OCCURRENCE AND DISTRIBUTION OF CUCURBIT VIRUSES IN THE HAWAIIAN-ISLANDS

Zucchini yellow mosaic virus (ZYMV), an isolate of papaya ringspot virus infecting watermelon (PRSV-W), and cucumber mosaic virus (CMV) were found infecting commercially grown cucurbits on the Hawaiian islands of Oahu, Maui, and Molokai during 1988 and 1989. Although previously reported in the Hawaiian Islands, watermelon mosaic virus 2 (WMV-2) was not found. Composition of virus epidemics varied widely among the three islands, even though all three viruses, alternate weed hosts, and aphid vectors are present throughout the state. Twenty-eight weed species were sampled. CMV, PRSV-W, and ZYMV infections were found in three species of the family Cucurbitaceae: Mormordica charantia (weedy form of bittermelon), Cucumis dipsaceus (wild cucumber), and Lagenaria siceraria (bottle gourd). Although many of the weed species tested did not appear to serve as alternative virus hosts, aphid surveys demonstrated that many of the same weed species are alternate hosts for at least five important aphid vector species, including Aphis gossypii and Myzus persicae. This information has implications for control of CMV, PRSV-W, and ZYMV in commercially grown cucurbits.