NC State Extension Publications

Description and Biology

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The ailanthus webworm, Atteva aurea, is the immature stage of an ermine moth, a small (1/2 inch), yellow-orange insect traversed by four blue-black bands marked with conspicuous white spots on the wings. The wings are held tight against the body when not in flight. Ailanthus webworms are slender, brown to almost black, and sometimes have four white dots on the top of each segment. The head is noticeably lighter in color and may also have white spots. Some thin white and olive-green stripes might show along each side of the abdomen. They spin a frail silken web on the leaves of ailanthus. Moths mate in the morning, and female moths lay their eggs in the webbing usually in the evening. When mature, webworms molt into pupae that are also suspended in the loose webs. The caterpillars remain in the web during the day, but leave it to feed at night. During the growing season, all stages may be found in a web. Development from egg to moth takes about a month, so we have several generations per year in North Carolina. Eggs overwinter and hatch in mid to late spring.

Ailanthus webworm moth

Ailanthus webworm moths are brightly marked.

yellow-orange of this ailanthus webworm moth

The yellow-orange of this ailanthus webworm moth clashes with the pink sedum flowers completely disrupting the feng shui of this otherwise lovely photo.

Typical ailanthus webworms.

Typical ailanthus webworms.

This ailanthus webworm

This ailanthus webworm is pale perhaps because it recently molted.

Ailanthus webworms pupate in their webbing.

Ailanthus webworms pupate in their webbing.

Host Plants

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Although Ailanthus trees have a wonderful common name (tree of heaven), in North Carolina they seem to be more of a weed tree growing in vacant lots and in cracks in pavement. The ailanthus webworm also infests paradise tree, Simarouba glauca, as well as Simarouba amara. Adults are considered good pollinators as they visit many species of flowers during the daytime.

Ailanthus webworms loosely tie leaves together with silk strands

Ailanthus webworms loosely tie leaves together with silk strands.

ailanthus webworm webs

By mid summer, ailanthus webworm webs can be large and messy.

Residential Recommendations

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The ailanthus webworm has not been reported to be resistant to insecticides. Most of the insecticides labeled for landscape use found in the garden sections of big box stores should give more than adequate control.

Other Resources

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For assistance with a specific problem, contact your local Cooperative Extension center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology & Plant Pathology

Find more information at the following NC State Extension websites:

Publication date: March 11, 2019
Revised: Aug. 29, 2019

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