Zucchini yellow mosaic virus disease of cucurbits in a tropical environment: aphid vectors, alternate hosts, and epidemic drivers
Roger Jones: DPIRD
<div>Irrigated crops of pumpkin, melon and watermelon are grown in tropical northwest Australia where agriculture is <60 years old. They suffer severe epidemics of the Southeast Asian <em>Zucchini yellow mosaic virus</em> (ZYMV) strain which is absent elsewhere in Australia. Eleven surveys were undertaken in 2015-2017 to establish which aphid species occur, when aphids spread ZYMV during the growing season and where ZYMV and aphids survive outside the growing season. Growing season data collection blocks of watermelon gathered information on aphid numbers and ZYMV incidence. All-year-round aphid trapping used sticky traps. Samples were collected for virus testing (ELISA, RT-PCR) and aphid identification (light microscopy, PCR). Six aphid species were present, three of which transmitted ZYMV, <em>Aphis gossypii</em>, <em>A. craccivora</em>, and <em>A. nerii</em>. Outside the growing season, ZYMV was rarely detected and only in volunteer cucurbits, wild melon vines and home garden cucurbit plantings. The aphid vector reservoir was much larger: <em>A. gossypii</em> survived on home garden cucurbit crops, volunteer cucurbits, wild afghan melon, wild melon vines, milkweed (<em>Euphorbia hirta</em>), and native rosella (<em>lbemoschus ficulneus</em>); <em>A. craccivora</em> on legume crop plants in home gardens, <em>Sesbania</em> rootstocks in sandalwood plantations and legume weeds; and <em>Aphis nerii</em> on calotrope (<em>Calotropis procera</em>). Underlying environmental factors driving the annual ZYMV epidemics in this remote region will be described</div>
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