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.
Bloom
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.
After Bloom
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.
Harvest
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
- Monitor 20 vines weekly by looking at 5 vines in each quadrant of the vineyard.
- On each vine, check for pests and the damage they cause by following the guidelines below.
- Record results on a monitoring form (example form—PDF) and treat using the treatment thresholds below.
Procedure And Treatment Thresholds
| Caterpillar | Procedure | Treatment threshold |
|---|---|---|
| Omnivorous leafroller |
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| Orange tortrix (Coastal regions only) |
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| Grape leaffolder |
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| Light brown apple moth |
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| Western grapeleaf skeletonizer |
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