Fall Webworms – What are they?
Introduction
If you’ve ever looked up in late summer or early fall and seen big, silky webs draped over the ends of tree branches, you’ve probably met the fall webworm (Hyphantria cunea). They’re one of the most common tree pests across the United States, and while their presence looks alarming, they’re usually more of a cosmetic nuisance than a 💀 sentence for your trees.
What Are Fall Webworms?
Fall webworms are the caterpillar stage of a white moth. Unlike tent caterpillars — which build their webs in branch crotches in the spring — webworms build their webs at the ends of branches and do their damage in late summer and fall.
They’re not picky eaters, either. Webworms attack more than 90 species of trees, but their favorite hosts include:
- Pecan
- Mulberry
- Sweetgum
- Persimmon
- Hickory
- Oak
Life Cycle and Behavior
The adult moth lays clusters of eggs on the underside of leaves in midsummer. Within a week, tiny caterpillars hatch and immediately begin spinning silk, enclosing leaves at the tips of branches. As they grow, the caterpillars expand the web outward to cover more leaves, creating large, unsightly nests.
Inside the web, dozens or even hundreds of caterpillars feed on leaves, leaving behind only skeletonized midribs and veins. By late fall, the caterpillars drop to the ground, pupate in leaf litter or soil, and re-emerge as moths the next summer.
Do Webworms ‘UNALIVE’ Trees?
Here’s the good news: fall webworms rarely mortally damage trees.
- Healthy, established trees can withstand partial defoliation late in the growing season without long-term damage.
- However, repeated infestations year after year can weaken already stressed trees, making them more vulnerable to secondary pests and diseases.
- Young or newly planted trees may also suffer more if heavily defoliated.
In other words, fall webworms are more of a quality-of-life problem for your tree — and your yard — than a fatal one.
How to Manage Fall Webworms
If you can’t stand looking at the webs, you’ve got options. The key is timing and method:
- Mechanical Control
- Tear open webs with a long pole or rake to expose caterpillars to birds and natural predators.
- Small, infested branches can be pruned out and destroyed.
- Biological Control
- Sprays containing Bacillus thuringiensis (BT) are effective on young caterpillars. BT is safe for people, pets, and beneficial insects.
- Timing is critical: apply when caterpillars are small and actively feeding.
- Natural Predators
- Birds, wasps, and predatory insects all feed on webworms. Simply opening up the webs can allow nature to take its course.
- Chemical Control (Last Resort)
- Broad-spectrum insecticides are rarely necessary and can harm beneficial insects. Reserve them for severe infestations where other methods have failed.
Prevention and Long-Term Care
While you can’t stop moths from laying eggs, you can improve your trees’ ability to withstand infestations:
- Keep Trees Healthy: Water during dry spells, mulch properly, and avoid over-pruning.
- Encourage Natural Enemies: Avoid unnecessary pesticide use that kills beneficial insects.
- Monitor Annually: Early detection makes management easier.
Closing Thought
Fall webworms are like the messy houseguests of the tree world — they show up late, make a visible mess, but usually don’t do lasting damage. With a little management and a focus on overall tree health, you can keep your trees looking good and thriving.
👉 Want to know if your trees need treatment or just patience? Book a digital consultation with me at ArboristOnDemand.com and get professional guidance tailored to your trees.
My Best,
Matt Latham
ISA Board Certified Master Arborist #TX-3737B
ASCA Registered Consulting Arborist #859
ASCA Tree & Plant Appraisal Qualified
409.995.7940 | www.arboristondemand.com
