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How to Manage Pests

UC Pest Management Guidelines

Grape bud beetle, Glyptoscelis squamulata, female and eggs on bark.


Grape Bud Beetle

Scientific name: Glyptoscelis squamulata

(Reviewed 6/06, updated 6/06)

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 bud break 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/Acre** P.H.I.+
(trade name)   (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
A. DIMETHOATE 25WP 6–8 lb 28
  MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
  COMMENTS: Restricted entry interval: 2 days. Moderately disruptive to beneficials.
  (Imidan) 70WP 1.33 lb 7
  MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
  COMMENTS: Restricted entry interval: 5 days
**  Apply with enough water to provide complete coverage.
+ Preharvest interval. Do not apply within this many days of harvest.
1 Modes of action are important in preventing the development of resistance to pesticides. 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. 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 is assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
F. G. Zalom, Entomology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
P. A. Phillips, UC IPM Program, Ventura County
D. R. Haviland, UC IPM Program, Kern County
K. M. Daane, Kearney Agricultural Research Center, Parlier
M. C. Battany, UC Cooperative Extension, San Luis Obispo County
Acknowledgment for contributions to Insects and Mites:
J. Granett, Entomology, UC Davis

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