Epidemiology and incidence of beet curly top geminivirus in naturally infected weed hosts

The incidence of beet curly top geminivirus (BCTV) infection in weeds in the San Joaquin Valley of California was investigated from May 1993 through February 1995. BCTV, which was detected by dot blot hybridization, was found to be naturally infecting a wide range of plant hosts. Weeds from 14 different plant families, as well as a Variety of crops, were found to be infected with BCTV. Weeds naturally infected with BCTV were generally asymptomatic. Infection rates for frequently collected plant species ranged from 2 to 11%. All but two of the BCTV-infected plants were collected from the valley floor in Fresno County. Infected plants were detected in all collections except for the final sampling date. As determined by hybridization, the virus titer in crop plants such as sugar beets and tomatoes was considerably higher than in weed hosts. This work suggests that BCTV exists year round within the San Joaquin Valley of California and that crop plants play an important role in virus survival.