Abstract
Greenhouse and field studies indicated that between 30 and 40 per cent. of tubers from spotted-wilt-diseased potato plants transmit the disease. Tubers with characteristic distortion and terminal cracking due to early infection show a lower rate of transmission than normal-looking tubers from diseased plants. There is a discontinuous distribution of virus within infected tubers, some parts being free of virus. Second-generation diseased tubers show approximately the same rate of transmission as first-generation diseased tubers, but the incidence of terminal cracking is very low. A high proportion of plants emerging diseased from 'seed' are capable of surviving throughout the season to act as a source of infection. Vector studies made by mass collection and by tanglefoot trapping showed that Thrips tabaci Lind. is the main vector species in the Canberra region. The causes of epidemic outbreaks and measures that may be taken to combat them are discussed.
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