How to Manage Pests
UC Pest Management Guidelines
Scientific Name: Hyphantria cunea
(Reviewed 12/07, updated 3/11)
In this Guideline:
DESCRIPTION OF THE PEST
Larvae of the fall webworm are pale brown or gray
caterpillars. Their bodies are covered with long white hairs arising from black
and orange spots. Fall webworms spend the winter as pupae. Moths emerge in late spring and lay eggs that
hatch into caterpillars in late summer. There is one generation each year.
From July to September, fall webworm caterpillars can be found forming silken
skeletonizing leaves, leaving behind only leaf veins.
On small trees, infested twigs may be cut out and destroyed.
Insecticide sprays applied for other pests often keep these leaf-eating
caterpillars in check. If insecticide treatments are required, generally all
that is necessary are localized treatments on individual trees applied when
evidence of caterpillars is first observed. Spray must penetrate silken tents
for effective control.
Sprays of Bacillus
thuringiensis are acceptable for use in an organically certified crop.
||Amount to Use**
|When choosing a pesticide, also consider
information relating to impact
on natural enemies and honey bees as well as environmental impact.
||MODE OF ACTION GROUP NUMBER1: 28
||COMMENTS: Larvicide. The best timing is to
apply before egg hatch. Do not
apply more than 0.2 lb a.i. (9 oz)/acre/year. Do not make more than four
applications per year. To reduce
the development of resistance do not make more than three consecutive
applications of any Group 28 insecticides (anthranilic diamide) per generation per season.
||BACILLUS THURINGIENSIS ssp. KURSTAKI#
||MODE OF ACTION GROUP NUMBER1: 11.B2
||COMMENTS: Most effective on small caterpillars. Does not destroy natural enemies.
UC IPM Pest Management Guidelines:
UC ANR Publication
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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