Wine Australia Wine Sector Pest & Disease Debrief Sessions

The wet 2010-11 season had been ‘coming’ for a long time. The law of averages through the history of Australian viticulture had been ‘predicting’ a major wet season for some years despite the advent of a series of drought years prior to season 2009-10. This long drought had interrupted the historical cycle that extended across south-eastern Australia of one very wet season every nine years. At least in the inland districts of Riverland/Sunraysia this had held true, except for the ‘miss’ in 2001-02, in the middle of the drought. Then, interestingly, just nine years later again, came 2010-11, the next in the series of seasons favouring high levels of the foliage diseases of grapes across south-eastern Australia.

In recent memory, the years with high disease pressure across south eastern Australia similar to 2010-11 were 1973-74 and 1974-75, 1983-84 and 1992-93. Prior to that, the wet seasons of 1917 (when downy first appeared in Australia), of 1931, 1954-55 and 1955-56 stand above the other seasons. So, in the 75-year period to 1992-93 since downy mildew was first observed in Australia, at least eight years – or one year in nine – were prominent from the amount of rain and the copious damage caused by the foliage diseases in vineyards.