Mealybug Pests and an Emerging Viral Disease: Temporal and Spatial Studies of Leafroll Disease and Mealybug Vectors

Grapevine leafroll disease is a threat to vineyard health and sustainability worldwide. Mealybugs are the main vector of consequence. This project is providing critical information on the relationship between mealybug populations and incidence of leafroll disease in Napa County vineyards. In the first of a three-year project, we identified thirteen vineyard study sites in Napa County. We collected data on mealybug damage to the fruit and disease incidence at each site, just prior to harvest. We will continue to do this each year during the next two growing seasons. We will then analyze the data to correlate vector incidence to disease. We are also developing the use of pheromone-baited sticky traps as sampling tools. Growers have traditionally relied on field sampling to provide information on mealybug life cycle and density. Sticky traps have the potential to be more sensitive than field surveys for detecting small populations of grape mealybug. We have continuously deployed pheromone-baited sticky traps at the thirteen vineyard study sites in Napa County. We detected grape mealybug males at all field sites. We gathered preliminary information on male flight patterns from June to December, 2010. One peak in the male flight was detected near harvest, corresponding to published information on the grape mealybug life cycle.