By Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665
Webbing and a collection of frass (caterpillar excrement) around these cones is the web nest of pine webworm. / Photo Credit: Wisconsin DNR
Pine webworm (Pococera robustella) is a native moth whose caterpillars feed on pine needles. In Wisconsin, the caterpillars prefer young jack pine and red pine. A single generation per year occurs in Wisconsin.
Young larvae mine needles, feeding within the needle. Older larvae form a compact web that they fill with small, oval pieces of frass. In early fall, the larvae drop to the ground to pupate and spend the winter.