Although later than originally anticipated, areas of Clinton Township will be sprayed for Gypsy Moth control. Two planes are to be used to spray all the designated areas. Properties affected received notices by mail in April.
Macomb County MSU Extension Gypsy Moth Suppression Program
The Macomb County Gypsy Moth Suppression program is a joint effort between the county and impacted communities, recreation areas and special use areas. The program is administered by the Macomb County MSU Extension.
The suppression program’s ultimate purpose is to assist with the aerial application of Bt (Bacillus thuringiensis) to qualifying areas in an effort to reduce intolerably high populations of gypsy moth caterpillars. The program also provides information about additional techniques to help reduce caterpillar numbers when levels are not high enough to qualify for aerial treatment. Prospective treatment sites are determined using MDARD guidelines. Regardless of whether an area qualifies for aerial spray, a combination of methods can and should be employed to combat the increase and spread of infestation.
The goals of this program are to:
Gypsy Moth Background
The gypsy moth (Lymantria dispar) is a foreign pest with few native predators to keep populations in check here in the United States. First introduced in Massachusetts in 1869, it has spread across the much of the northeast. Gypsy moth outbreaks began to occur in the lower peninsula of Michigan in the mid-1980’s. Caterpillars feed on tree leaves, preferring those of oak, aspen, poplar, and birch but will feed on over 500 types plants throughout the summer. Large populations can defoliate entire wooded areas. Caterpillars in large numbers (and their waste, frass) are a nuisance in residential areas. Gypsy moths cannot be eradicated, but they can be suppressed to tolerable levels.
Bt Information and Usage
The main defense is an aerial application of Bacillus thuringiensis var. kurstaki (Btk), used to reduce high populations of gypsy moth caterpillars at sites that meet specific guidelines for treatment. Btk is a naturally occurring bacterium found in the soil and on plants and is not harmful to pets, birds, fish, plants, beneficial insects, or humans.
Thousands of Bt varieties exist in nature, each with its own unique characteristics. Most Bt varieties are insect pathogens that cause disease in specific groups of insects, and several are registered with the U.S. Environmental Protection Agency (EPA) as microbial insecticides. Though Bt products can be highly effective in controlling specific insects, they have little impact on other animals. Therefore, sprays made with Bt pose significantly less risk of affecting non-target organisms than conventional chemical insecticide sprays. Btk is commonly used by organic gardeners and farmers, as well as some conventional farmers, to control caterpillar pests of fruits and vegetables.
The Bt products used to control gypsy moth during outbreaks are made from a strain known as Bacillus thuringiensis var. kurstaki HD-1, or more simply, as Btk. Btk has been used for gypsy moth control in the northeastern U.S. since 1961 and in Michigan since 1985.
Btk specifically targets only caterpillars of a certain age. It 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, egg mass scraping, and hormone traps to help reduce populations. The Suppression Program recommends the use of a combination of methods.
Caterpillar Defoliation Activity
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. In addition to damage to the trees, gypsy moth caterpillars can be a nuisance if populations are high enough. Caterpillars and their frass (feces) can drop down from trees on to sidewalks, driveways, yards, porches, and vehicles. The hairs on the caterpillars can cause irritation or an allergic reaction to bare skin. Frass can stain surfaces, especially if it is rained on or becomes wet.
Tree defoliation by the caterpillars can have a significant negative impact on tree health. 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. Evergreens are unable to replace their needles and may die when defoliated. Keep trees watered and fertilized to reduce any stress.
When Btk grows, it produces spores and non-living protein crystals. When gypsy moth caterpillars eat leaves that have been sprayed with Btk, the protein crystals dissolve in their digestive system and become toxic. This can occur only in caterpillars because of the many unique conditions present in their digestive system. For example, caterpillars have an alkaline digestive system, while humans and many other animals have acidic digestive systems.
Soon after caterpillars feed on leaves sprayed with Btk, they stop feeding. If the caterpillars consume enough Btk, they die after a few days from a combination of starvation, damage to their digestive system and bacterial growth within their bodies.
Community Follow Up
It is important to communicate all gypsy moth infestations to the MSU Extension Gypsy Moth program staff. Egg mass surveys are done in late fall to determine the level of infestation and whether an area qualifies for the program.
Contact the MSUE Gypsy Moth program by calling 586-469-6432 or emailing Katherine.firstname.lastname@example.org
More information about Gypsy Moth life cycle, Bt and other suppression activities by visiting:
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April 23, 2020
NOTICE OF AERIAL SPRAY FOR GYPSY MOTH SUPPRESSION
Dear Property Owner,
Your property is located in a treatment area (spray block) for the Gypsy Moth Suppression Program. Gypsy Moth egg mass surveys have determined that infestation levels qualify your area for this program. Aerial spraying will occur in mid to late May 2020. Weather conditions and caterpillar development will determine the exact spray date.
The Gypsy Moth Suppression Program reduces nuisance caterpillar populations to tolerable levels and preserves tree foliage to prevent tree loss. Program costs are shared by Macomb County and your local municipality. There is no additional cost to you as a property owner.
All or a portion of your property is to be sprayed with a biological insecticide called Bacillus thuringiensis, commonly known as Bt. Bt is a naturally occurring bacteria found in soil, and it only affects caterpillars actively feeding on treated leaves. This insecticide option has been used in Michigan since 1985 and in Macomb County since 1993 when the Gypsy Moth Suppression Program started in Macomb County.
Once sprayed, the area may be entered immediately and there is no restriction on property use. The Bt material will be applied by airplane in a very fine mist that is not always observable from the ground. After 4 to 6 hours, the material will be dried on the leaves and rain should not be a concern.
Spray block maps are available at our office, or your local municipality offices. If you have any questions, please call 586-469-6432. While our office is currently closed, this number is being monitored.
For more information on the gypsy moth or Bt, visit this website:
Terry Gibb, Senior Extension Educator
Natural Resources & Government/Community Vitality