How to Manage Pests

UC Pest Management Guidelines

Walnut

Fruittree Leafroller

Scientific name: Archips argyrospila

(Reviewed 12/07, updated 4/09)

In this Guideline:


DESCRIPTION OF THE PEST

The fruittree leafroller overwinters in the egg stage on limbs. The eggs are laid in masses on limbs and twigs and are covered with a gray secretion that turns white upon aging. Eggs hatch in early spring. Larvae are green with black heads and are about 1 inch long when fully grown. The intensity of the green color varies from a light green in young larvae to a darker green as they mature.

Adult moths emerge in June or July and deposit overwintering eggs. Adult moths are about 0.5 inch (12 mm) long, with rusty brown wings marked with areas of white and gold. When at rest the adults appear bell shaped and have dark brown bands running at oblique angles across their wings. The wings are mottled with gold and white flecks. There is one generation each year.

DAMAGE

Larvae may enter young walnuts and devour the kernel. By May, the damaged nuts are dry and collapsed with large slotlike holes. The number of nuts attacked is usually insignificant and rarely requires control measures.

MANAGEMENT

No controls are recommended, however first generation treatment of codling moth will kill fruittree leafroller caterpillars.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471

Insects and Mites

  • C. Pickel, UC IPM Program/UC Cooperative Extension, Sutter/Yuba counties
  • J. A. Grant, UC Cooperative Extension, San Joaquin County
  • W. J. Bentley, UC IPM Program/Kearney Agricultural Center, Parlier
  • J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
  • W. W. Coates, UC Cooperative Extension, San Benito County
  • R. A. Van Steenwyk, Insect Biology, UC Berkeley
Acknowledgment for contributions to Insects and Mites:
  • W. H. Olson, UC Cooperative Extension, Butte County
  • L. C. Hendricks, UC Cooperative Extension, Merced County
  • G. S. Sibbett, UC Cooperative Extension, Tulare County

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