Wisconsin DNR announces 2024 spongy moth aerial spray plans

Wisconsin Ag Connection - The Wisconsin Department of Natural Resources (DNR) has announced its plan to combat spongy moths with aerial spraying on six properties totaling 928 acres. The targeted areas are in Columbia, Marinette, Sauk, and Walworth counties and contain valuable trees within state parks and forests.

The spraying will use Foray, a bacteria-based insecticide, applied between early May and early June. Exact timing depends on caterpillar development and weather. The DNR aims to avoid spraying during Memorial Day weekend on high-use properties.

Residents near the spray zones will be notified beforehand. Updates and details are available on the DNR website, where visitors can sign up for email alerts. A hotline (1-800-642-MOTH) also offers information on spraying schedules.

Spongy moth caterpillars can defoliate trees, potentially leading to their death. Outbreaks occur every 5-10 years. In 2023, a record 375,000 acres were affected in Wisconsin. Healthy trees can usually recover from one defoliation event, but repeated defoliation or additional stressors can increase mortality risk.

The DNR program complements the Department of Agriculture, Trade and Consumer Protection's (DATCP) Slow the Spread program targeting western Wisconsin counties. This program uses aerial application to treat low-level spongy moth populations and slow their westward spread.

DATCP uses either the same insecticide as the DNR or a mating disruptor to prevent moth reproduction.

The state does not offer cost-sharing for private property spraying. Landowners interested in organizing aerial sprays can find guidance in the DNR's "Organizing an Aerial Spray for Forest Pests" document.

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