Forest Pests: Insects, Diseases & Other Damage Agents

Juniper Webworm (Dichomeris marginella)

Maier, C.T., C.R. Lemmon, J.M. Fengler, D.F. Schweitzer, and R.C. Reardon. 2004. Caterpillars on the Foliage of Conifers in the Northeastern United States. FHTET-2004-1. Morgantown, WV: USDA Forest Service, Forest Health Technology Enterprise Team; 151 p.

Description. Very light brown body with dark middorsal and subdorsal stripes. Brown head; orange-brown prothoracic shield with light anterior margin and with narrow, dark brown spot at hind margin. Brown middorsal stripe narrower than dark brown subdorsal stripe. Up to 14 mm.

Food. Common and creeping junipers.

Life Cycle. One generation. Partly grown caterpillar overwinters in a silken case in the webbed foliage. Mature caterpillar present in May and June.

Comments. After hatching, the young caterpillar mines foliage. The mature caterpillar hollows needles while it dwells in a communal web of dead needles and frass (see below). It forms a pupa in a silken cocoon in the webbed foliage. The juniper webworm also infests non-native junipers that are used in landscaping. This introduced species is native to Europe.

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