Forecasting green-bridge mediated diseases in the south-west of Australia: Bean yellow mosaic virus in lupins.

Bean yellow mosaic virus (BYMV) is a non– persistently aphid–borne virus which causes significant yield losses in lupin crops. Strains that occur in the Mediterranean–type environment of south–west Australia are seed–borne in clovers and its principle reservoir is infected annual clover pastures in which it survives over summer within dormant seeds. Spread to lupin crops occurs when a BYMV–infected pasture is adjacent to the lupin crop and aphid vectors transfer the infection. The BYMV–lupin pathosystem is driven by the magnitude of the ‘green–bridge’ which depends on the amount of soil moisture before lupins are sown. Aphids build up in the ‘green–bridge’ and the longer this occurs before lupins are sown, the larger the BYMV epidemic in the pasture and the higher the likelihood that aphids will transfer BYMV from the pasture to the lupin crop early, generating a substantial epidemic. The BYMV–lupin pathosystem model requires daily temperature, rainfall and evaporation data to function, which it accesses from an associated meteorological database. The framework we have developed automates BYMV risk forecasting for over 450 sites, allowing for higher resolution, more frequently updated forecasts than previously possible. These forecasts were validated with data collected over two years from four geographically isolated trial sites.