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Past Articles Library | Organic Pest Control | Fall Webworm


(Hyphantria cunea)

Fall webworms are native to North America and are one of the few American insect pests that have been introduced into Europe and Asia. They will build their unattractive silken nests near branch tips and feed voraciously on the foliage within their enclosed area.



Adults are pure white moths with 2 to 2 1/2 inch (5 to 6 cm) wingspans which vary from no spots, to heavy grayish-brown spotting on the forewings, and one to two blackish spots on the hindwings. The abdomen is yellow with black spots. Larvae are beige, covered with dense yellow to brown hairs, and have tufts of long white hairs on their sides.



Fall webworms pupate overwinter in tightly woven cocoons under soil debris or tree bark. Adults emerge in May to June and lay eggs in masses covered with hairs on the undersides of leaves. The eggs hatch in a few days. Groups of larvae feed together through June and July (4 to 6 weeks) inside the web, which extends as the foliage inside is eaten. The last-stage larvae wander all over the tree, then pupate in soil debris. Expect one or two generations per year.




Many deciduous, forest, shade, fruit trees and shrubs. Preferred host plants include hickory (Carya), walnut (Juglans), birch (Betula), ash (Fraxinus), oak (Quercus), cherry (Prunus), and crabapple (Malus).




Damage to the host plant is primarily aesthetic, since leaves are usually eaten late in the season when it is not normally a threat to the health of the tree. Larvae chew on leaves and spin large, unsightly, dirty white webs over the ends of branches; sometimes several branch tips are enclosed by one web.




1. Attract native parasitic wasps with nectar or pollen plants.


1. Prune and destroy branches with webs.

2. Catch larvae in sticky tree bands as they leave to pupate.

3. Spray BTK (Bacillus thuringiensis var. kurstaki**) on leaves around web while larvae are small or when older larvae start wandering outside their web to feed.

**Note: Bacillus thuringiensis should be used with extreme care and used only when prevention and milder control measures don't work since it will kill butterfly larvae as well as pest caterpillars. Apply just around the areas where the known pests are thriving.


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