NC State Extension Publications

Description and Biology

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Mimosa webworms, Homadaula anisocentra, are small (up to one inch long), slender caterpillars that web up the foliage of mimosa and honey locust from June to September or early October. They are grayish to dark brown with five white stripes and are sometimes tinged with rose or pink. When disturbed, these webworms are extremely active and thrash violently before dropping down on silk strands. This pest overwinters inside a white, silken cocoon as a slender brown pupa in mulch, on tree trunks or some other sheltered area on the soil. The following June, small, spotted, silvery gray moths emerge, mate and lay eggs. From these eggs hatch tiny caterpillars that feed and grow to about an inch long. Sometimes mimosa webworms pupate in the webbed leaves or near buildings, paved areas, or even on buildings. Another generation of moths emerges a short time later. The cocoons resemble puffed rice and are often found in groups. We have two to three generations of mimosa webworms a year in North Carolina.

Mimosa webworms are slender and have five white lines.

Mimosa webworms are slender and have five white lines.

Mimosa webworm cocoons

Mimosa webworm cocoons are small and white.

Mimosa webworm moth

Mimosa webworm moths are small, silvery gray, and spotted.

Mimosa webworm egg

Mimosa webworm eggs are extremely tiny and pink.

Host Plants

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Mimosa webworms web up the foliage of mimosa and honey locust. 'Sunburst' honey locust is reported to be very susceptible whereas 'Moraine', 'Skyline', and 'Shademaster' are less so. It is surprising such a small insect can cause so much damage, but heavily infested trees may have every leaf webbed up, skeletonized, and brown by mid summer. Trees ravaged for several years in a row may be severely stunted or may even die.

Mimosa webworms web adjacent leaves

Mimosa webworms web adjacent leaves together and feed within the web.

Mimosa webworms can greatly damage

Mimosa webworms can greatly damage the appearance of honey locust and mimosa.

Residential Recommendations

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Keep leaf and other debris raked up under host trees. If treatment is made in spring while honey locust and mimosa trees are in bloom, it would probably be better to use Bacillus thuringiensis insecticides (Dipel, Thuricide, Biotrol etc.) for control rather than a synthetic organic pesticide to avoid killing bees. Later in the season, those insecticides labeled for residential landscape use should give more than adequate suppression. This pest is a problem wherever honey locust is used as a landscape tree.

References

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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 and Plant Pathology

Publication date: Oct. 3, 2016
Revised: Oct. 4, 2019

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