How to Manage Pests

UC Pest Management Guidelines

Alfalfa

Webworm

Scientific Name: Loxostege spp.

(Reviewed 11/06, updated 11/06)

In this Guideline:


DESCRIPTION OF THE PEST

Webworms are dark green caterpillars with two white stripes and black spots on their backs. They are often found within webbed leaves. They vary in size up to almost 1.5 inches in length.

Webworms overwinter as larvae in the ground adjacent to their fall food host. Moths emerge in early spring and lay eggs on leaves of host plants. Larvae will feed for 3 to 5 weeks.

DAMAGE

The larval stage feeds inside of webbed leaves on the upper parts of the plant in summer and fall. If numbers are abundant, this webbing will be clearly visible and will cover extensive areas of foliage.

MANAGEMENT

Early cutting may give satisfactory control. Treatment is rarely justified in California.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Alfalfa
UC ANR Publication 3430

Insects and Mites

  • C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
  • L. D. Godfrey, Entomology, UC Davis
  • M. Rethwisch, UC Cooperative Extension, Riverside County (Blythe)
  • D. R. Haviland, UC Cooperative Extension, Kern County
  • P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier
  • R. F. Long, UC Cooperative Extension, Yolo County

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