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Prune

Monitor for Leafrollers and Other Caterpillars

Bloomtime applications of Bacillus thuringiensis for peach twig borer help to keep leafroller and other caterpillar populations under control. Leafroller damage is not a problem for prunes grown for the dried market, but needs to be monitored on fresh market prunes so that prompt action can be taken if damaging populations develop.

Monitor for the presence of caterpillars from the beginning of bloom (green fruitworm) through petal fall (leafrollers), looking for any species that may cause fruit damage. Carefully check young leaves and shoots for the presence of peach twig borer and leafroller larvae and leaf damage. Use a beating tray to catch green fruitworm larvae that drop from the tree as you shake blossom clusters.

Use the photos below to identify caterpillars that are present in the orchard at this time of year. Names link to more information on identification and management.

Click on photos to enlarge
Larva of peach twig borer.
Peach twig borer
Identification tip: Darker body segments give older larvae a distinctive ringed appearance.
Young fruittree leafroller larva.
Fruittree leafroller
Identification tip: Green larva with dark head, hangs from silken thread when disturbed.
Larva of obliquebanded leafroller.
Obliquebanded leafroller
Identification tip: Yellowish-green larva with brown head, hangs by thread when disturbed, difficult to distinguish from fruittree leafroller.
Speckled green fruitworm larva.
Green fruitworms
Identification tip: Green larva with pale-green head and several white lines on sides and back.
Larva of western tussock moth.
Western tussock moth
Identification tip: Colorful prominent tufts of hair.
Larva of the spring cankerworm, Paleacrita vernata.
Cankerworms

Identification tip: Green larva with green head; only two prolegs—moves in inchworm fashion.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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Agriculture and Natural Resources, University of California

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