How to Manage Pests
UC Pest Management Guidelines
Grape Bud Beetle
Scientific name: Glyptoscelis squamulata
In this Guideline:
DESCRIPTION OF THE PEST
The grape bud beetle is a major pest in the Coachella Valley. It can be found in the Central Valley but is rarely if ever a pest problem there. The adults are a light gray color. Both sexes are about 0.25 to 0.4 inch (6–10 mm) long and 0.2 to 0.25 inch (5–6 mm) wide. There is one generation per year and larval stages are spent in the soil. Adults begin emerging from the soil in mid-January; peak emergence occurs around mid-March each year. Emergence time is not affected by aboveground temperatures.
Adult beetles cause crop loss by feeding on opening buds and eating the bud center, which contains the immature leaves and flower cluster primordia. Once the new shoots are 1 to 1.5 inches long, feeding damage is negligible.
An important part of managing grape bud beetle is keeping accurate yearly records of infested vineyards. These beetles usually occur in localized areas of a vineyard year after year. Because grape bud beetles are not equally distributed, survey all parts of a vineyard.
Monitoring and Treatment Decisions
Adults come out of daytime hiding places about 1 hour after sundown. Beetles can be monitored with a flashlight. An ultra-violet lamp is preferred because the beetles naturally fluoresce a bright silvery blue when under UV light.
Treatment decisions for adults are complex. For example, unusually warm weather can push the buds out rapidly, or cold weather may delay budbreak and provide longer exposure of buds to beetle feeding. A variable portion of buds of all varieties never open in the Coachella Valley.
During budbreak, treatment is suggested when there are one to three beetles per vine and bud damage is noticeable in Thompson Seedless vineyards. Treatment is suggested during budbreak in Beauty Seedless, Perlette, Flame Seedless, and Cardinal vineyards when there are one to two beetles per vine and bud damage is noticeable.
UC IPM Pest Management Guidelines: Grape
Insects and Mites
L. G. Varela, UC IPM Program and UC Cooperative Extension, Sonoma County
Acknowledgment for contributions to Insects and Mites:M. C. Battany, UC Cooperative Extension, San Luis Obispo County
J. Granett, Entomology, UC Davis
P. A. Phillips, UC IPM Program, Ventura County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley