Caterpillars force temporary closure of Wisconsin state park

June 19, 2007 A park in the U.S. state of Wisconsin has been closed, due to being over-run by gypsy moth caterpillars.

The Wisconsin Department of Natural Resources (DNR) announced the unprecedented move yesterday, with officials saying they would temporarily close Rocky Arbor State Park near Wisconsin Dells due to an infestation of gypsy moth larvae.

The larvae are present at the park in such large numbers that, according to a report by the Wisconsin State Journal, camping there would "apparently be a squishy, nightmarish experience."

Mark Guthmiller, DNR gypsy moth suppression coordinator said that "there are also health and safety considerations that prompted our action," explaining that there was a significant risk of people having severe allergic reactions to the caterpillars. There were also concerns that the caterpillars might be accidentally transported out of the park on park user's vehicles to areas where the moths have as yet failed to establish themselves. Guthmiller also commented that related sanitation issues" would also "significantly detract from the quality park camping experience."

Andrea Diss-Torrance, another gypsy moth coordinator for the DNR, said of the infestation: "It's very severe - it's as severe as I have ever seen." The closure, which will run until at least June 27, is thought to affect around 95 campground reservations at the site, which covers 255 acres. State officials have been attempting to arrange alternatives for campers at nearby parks, or, failing this being acceptable, are offering refunds. The park will be closed until after the caterpillars have completed pupation - the period in their life cycle in which they transform into moths.

The gypsy moth is a pest in the U.S., having been introduced in the 19th-century in a failed attempt to to try to breed a hardy variant of silkworm. The moths can strip the leaves off at least 250 different tree species, and as they lack natural predators in the U.S., cause significant damage. The moths often chew leaves but don't actually eat them, thus increasing the potential damage.

At Rocky Arbor, they have already stripped all the trees in some areas of the park. The caterpillars can kill trees directly, but more usually weaken them so that they are more susceptible to die from other causes, such as disease.