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Garden Webworm

Achyra rantalis[4]

The garden webworm is a small, spotted caterpillar that ties leaves together with silk and feeds inside, skeletonizing beans, alfalfa, many vegetables and weeds; badly damaged plants end up covered in webbing.[1][2][3]

Group
Insect
Order
Lepidoptera
Family
Crambidae
US records
36 states
Sources
4 cited
Updated
2026-10-17
Adult garden webworm moth, tan to orange-brown with darker markings, resting on a wall
Adult garden webworm moth, tan to orange-brown with darker markings, resting on a wall. (c) Mary Beth Stowe, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Caterpillars are yellow-green to green with a yellow-brown to orange mottled head, a pale stripe down the middle of the back and six black spots on each abdominal segment, three on each side in a triangle, each with stiff hairs.[1][2][3]
  • Missouri gives the full-grown length as 0.5 to 0.75 inch; the Crop Protection Network and the Northern Plains guide say about 1 inch.[1][2][3]
  • Look for leaves tied together with silk webbing, with the caterpillars feeding inside the shelter.[2][1]
  • The adult moth is yellowish brown with irregular grayish markings and a wingspan of about 3/4 inch.[3]

Look-alikes

Look-alikeHow to tell them apart
Alfalfa webwormA very similar caterpillar that also webs leaves on alfalfa and soybeans; its six spots per segment are less distinct, and its moth is slightly larger.[2][3]

Where it lives

Native to North America and found in gardens, field crops and weedy areas; in the Northern Plains it overwinters as pupae in the soil, while in warmer Gulf Coast states it may overwinter as caterpillars.[3][1]

US map: public records from 36 states since 1990 (GBIF).

Biology and life cycle

Adults emerge and mate in spring; the eggs hatch in 3 to 7 days, and the caterpillars feed on the undersides of leaves for about three weeks, spinning silk webbing, before they pupate.[3]

Caterpillars are present from late spring to fall, with two to three generations a year in Missouri.[1]

Damage and signs

  • Host plants include many vegetables, field crops such as alfalfa and soybeans, and weeds; the caterpillars often move into soybeans when nearby alfalfa is cut.[1][2][3]
  • Feeding skeletonizes the leaves, and severely damaged plants are covered with silken webbing.[1][3]

Health risk

It feeds only on plants; none of the sources reports any harm to people or pets.[1][3]

Control

Prevention

Keep an eye on plantings next to weedy areas or recently cut alfalfa, where webworms are most likely to move in.[2][3]

Pesticides

The Crop Protection Network refers growers to their local extension specialist for current treatment recommendations; follow the label of any product used.[2]

Common questions

What is webbing the leaves of my beans together?
Small green caterpillars with rows of black spots feeding inside silk-tied leaves are likely garden webworms.[1][2]
Where do garden webworms come from?
They often move in from weedy areas and nearby alfalfa, especially after the alfalfa is cut.[2][3]

Sources

  1. University of Missouri Extension, “Caterpillars in Your Yard and Garden (IPM1019), page 18: garden webworm.” extension.missouri.edu/publications/ipm1019/18 (accessed 2026-10-17)
  2. Crop Protection Network (multi-state university extension collaboration), “Webworms in Soybean.” cropprotectionnetwork.org/encyclopedia/webworms-in-soybean (accessed 2026-10-17)
  3. Northern Plains IPM Guide (hosted on Bugwood wiki), “Webworms on soybean (Northern Plains Integrated Pest Management Guide; B. Hadi, J. Knodel, K. Ostlie, R. J. Whitworth, J. P. Michaud, P. E. Sloderbeck).” wiki.bugwood.org/NPIPM:Webworms_on_soybean (accessed 2026-10-17)
  4. iNaturalist, “Achyra rantalis taxon page (order and family).” www.inaturalist.org/taxa/204077 (accessed 2026-10-06)

Updated 2026-10-17. Built from sourced records. Spot an error? Tell us.