New Name, Old Foe; Battling Spongy Moths at Big Hill Park

Last summer, Rock County Conservationist volunteers noticed several trees near the Center were showing signs of stress and leaves were disappearing at an alarming rate. Closer inspection revealed that gypsy moth (Lymantria dispar) caterpillars were hatching and working their way up the tree trunks to consume all the leaves of many varieties of trees.

Left: spongy moth egg mass on a Big Hill tree; Right upper: spongy moth life cycle: Right lower: trees in the Big Hill entry tagged as having egg masses. 

Well, these invasive pests are back. They are going after Big Hill trees indiscriminately, but sporting a new name, thanks to the Entomological Society of America: Spongy Moth. Spongy refers to the appearance of the egg masses that are nestled into the tree’s bark, and can overwinter to produce the next spring’s moths. Not only does this new name eliminate the slur of the old, but better aligns with its name in other languages (In French: la spongieuse, in German: schwammspinner-sponge spinner).

You may have noticed yellow tape wrapped around many trunks in the Park entryway. These are trees that have been identified by these intrepid RCC volunteers and they have been marking candidates for removal (especially if the tree is dead or invasive–such as buckthorn or siberian elm), or treatment. The wood with the sacs will need to be chipped or burned, so the larvae are prevented from hatching. Large, native trees can be treated with a spray that will kill the eggs, but not harm the tree. 

If you want to learn more, see: Wisconsin Spongy Moth Portal. It has info about where the DNR conducts sprays, but also treatment options for homeowners outside the spray area and other suggestions for how to deal with this pest.