (It is helpful to keep yards clean and free of debris where adult moths could lay their eggs.)  Since gypsy moths complete only one life cycle per year, eggs layed in mid-August do not hatch until spring.

Caterpillar The eggs hatch into caterpillars late April or early May.  Hatch date is directly affected by weather.  The colder the spring, the later the eggs hatch.  A healthy egg mass can hold up to 1000 eggs, although the average is probably between 300 and 500.  Once the eggs hatch, the caterpillars will sit on the egg mass for a few days before they leave to  feed.  In its short lifetime, a caterpillar can eat one square meter of leaves.  The warmer the temperature, the more the caterpillars feed and develop.  Mature caterpillars are about 2” in length with long hairs grouped in bundles.  They have 5 pairs of blue dots and 6 pairs of red dots running down their backs.  Their heads are black with yellow markings.

Moths Moths, the adult stage of the life cycle, emerge from the pupal cases in mid-August.  The moths do not eat, and they live about a week.  Female moths have white wings with brown chevron or “V-shaped” markings and do not fly.  Male moths have smaller brown wings and are able to fly.  Attracted to a pheromone emitted by the female, the males can fertilize several females before dying.  The egg masses are dormant until spring (late April or early May) and the cycle begins again.

How do Gypsy Moths travel?

Caterpillars hang in trees on a silk strand and can be carried a great distance by the wind.  Humans also move egg masses or pupal cases on travel trailers, firewood, cars, etc.  Vehicular travel is how they came to Macomb County!  Make sure you do not give the Gypsy Moth a ride!

How do I know if I have the Gypsy Moth?

A number of MSU Extension bulletins can help you identify the Gypsy Moth and caterpillar.  You can also use the Macomb County MSU Extension diagnostic facility.  There is a small fee for some services.

For insect identification:

Call Macomb MSU Extension Gardening Hotline:(586) 469-5063, Monday, Wednesday, Friday, from 9 a.m. to 4 p.m.

What does gypsy moth damage look like?

Gypsy moth caterpillars feed on tree leaves creating “Swiss Cheese” type holes. They do not cause pre-mature leaf drop, browning, or curling of leaves.  They do not make a web or tent in trees.

What happens when trees are defoliated?

Trees defoliated more than 40% become stressed by using next year’s energy reserves to grow new leaves during the same season.  Healthy trees may withstand several years of defoliation.  Trees with other stress factors such as drought, could die sooner.  Evergreens are unable to replace their needles and may die when defoliated.  Keep trees watered and fertilized to lessen any damage.

Should I report a Gypsy Moth Infestation?

YES.  To determine if your property is eligible for the Gypsy Moth Suppression Program, report all infestations to the program educator at the Macomb County MSU Extension office.  An egg mass survey can be done to assess the level of infestation and determine if an area qualifies for the program.  For more information, please call: Macomb MSU Extension Gypsy Moth Suppression Program (586) 469-6430.

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