Speaking at the International Workshop on Grapevine Trunk Diseases in Adelaide, he explained, ‘This is because trunk diseases are more widespread than phylloxera, and there is presently no control for trunk diseases, but there is for phylloxera.’ He is concerned that official Australian wine policy and measures are more concerned with phylloxera and grapevine virus diseases than with the fatal vine trunk diseases which have become such a problem in vineyards in recent years.
Recent surveys in Australia and New Zealand have shown that older vines are more prone to the disease than young ones, but that is a relative term with some vines as young as 10 years affected by vine trunk diseases. According to Dr Smart’s calculations concerning vine plantings since 1988, average vine age is 14 years in Australia and eight years for New Zealand, ‘and so the next decade will see even more trunk disease damage, especially for Australia', he claims.
While New Zealand vines are generally younger than Australian ones, French and Australian studies have shown Sauvignon Blanc, New Zealand’s dominant grape variety by far, to be one of the most susceptible to trunk disease.
Smart also commented on the status of newly grafted vines he sees in his travels worldwide. ‘They are uniformly showing symptoms of trunk diseases', he claimed. ‘They can grow well when properly tended, but they appear more sensitive to stress, and are potential sources of infection for the future. This is a widespread problem. Nurseries all over the world, in Europe, the US, Australia and New Zealand are all producing vines with trunk disease symptoms.’
Dr Smart said that he had no doubt that methods would be developed to overcome trunk diseases – probably in the next ten years. Barossa Valley growers are already developing methods of overcoming trunk disease infections. But he predicts that the solution will be considerably more complex than grafting on to phylloxera-resistant American rootstocks eventually proved as a counter to the predations of phylloxera in the late nineteenth century.
