Bemisia tabaci association with silverleaf of Cucurbita pepo
Silverleaf squash Cucurbita pepo has been several times associated with the presence of Bemisia tabaci (EPPO A2 quarantine pest). The causal agent of this disease, however, had not been conclusively determined. Studies carried out in Florida, US, revealed that an uncapsidated viral-like double stranded RNA (dsRNA) was consistently detected in plants showing silverleaf and in B. tabaci adults capable of mediating the disease. As reported at the 6th International Congress of Plant Pathology in Montreal, dsRNA quantities in B. tabaci adults are only limited and, therefore, the whitefly density is positively correlated with silverleaf rating. An average of 15-20 whiteflies per plant is necessary to induce the disease. Transmission experiments revealed the obligate requirement of whitefly for continued silverleaf development and the detection of dsRNA in the leaf tissues.
Sources
Bharathan, N. (1993) Uncapsidated viral-like double stranded RNA in whitefly-mediated silverleaf squash.
Presentation at the 6th International Congress of Plant Pathology, Montreal, CA, 1993-07/08-27/06.