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How to Manage Pests
UC Pest Management Guidelines
Walnut
Fruittree Leafroller
Scientific name: Archips
argyrospila
(Reviewed 12/07,
updated 4/09)
In this Guideline:
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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.
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.
No controls are recommended, however first generation treatment of
codling moth will kill fruittree leafroller caterpillars.
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UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471
Insects and Mites
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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