Fall Webworm

🔬

PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

Illustrated identification guide — PestControlBasics.com

🔍 Identification

Webs: 1-3 feet across; at branch tips (not inside branches like tent caterpillar); contain 100-400 larvae plus their excrement and partially eaten leaves. Larvae: 25-35mm; pale yellow-green to tan with dark spots; tufts of hair. Adults: white moths with occasional black spots. Found on: 90+ tree species — walnut, cherry, crabapple, ash, elm, and many others — in late summer.

🧬 Biology & Behavior

Fall webworm differs from eastern tent caterpillar — tent caterpillar: spring, crotch of branches, inner nest. Fall webworm: late summer, branch tips, enclosing leaves inside web. Healthy mature trees tolerate complete fall webworm defoliation without mortality — they've already completed most of the growing season's photosynthesis. Young trees and trees stressed by drought may be more affected.

⚠️ Damage & Health Risk

Aesthetic damage from unsightly webs; leaf consumption from August-October (after most of the season's growth is complete); occasional significant defoliation of young trees in heavy infestation years.

🔧 DIY Treatment

Physical removal — cut off the infested branch tip and bag or burn webs with larvae inside. Bt kurstaki spray into open web ends kills larvae. For valuable small trees: spinosad spray is effective. Tolerance is appropriate for healthy mature trees.

👷 When to Call a Pro

Rarely warranted for healthy mature trees.

❓ FAQ

Will fall webworm kill my tree?

Healthy mature trees almost never die from fall webworm defoliation — the timing (late season) means most of the year's photosynthesis has already occurred. Young trees (under 5 years) and drought-stressed trees are more vulnerable. Removing web clusters by pruning and physical removal is usually sufficient management for valuable young trees.

Is fall webworm the same as tent caterpillar?

No. Eastern tent caterpillar: spring (April-May); builds silken nest in V-junction of branches, not at tips; dark caterpillars with blue spots and white stripe. Fall webworm: late summer (August-October); builds web enclosing branch tips and leaves; pale caterpillars. Different species, different timing, different web location.

Factor	Details
U.S. Range	All or most U.S. states
Regional Detail	Distribution varies — consult your local extension service for regional prevalence data.

Factor

Details

U.S. Range

All or most U.S. states

Regional Detail

Distribution varies — consult your local extension service for regional prevalence data.

📅 Treatment Timing Guide

Treating at the right time dramatically improves results. Pest control timed to the life cycle uses less product and achieves better long-term control.

Period	Action
Spring	Inspection and perimeter treatment before pest season starts.
Summer	Active monitoring and targeted treatments as needed.
Fall	Preventive treatment before overwintering pests seek entry.

Period

Action

Spring

Inspection and perimeter treatment before pest season starts.

Summer

Active monitoring and targeted treatments as needed.

Fall

Preventive treatment before overwintering pests seek entry.

💰 Professional Treatment Costs

Service Type	DIY Cost	Professional Cost
Initial inspection	Free (self-inspect)	$75–$150 (often credited to treatment)
One-time treatment	$30–$100 in materials	$150–$500
Annual service contract	N/A	$400–$900/year
Severe infestation	Often ineffective alone	$500–$2,500+

Service Type

DIY Cost

Professional Cost

Initial inspection

Free (self-inspect)

$75–$150 (often credited to treatment)

One-time treatment

$30–$100 in materials

$150–$500

Annual service contract

N/A

$400–$900/year

Severe infestation

Often ineffective alone

$500–$2,500+

Prices vary by region, property size, and infestation severity.

❓ Common Questions About 🐛 Fall Webworm

How do I confirm I actually have this pest (not something similar)?

The most reliable confirmation is a physical specimen — capture one and compare to reference images on this page. For cryptic pests (bed bugs, termites), look for secondary signs: frass, shed skins, mud tubes, or bites with a specific pattern. When uncertain, a professional inspection is faster than months of misidentification.

Can I treat this myself or do I need a professional?

DIY is effective for small, accessible infestations caught early. Professionals are worth the cost when: the infestation is inside wall voids or structural elements, multiple rooms are affected, you have health-risk pests (hantavirus, venomous species), or DIY has already failed twice.

How long until the infestation is completely gone?

Expect 3–8 weeks for most infestations with proper treatment. Insects with dormant life stages (pupae, eggs) extend the timeline because those stages are impervious to most insecticides. Follow-up treatments at 2 and 4 weeks catch each new cohort as they emerge.

What's the most common mistake people make treating this pest?

Treating only the visible pest population while ignoring the harborage site, entry point, or breeding location. Killing adults provides temporary relief but the population rebuilds from hidden egg cases, pupae, or new arrivals through unaddressed entry points.

🐛 Fall Webworm