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How to Manage Pests
UC Pest Management Guidelines
Almond
Tent Caterpillars
Scientific names:
Forest tent caterpillar Malacosoma disstria
Western tent caterpillar: Malacosoma californicum
(Reviewed 1/05,
updated 1/05)
In this Guideline:
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Tent caterpillars overwinter in the egg
stage; eggs give rise to destructive caterpillars in spring and early
summer. Forest tent caterpillars are
grayish with yellow stripes along the side, separated by a broad blue stripe.
There is a row of white, keyhole-shaped spots on the back. Colonies build a mat
of webbing and move out from it to feed.
Western tent caterpillars are
widespread in California but seldom seen in almond orchards. Their larvae are
hairy and dull yellow-brown with rows of blue and orange spots on top of the
bodies. Colonies of this caterpillar build silk tents around branch crotches
and feed outside the tents. There is one generation each year.
Damage caused by tent caterpillars may be serious on individual trees and along
orchard edges, but is usually randomly scattered throughout the orchard. Young
orchards are usually the most severely affected. In April and June,
caterpillars build large silken tents over leaves on which they are feeding,
they do not eat leaf veins and damaged leaves are skeletonized. Another closely
related species, commonly found in foothill areas, causes similar damage but
does not produce the silken webbing.
On small trees, infested twigs may be cut out and destroyed. Spray programs for
other insects generally reduce populations. If insecticide treatments are
required, localized treatments on individual trees and branches are generally
all that is necessary. Treat when small caterpillars are first observed.
Populations usually decline naturally due to disease.
| Common name |
Amount/Acre** |
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| (trade name) |
(conc.) |
(dilute) |
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A. |
BACILLUS THURINGIENSIS ssp. KURSTAKI# |
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(various products) |
Label rates |
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COMMENTS: Best when applied to small larvae. |
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UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431
Insects and Mites
F. G. Zalom, Entomology, UC Davis
C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
R. L. Coviello, UC Cooperative Extension, Fresno Co
R. A. Van Steenwyk, Insect Biology, UC Berkeley
M. W. Freeman, UC Cooperative Extension, Fresno Co.
Acknowledgment for contributions to the insects and mites section:
R. E. Rice, Kearney Agricultural Center, Parlier
L. C. Hendricks, UC Cooperative Extension, Merced Co.
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