Spongy Moth Damage Nearing Record Levels News | August 15, 2023 | 0 | by Morgan McCarthy Wisconsin is seeing its worst outbreak of spongy moth caterpillars in over ten years. The Wisconsin Department of Natural Resources says the caterpillars are invasive and can destroy several different species of trees. The DNR says so far this summer spongy moth caterpillars have cause about 370-thousand acres of deforestation in Wisconsin. The last time they did that much damage was 2010.