Native to North America, the fall webworm (Hyphantria cunea) is an insect in the Lepidoptera order found throughout the United States. 

Major damage is rare but this pest is a nuisance because of large, unsightly silken webs found enclosing branch tips in mid to late summer.  By late summer and early fall, entire leaves are stripped except for the larger veins and midribs.  Multiple generations may cause severe defoliation to a tree. 

Susceptible Hosts
The fall webworm attacks almost all deciduous trees.  The more common host trees include pecan and hickory (Carya), walnut (Juglans), birch (Betula), American elm (Ulmus), maples (Acer), persimmon (Diospyros), sweetgum (Liquidambar), willow (Salix), alder (Alnus), sourwood (Oxydendrum), red mulberry (Morus) and all fruit trees.  Conifers are rarely attacked.

Pest
Hyphantria cunea

Symptoms
* In late summer and early fall, entire leaves are stripped except for the larger veins and midribs.

Signs
* Small, yellow to light green egg masses covered in hair may be found on the underside of the leaves.
* Large (sometimes 2 to 3 feet), light gray, silken webs enclosing tips of branches in late summer and early fall.  These webs may persist throughout the winter.
* Mature caterpillars are 1 to 1 ¼ “(25-31mm) long and covered in long, silky hair.
* The caterpillars make rhythmic jerking movements when the nest is disturbed.

*Two races of fall webworm exist, a blackheaded and redheaded race.  The races are different in appearance, biology, and food habits.  
Blackheaded
o Caterpillars are yellow to green with a dark, wide stripe, and two rows of wart-like marks, or tubercles, along the back.
o A yellow stripe lines each side of the caterpillar.
o Long, light colored hairs protrude from the black tubercles.
o The adult females place their eggs in single layers on the underside of the leaves.

Redheaded
o Caterpillars are yellow to tan with orange to reddish wart-like marks, or tubercles, along the back.  
o A yellow stripe lines each side of the caterpillar.
o Long, light colored hairs protrude from the brightly colored tubercles.
o The adult females place their eggs in two layers on the underside of the leaves.

Life Cycle
* Adults emerge spring through summer.
* Females deposit their egg masses on the bottom side of leaves.  Eggs hatch in one to two weeks.
* The young larvae begin to spin their silken webs upon the terminal branches’ foliage they are feeding on during late summer and early fall.  
* Larvae mature in about 6 weeks, leave the web, and pupate in the soil, under loose bark, or leaf litter.
* The fall webworm over winters in a cocoon that is protected in the soil, under loose bark, or leaf litter.  
* 1 to 4 generations per year.

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

Expectations
* Soil injections of Lepitect will begin efficacy within 3-10 days for most pests.   Control on larger trees will not occur as quickly (2-3 weeks).  Lepitect soil applications last for 30 days after treatment.  Repeat applications may be necessary if pest activity persists for longer than 30 days.
* Conserve has a short residual (4-7 days) but is softer on beneficial insects, whereas Up-Star Gold will provide slightly longer residual, but is broad spectrum.
* Use Lepitect Infusible on trees that can’t be treated with a foliar or soil application.  Lepitect Infusible has a 30 day residual.

Other Treatment Practices
* Promote health and vigor with proper irrigation, mulching, proper pruning and prescription based fertilization practices.
* Prune out the nests after they have formed.  Early morning or late afternoon is a good time to do this as most of the caterpillars will be in the nest.

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