Biological Control of Obscure Mealybug, Pseudococcus Viburni, in the North and Central Coast Regions

Obscure and longtailed mealybug pest status and the effectiveness of natural enemies were studied in five vineyards in the Central Coast regions (San Luis Obispo and Ventura Counties) and one vineyard in Napa County. In all of these vineyards, samples were taken to determine the seasonal abundance of mealybugs and their natural enemies in order to estimate levels of natural control. In three of these vineyards (two in San Luis Obispo County and one in Napa) plots were established to investigate the role of ants on mealybug and beneficial insect abundance. Results showed mealybug populations, when left unchecked, can build to damaging levels because there are few efficient natural enemies resident in vineyards. The most common natural enemies resident in the vineyards were predatory beetles. Results also showed that ants tending mealybugs are quite disruptive to biological control; however, predatory beetles were present on vines with and without ants. In plots where ants were excluded, mealybug densities dropped significantly throughout the season and regardless of the levels of parasite activity (see below).