Hyphantria cunea

Late last week, I came across a nest of early instar, first-generation Fall Webworms (Hyphantria cunea, family Erebidae) on a boxelder (Acer negundo) in southwest Ohio. We see two generations in Ohio, sometimes three in the southern part of the state.

Jim Downs (Forestry Field Specialist, OSU Extension) is reporting a localized Fall Webworm (Hyphantria cunea, family Erebidae) outbreak in Logan County, OH. The heavy infestation was first observed and reported to Jim by Jacob King (ANR Extension Educator/LCSWD Educator, OSU Extension, Logan County).

Participants in the OGIA-OSU Diagnostic Walk-About held this past Monday at the Cincinnati Botanical Garden and zoo found a second generation Fall Webworm nest. The webworms were the black-headed biotype, but more on that later.

Yesterday, I came across a small Fall Webworm (Hyphantria cunea, family Erebidae) nest on a Callery pear (Pyrus calleryana) in southwest Ohio. The webworms were the black-headed biotype, but more on that later.

Fall Webworms (Hyphantria cunea, family Erebidae) have been virtual no-shows over much of Ohio this season. Although, there are reports of highly localized populations with noticeable nests, trees in much of the state are largely free of silk webbing.

This is the second posting on Fall Webworm this season. The first Alert posted on July 27 noted that fall webworm nests are late, but on the rise. However, several significant developments have occurred since that time.

Fall Webworm (Hyphantria cunea, family Erebidae) nests are becoming noticeable in southwest Ohio. Their arrival seemed to be unusually late this season until close inspections revealed the nests are housing the red-headed biotype. But more on that later.

Fall Webworm (Hyphantria cunea) has two overlapping generations per season in Ohio. The "fall" in the webworm's common name is based on the moth caterpillars becoming more apparent late in the season due to larger second-generation nests than those produced by the first generation.

Overwintered fall webworm (Hyphantria cunea) eggs have hatched in southwest Ohio and first-generation nests are becoming noticeable. Look for these hairy caterpillars inside small silk nests enveloping just a few leaves. The nests will rapidly expand over the next few weeks to include more leaves and become far more evident.

Fall Webworm (Hyphantria cunea) has two overlapping generations per season in Ohio. The "fall" in the webworm's common name is based on large second-generation nests normally appearing late in the season. However, we are receiving reports that where localized webworm populations are high, the caterpillars are already producing some truly spectacular nests sometimes enveloping entire trees.