Gypsy Moth Press Release

Sauk County is seeing a steady increase in Gypsy Moth populations as this latest invasive species continues to extend its range to the west. The first severe outbreaks were found in Rocky Arbor, Devil's Lake and Mirror Lake state parks where spraying programs to reduce populations have been performed the last two years. “It does make sense that the first high populations were found in these parks,” explains Joe Van Berkel, Gypsy Moth Coordinator for Sauk County . “The Gypsy Moth depends on humans to extend its range. The female moths don't fly so they lay their eggs right where they mate and the hatching caterpillars have only a limited range of movement. Their big move comes when campers, boats, fire wood or other items, with their attached egg masses, are moved from an infested area. If that camper is at Devil's Lake in May when the caterpillars hatch - it's perfect for them. There is a whole new forest to devour.”

The average egg mass hatches over 500 caterpillars. In the eastern part of the state, there are entire 40-acre wooded parcels stripped by the caterpillars. The feeding does not kill the trees directly but can weaken the trees so severely that they become vulnerable to other diseases that can kill them. The caterpillar feeding can also cause quite a mess with droppings on lawn furniture and picnic tables underneath shade trees.

Sauk County is now starting to see increased populations in areas outside the parks. Merrimac along Lake Wisconsin , the Baraboo Bluffs west of Baraboo and the Lake Buckhorn area between Reedsburg and Baraboo have reported high populations. “The same state-sponsored spray program used in the parks is available to landowners,” explains Van Berkel. To be eligible an area must have a minimum population of egg masses, have 50 percent tree canopy, and be at least 20 acres in size. The best time to sample for egg masses is after the leaves drop. The tan wooly egg masses will be found on the underside of branches, often high in the trees, so binoculars may be necessary. If you can count 25 egg masses in a 30-foot diameter circle, you are probably near the threshold number to qualify. If you take three random samples in a 20-acre forest and they all exceed this count, call to have a county staff person verify your number.

If a forest qualifies, the County will assist with an application for a spray block. The DNR approves all spray blocks and then recruits bids to spray these blocks in spring 2010. The cost of spraying is the responsibility of the landowner. However, the cost generally falls under $40 per acre, well under the going rate for private applications. The state does attempt to get federal cost sharing to reimburse half of the cost, but there is no guarantee of these funds.

The spray is composed of a bacterial insecticide, Bacillus thuringiensis kurstakii. The bacteria is sprayed onto leaves in early June and then eaten by the caterpillars. Once ingested it kills the caterpillars by disrupting their digestive system. The bacteria does harm other caterpillars also so it is only used when the population of Gypsy Moths is at nuisance levels.

To learn more about the program or how to do an egg count, check out the website gypsymoth.wisconsin.gov. If you have high egg mass counts, call the Land Conservation Department at 355-3245 for verification. All affected sites need to be reported to the Land Conservation Department before November 12 to qualify for the program.