UC Delivers

Hot water can prevent spread of vine mealybug by grape nurseries

The Issue

Vine mealybug is a serious pest of wine, raisin and table grapes in California. Mealybug feeding reduces grapevine vitality, transmits grape viruses, and produces tremendous amounts of sticky honeydew, promoting sooty mold that renders the grapes unmarketable.

Until 2002, there was only one localized infestation of vine mealybug recognized outside of Riverside, Kern and Fresno counties. By the end of 2003, infestations had been documented in 16 counties, representing all grape-growing regions of the state. Subsequent investigations identified infested nursery stock as the cause for the rapid, widespread dissemination of this new exotic pest.

What Has ANR Done?

UC Statewide Integrated Pest Management entomologists David Haviland and Walter Bentley worked closely with the grape nursery industry to attack the problem at its source. They performed a series of hot-water treatment experiments on dormant grape cuttings and evaluated a wide range of immersion times and water temperatures for their effects on mealybug mortality. The results led to the development of a treatment program that was more than 99 percent effective at killing mealybugs on dormant nursery stock. Less than one mealybug per every 1,000 survived a five-minute treatment at 127 degrees F.

The Payoff

Research ends vine mealybug spread by nurseries

California grape nurseries that produce more than 90 percent of the grape nursery stock sold statewide have now adopted hot-water treatment programs to ensure that their nursery products are free of vine mealybug. Since these protocols have been in place, spread of vine mealybug through nursery stock has been eliminated.

Hot-water treatment programs continue to protect new vineyards from becoming infested, allowing them to get a healthy start toward contributing to California's $3 billion grape industry.

Contact

Supporting Unit: Kern County

David Haviland, (661) 868-6215, dhaviland@ucdavis.edu