Vine Pest Spreading In California
By HOWARD G. GOLDBERG
Published: June 21, 1989
An infestation of an apparently new strain of grape phylloxera, a plant louse that destroys prime vineyards, has widened in the principal grape-growing regions of California since it was detected there in 1983.
Agricultural specialists affiliated with the University of California at Davis said that the slowly spreading strain, called Type B, has expanded in the Napa Valley and in Sonoma County, and that growers were worried but not alarmed.
The specialists said the more prevalent strain of grape phylloxera, Type A, which has been present in parts of California for a century, has invaded Lake and Medocino Counties, which are young grape-growing districts.
Prof. Jeffrey Granett, the chairman of the entomology department at Davis, said both strains of the insect posed ''no threat to California's wine industry but are a threat to individual growers.'' He said Type B has attacked a rootstock called AXR-1, which has been popular in California since the 1950's and was thought to be resistant to phylloxera.
When the pest assaults the roots of a vinifera vine - the kind that produces the best wine grapes - the quantity and quality of grapes diminishes and the plant may die.
To combat the pest, vineyard managers have turned to newer, more resistant rootstocks.
A plague spread by winged phylloxera wiped out most of France's finest vineyards in the 1860's and 1870's.
Ed Webber, the University of California's Cooperative Extension farm adviser in Napa, said the worst outbreak there covered two acres, but he declined to identify the owners ''because they are cooperating with the university.'' Otherwise, he said, phylloxera was found in ''20 to 30 spots, most of which are very small - 20 to 30 vines each are affected.''
Rhonda Smith, the farm adviser in Sonoma, said Type B is presumed to be all over Sonoma, but has been found in fewer than 10 locations.
The infection rate is slowed by the fact that Types A and B are wingless; the two types are yellow, pinpoint-sized and biochemically identical. Type A, like B, reproduces on the AXR-1 rootstock but does not ruin it. Type B multiplies faster than A. In young grape-growing regions like Monterey County - where, because there was no history of phylloxera, vinifera vines have been planted on their own roots - Type A is the primary strain.