How to Manage Pests

UC Pest Management Guidelines


Grape Bud Beetle

Scientific name: Glyptoscelis squamulata

(Reviewed 7/15)

In this Guideline:


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.

Common name Amount per acre** R.E.I.‡ P.H.I.‡
(Example trade name)   (hours) (days)

Calculate impact of pesticide on air quality
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.

(Imidan 70W) 1.33 lb 336 (14 days) See label


COMMENTS: To protect honey bees, apply only during late evening, night, or early morning when bees are not present.
** Apply with enough water to provide complete coverage.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I. The longer of two intervals is the minimum time that must elapse before harvest.
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For more information, see the Web site at



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448

Insects and Mites

L. G. Varela, UC IPM Program and UC Cooperative Extension, Sonoma County
D. R. Haviland, UC IPM Program and UC Cooperative Extension, Kern County
W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
F. G. Zalom, Entomology, UC Davis
L. J. Bettiga, UC Cooperative Extension, Monterey County
R. J. Smith, UC Cooperative Extension, Sonoma County
K. M. Daane, Kearney Agricultural Research Center, Parlier

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

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