
Euonymus caterpillars web branches as they feed on the leaves of Euonymus species. / Photo Credit: Wisconsin DNR
By Michael Hillstrom, DNR Forest Health Specialist
Michael.Hillstrom@wisconsin.gov
Euonymus caterpillars (Yponomeuta cagnagella) made a dramatic appearance in June, webbing and defoliating Euonymus shrubs in several counties.
Multiple species of Euonymus may be attacked, including spindle tree, winged (e.g., burning bush), eastern wahoo, winter creeper and others. Winged euonymus is listed as Restricted in Wisconsin’s invasive species rule NR40.

Euonymus caterpillars feeding on a spindle tree in Dane County. / Photo Credit: Vicky Jones
Euonymus caterpillars were first found in Wisconsin in 1989. Although rarely seen, the damage is very obvious when it occurs. The creamy-white caterpillars with black spots are gregarious and create large amounts of webbing as they feed. Feeding lasts about three weeks, and the caterpillars reach approximately ¾-inch before pupation occurs in June.
Euonymus caterpillars go through one generation per year, so no further damage will occur this year. No management is needed; defoliated shrubs will typically produce new leaves.
Eastern tent caterpillars may also be active during the same time span, but their tents have a different appearance. Also, their feeding is focused on fruit trees.