How to Manage Pests
UC Pest Management Guidelines
In this Guideline:
Grape leaffolder and western grapeleaf skeletonizer feed on foliage and heavy populations can lead to defoliation. Omnivorous leafroller, orange tortrix, and light brown apple moth feed on leaves, flowers, and developing berries, but their primary damage is feeding on fruit which enables rot organisms to enter fruit.
Rapid shoot growth
Early in rapid shoot growth, start monitoring for webbing on leaves caused by omnivorous leafroller, orange tortrix, or light brown apple moth to map out areas of concern for bloom monitoring. Unroll leaves with orange tortrix or light brown apple moth and look for leafroller larva, pupa, or parasite cocoons. Check for leaves skeletonized by western grapeleaf skeletonizer.
Plan to treat omnivorous leafroller, grape leaffolder, and western grapeleaf skeletonizer (also, orange tortrix or light brown apple moth in coastal regions), if they have been a problem in the past or if there is no evidence of parasitism. If they haven't been a problem in the past, or if parasitism is present, be sure to monitor flower clusters or leaves for the caterpillars and damage they cause in wine/raisin grapes or in table grapes, as described below, to determine the need for treatment.
Monitor during the growing season in wine/raisin grapes or in table grapes, by examining fruit clusters for omnivorous leafroller, orange tortrix, and light brown apple moth and leaves for grape leaffolder and western grape leaf skeletonizer, following the guidelines below. Treatment after veraison for omnivorous leafroller, orange tortrix, and light brown apple moth is limited in effectiveness and not recommended. However, veraison monitoring for all these caterpillars will alert you to larval damage going into harvest and potential problems the following year.
At harvest, check fruit clusters for damage by omnivorous leafroller, orange tortrix, and light brown apple moth to assess this year's management program, natural enemy populations, and to plan for next year. Also assess grape leaffolder damage in table grapes.
HOW TO MONITOR
PROCEDURE AND TREATMENT THRESHOLDS
UC IPM Pest Management Guidelines: Grape
L. G. Varela (Crop Team Leader), UC IPM Program, Sonoma County
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