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Spring Aphid Flights and Incidence of Watermelon Mosaic Viruses 1 and 2 in Florida. W. C. Adlerz, University of Florida IFAS, Agricultural Research Center, Leesburg 32748; Phytopathology 64:350-353. Accepted for publication 14 September 1973. DOI: 10.1094/Phyto-64-350.

The peak of spring aphid flights in both central and south Florida usually occurred between the last week in March and the last week in April in the years 1966-71. Initial symptoms of watermelon mosaic virus 1 (WMV-1) were observed on watermelon in south Florida prior to the peak in spring aphid flights, whereas initial symptoms of watermelon mosaic virus 2 (WMV-2) in central Florida were observed after peak flights. This may explain why outbreaks of mosaic in south Florida are consistently more severe than those in central Florida. The difference in time of initial infection with the two viruses relative to peak aphid flights did not correlate with initial flights or abundance of specific vectors but may be explained by the distribution and abundance of weed hosts of the virus. In south Florida, the cucurbit weed Melothria pendula hosts a large reservoir of WMV-1 close to watermelon plantings. In central Florida, the principal source of WMV-2 remains to be identified, but the virus may occur in a variety of noncucurbit hosts. Reservoirs are probably small, necessitating relatively large numbers of aphids to effect initial transmission of the virus to watermelon. Myzus persicae was invariably present as a major component of the vector populations during initial and secondary spread of both viruses, and it is considered one of the important vector species.

Additional keywords: Aphis spiraecola, Aphis craccivora, Hyadaphis pseudobrassicae, epidemiology.