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Gypsy Moth Suppression Program

Posted on: May 1, 2012

[ARCHIVED] Gypsy Moth Update

Spraying of 4,223 acres in Roscommon County for gypsy moths will soon be upon us, that is, if it warms up. (Acerage was treated on May 18, 2012)

This spring is very similar to the year of 2010 when the first hatching caterpillars appeared on April 14, 2010 and spraying occurred on May 21, 22,23 and 24 . In order to time the spraying project accurately the following critical factors must be taken into consideration. They are caterpillar growth, leaf development and weather.

Unlike the Eastern Tent Caterpillar, which is found in a silk tent in a branch of a wild cherry tree or shrub, the gypsy moth egg mass is tan-buff in color and intertwined in a matting of hair from the female’s body. It is water repellent and well insulated. These egg masses range in size from 1 to 3 inches long and are sometimes tear dropped in shaped and about the size of a quarter. Each egg mass can contain 50 to 1,500 eggs. Typically hatching occurs around the first week in May and coincides with the time the tree buds start to open, that is, if we can maintain temperatures at night in the upper 40’s low 50’s and days in the mid to upper 60 degree range.

Each fall landowner’s are told not to destroy the egg masses so that the collected field information can later be verified. I recommend not removing egg masses until the month of April. Scraping egg masses into a bucket of soapy water and letting them sit for a day until they are dead is a great defense procedure landowner’s can use. If you did not get a chance to remove them and they have hatched you can either spray the caterpillars with a bottle of soapy water or collect and soak them in a bucket of soapy water for a day or 2 and then dispose of them.

The timing for spraying Foray 48B; Certified for Organic Production; containing a natural soil bacteria called “Bacillus thuringiensis subspecies kurstaki (Btk)”used by Roscommon County’s Suppression Program is about 80 percent effective against all actively feeding caterpillars while they are in the first 2 growth stages of their lives (less than 1/2 inch in size). Eradication is not possible. It is then that the Btk can survive long enough in the gut of the caterpillar to secrete a protein crystal that destroys part of the digestive system. From there, the bacteria flood into the circulatory system of the caterpillar and kill it within a few days. As the caterpillars get larger, the efficiency of Btk diminishes. Btk will remain potent for about a week and is broken down by sunlight. This Bt, a natural soil bacterium, is cultured using water and nutrients such as sugars and starches, in a fermenting process similar to brewing beer. The final product, Btk, contains almost all water, leftover growth medium, carbohydrates, and inert ingredients that are approved as food additives. Foray 48B contains Btk that has been approved safe by both the OMRhode Island (Organic Materials Review Institute) and the Food and Drug Administration in Washington DC. It has been used to control caterpillar defoliation of fruits and vegetables for many years and is not harmful to water, humans, pets, birds, fish and other wildlife.

Leaf development and weather are also critical factors in determining the date of the spray. As trees begin to break bud and leaves flush, the leaf canopy closes. For the spray to work, it must land on the leaves being eaten by the caterpillars. If the canopy is underdeveloped at the time of the spray, the Foray 48B will settle uselessly to the ground. An overdeveloped canopy, however, will intercept too much of the spray and only those caterpillars feeding at the very tops of the trees will ingest enough of it to poison themselves. As for the weather, a great spray day would be 1 with cool temperatures, high humidity, less than 5 mile per hour winds, and zero precipitation. But, if the day starts out great and the weather deteriorates later, than the spraying will be suspended until the weather improves.

Al’s Aerial Spraying, LLC 3473 North Shepardsville Road, Ovid, MI 48866 (Phone: 989-934-5067) is hired to do Roscommon County’s spring spraying this year and expects the project to take 1 to 2 mornings. Spray cost is: $24.74 per acre. If you would like more information please contact the Gypsy Moth Office at:
County Building
500 Lake Street
Roscommon, MI

Phone: 989-275-7135
Fax: 989-275-3170

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