Biology and Control of the Grape Bud Beetle, Glyptoscelis squamulata (Coleoptera: Chrysomelidae), in Southern California Table Grapes

Abstract

Glyptoscelis squamulata, often called the grape bud beetle (GBB), is indigenous to North America. During the 1920’s and into the late 1940’s this univoltine species was considered the major pest of fresh table grapes in the Coachella Valley of southern California. Adult beetles feed on emerging buds and eat the immature leaves and flower cluster primordia. The larval stages are spent in the soil feeding on roots. The beetle has reappeared recently as a major pest of grapes. Adult emergence from the soil was monitored in five Coachella Valley vineyards. Peak emergence occurs in the last three weeks of March. Early-budding varieties such as ‘Perlette,’ ‘Cardinal,’ and ‘Beauty Seedless’ may suffer less damage than the late-developing ‘Thompson Seedless.’ Adults are active at night, making detection difficult with a flashlight. We found that the beetles glow a bright silver blue under ultraviolet light; detection can be made in seconds. Feeding and oviposition studies were conducted. Phosmet, azinphosmethyl, and dimethoate were applied for control of adult beetles at 1.41, 1.41, and 2.25 kg (AI)/ha, respectively. They gave statistically similar results and caused significantly higher mortality than diazinon and carbaryl, which were both applied at 1.80 kg (AI)/ha.