Leafroll is caused by a complex of viruses (grape leafroll associated viruses, GLRaV). Leafroll is a major disease of grapes worldwide. Virus infection leads to reduced vine vigor, reduction in sugar accumulation, negative impacts on the organoleptic  and keeping properties of wine and shortened vine lifespan.  In California the major virus type associated with leafroll is GLRaV-3, which is known to be vectored by several species of mealybug.  Four mealybug species are common in California vineyards: the grape mealybug, Pseudococcus maritimus, the obscure mealybug, Pseudococcus viburni, the long-tailed mealybug, Pseudococcus longi-spinus, and the citrus mealybug Planococcus citri.  A fifth mealybug species, the vine mealybug Planococcus ficus, has also been found recently in California and may be of concern as a new vector for GLRaV because of its potential for rapid population increase.




QBE lab’s role in leafroll research is focused on two issues. First, we are developing a sampling toolkit for the industry, based on statistical parameters of disease spread which can be collected on vineyards, to help growers make decisions about individual disease management plans.  Secondly, we are working with grower groups to develop local, collective action approaches to disease management.  This second element to our research and outreach may be crucial to sustainable disease management because of the potential for the disease to cross-infect vineyards.  The research involves collaboration with the Center for Environmental Policy and Behavior at UC Davis.




Work on leafroll epidemiology at the University of California is a team effort involving researchers from UC Davis, UC Berkeley and UC Riverside and UC Cooperative Extension specialists.


UCDavis:  Neil McRobertsKari ArnoldDeborah GolinoMark Lubell

UC Berkeley: Kent DaaneRodrigo Almeida

UC Riverside:  Matt Daugherty

UCCE: Monica Cooper