Homalodisca coagulata can transmit citrus variegated chlorosis
Citrus variegated chlorosis is caused by a strain of Xylella fastidiosa (EPPO A1 list) which is transmitted by several species of xylem-feeding insects. Homalodisca coagulata (Homoptera: Cicadellidae – EPPO Alert List) has become an important pest of citrus and grapevine in California (US). It has been shown that it can transmit X. fastidiosa strains to several crops including grapevine (causing Pierce’s disease), oleander (oleander leaf scorch) and almond (almond leaf scorch). In California, the establishment of H. coagulata has led to an increase of grapevine Pierce’s disease. So far, citrus variegated chlorosis has not been reported outside Argentina, Brazil and Costa Rica and it is not known whether H. coagulata can transmit this disease. Transmission studies were done in quarantine facilities in Maryland (US) using H. coagulata collected from California, a Brazilian strain of citrus variegated chlorosis and sweet orange seedlings as test plants (Citrus sinensis cv. Madam Vinous). The presence of X. fastidiosa in the test plants was detected on the basis of visual symptoms, PCR with specific primers, membrane entrapment immunofluorescence and electron microscopy. Results showed that H. coagulata could transmit citrus variegated chlorosis but with a low level of transmission. It is concluded that citrus variegated chlorosis represents a serious threat to citrus-growing areas of North America where H. coagulata is now established such as Florida, Texas and California.
Sources
Damsteegt VD, Brlansky RH, Phillips PA, Roy A (2006) Transmission of Xylella fastidiosa, causal agent of citrus variegated chlorosis by the glassy-winged sharpshooter, Homalodisca coagulata. Plant Disease 90(5), 567-570.