Authors
C.
Cabaleiro
,
Plant Pathology, Departamento de Ingenieria Agroforestal y Producción Vegetal, Universidad de Santiago de Compostela, 27002 Lugo, Spain
; and
A.
Segura
,
Plant Physiology, Departamento de Biología Vegetal, Universidad de Santiago de Compostela, 15706 Santiago de Compostela, Spain
ABSTRACT
The spatial distributions of grape plants with symptoms of grapevine leafroll in nine vineyards in the Galician wine-growing region Rías Baixas (northwestern Spain) were analyzed. In five, significant aggregations of diseased plants and/or disease gradients toward one of the borders of the plots constituted indirect evidence of vector transmission by a nonflying vector. From 1991 to 1995, vines from two vineyards were tested for grapevine leafroll associated virus 3 (GLRaV-3) by enzyme-linked immunosorbent assay. In one of these vineyards, which had been virus-free when planted, GLRaV-3 was detected 3 years after planting. In the second, the incidence of GLRaV-3 increased from 33 to 83% between 1991 and 1995. The mealybug Planococcus citri was associated with the infected plants in this vineyard. GLRaV-3 was present in P. citri, and under controlled conditions this mealybug transmitted GLRaV-3 to five of five previously healthy grape plants.
