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Solarization of winery waste can prevent spread of vine mealybug

The Issue

Vine mealybug is an introduced pest in California that causes feeding damage and is capable of transmitting grapevine viral diseases that significantly reduce fruit and wine quality. The insect is very small and often goes unnoticed until populations rise and sticky honeydew accumulates on leaves, trunks and grape clusters. The insect can be spread to uninfested vineyards on farm equipment and workers' clothing. To prevent such spread, growers wash equipment before entering uninfested vineyards and hand crews wear disposable coveralls in infested vineyards. Using unfermented pomace as fertilizer in vineyards was thought to be another route for mealybug movement. Pomace is berry skins, seeds and cluster stems left over from the wine making process.

What Has ANR Done?

In trials at two wineries, UC Cooperative Extension researchers verified the survival of vine mealybug in unfermented pomace. Infested clusters were added to grapes processed in a grape press. Insects survived the press at each winery. This research demonstrated that growers and wineries can prevent vineyard contamination with mealybugs by not spreading pomace in vineyards or stockpiling it near vine rows. Management of this waste was still an issue for the industry. Unfermented winery waste is not commonly composted, and it may remain in static piles for weeks or months. UC advisors compared the fate of vine mealybug in pomace piles covered with clear plastic with their fate in uncovered piles. Results showed that covering pomace for one week reduced the number of live vine mealybugs by nearly 100 percent.

The Payoff

Solarization with clear plastic kills vine mealybugs in pomace piles

The researchers have delivered this message in presentations in winegrape growing regions across the state. They also published the research results in California Agriculture journal (Vol 62, No. 4). Spreading fresh pomace in north coast vineyards is no longer a standard practice. Nearly all unfermented pomace piles are covered for at least a short period of time or are in locations that are not adjacent to grapevines. A larger number of wineries are turning the piles to speed the decomposition of skins and stems. One estate winery in Sonoma County now composts pomace from 3,500 tons of grapes it processes each year.


Supporting Unit: Integrated Pest Management

Rhonda J. Smith, (707)565-2621, rhsmith@ucdavis.edu

Lucia G. Varela, 707) 565-2621, lgvarela@ucdavis.edu