Sunday, August 2, 2009

Landscape - Fall Webworms

It is the time of the year to see fall webworms on many trees and shrubs. The following is more information.

Fall webworms feed on over 85 species of trees including, walnut, hickory, fruit trees, maples, cherry, and sweetgum. There are two generations in the mid-Atlantic area. Fall webworm overwinter as pupa in leaf litter, old nests, or in crevices found in bark, and emerge sometime in mid to late June. Females lay eggs on the underside of leaves and egg hatch occurs between 802 and 1517 [1105 peak hatch] GDD. The larvae are pale yellow to pale green with black spots along the back. Caterpillars are covered with long white to yellowish colored hairs. The second generation of fall webworm is seen later in the summer with peak egg hatch at 2723 GDD. Physically remove the nests and tear open nests with pruners, or a stream of water from a high pressure hose. Natural enemies such as birds, predatory insects and parasitoids will take advantage of damaged nests. Chemical control if necessary may include B.t., insecticidal soap, spinosad, tebufenozide, diflubenzuron, or a pyrethroid.

Fall Webworm. Photo from the Pennsylvania Department of Conservation and Natural Resources - Forestry Archive,

Information from Brian Kunkel, Ornamental IPM Specialist, UD

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