Native to China, the mimosa webworm (Homadaula anisocentra) is a defoliating caterpillar in the order Lepidotera.  It was first detected in the United States on mimosa in 1940.  Mimosa webworm larvae cause unsightly damage by spinning webs around foliage and feeding on the leaves, skelotonizing them. 

Damage is most noticeable in mid-summer from the damage of the second generation.  Complete defoliation may occur if larvae are undetected, which could lead to eventual tree death.  Larvae may also be a nuisance in late summer as they climb on houses or other structures in search of locations to over winter.  

Susceptible Hosts
Mimosa (Albizia julibrissin) and honeylocust (Gleditsia triacanthos).

Pest
Homadaula anisocentra

Symptoms
* The under surface of the leaves are destroyed first as the larvae begin to feed.
* By late summer and early fall, entire leaves are stripped except for the larger veins and midribs, skeletonizing them.
* On mimosa, the leaves turn a dull gray before dying.  Honey locust appear brown or as if they were scorched by fire.

Signs
* Eggs are very small, oval, white, and deposited on the leaves.  Eggs will turn pink close to hatching.  Larvae are scattered throughout the tree forming webs around leaves and flowers from which they feed.
* Larvae are ½’ – 1” long, vary in color from gray to brown with a tint of pink, and have five white stripes running longitudinally along the body.
* Larvae are very active.  When disturbed they twitch violently and drop from silk strands.
* The small, silvery adult moth is rarely seen, but has a wings covered in black dots, and a wingspan of ½”.

Life Cycle
* Moths of the first generation appear in late spring and deposit their eggs on leaves.
* Eggs hatch soon after being laid and larvae begin spinning their silken web from which they feed through midsummer.
* In midsummer first generation larvae drop to the ground on silken threads to pupate in bark cracks or ground cover.
* Second generation moths appear in mid to late summer, lay eggs, spin webs, feed, and pupate.  This generation causes the most damage.
* Pupae of the second generation over winter in bark cracks on ground cover.
* The two generations overlap considerably and all stages can be found during the summer.

Distinguish from look-alikes
Proper identification of the host plant, timing of symptoms, and particular marking characteristics are key distinctions between caterpillars.

Distribution
Primarily a pest in the Eastern and Midwestern United States, but was found in CA in the 1960’s.

Management Strategy Summary                           
Trees should be monitored for the earliest signs of feeding in late spring.  Larvae will become more difficult to control as they become larger.  In addition to providing control of mimosa webworm, soil applications of Lepitect will provide control against plantbug (if applied earlier enough in the growing season), bagworm, and honey locust mite.  Apply at least two soil applications at or just prior to full leaf development in the spring to control all of these pests.

University of Kentucky

Penn State

University of Massachusetts

Virginia Cooperative Extension