Developing a downy mildew management decision webpage for Western Australian wine regions

Abstract

This study was aimed at determining the current understanding of downy mildew of grapevines in WA vineyards.

Summary

Downy mildew first appeared in WA ten years ago and is now established in the majority of growing regions with management being required by growers to prevent severe yield loss. Localised outbreaks of the disease are quite common in WA but the 2008/09 saw significant infection events occur across many of the growing regions.

Peter Magarey, Magarey Plant Pathology South Australia, visited WA and presented current information to groups in the Margaret River and Frankland River regions during 2009. These regions were selected as Margaret River has experienced downy mildew at a localised level for several seasons whereas 2008/09 was the first record of downy mildew in Frankland River. Peter presented information regarding lifecycle, symptoms and signs of disease, pre infection and post infection management and other control options.

At each of these workshops a questionnaire was handed to participants to gauge current grower understanding on downy mildew. Sixty-two growers from both workshops answered questions regarding spray programs, disease severity, disease monitoring, management techniques and weather monitoring. Results from the questionnaire revealed the majority of growers in WA manage downy mildew through a preventative spray program and that this program is successful in most years in controlling downy mildew. As expected differences were found between the two regions in the study in terms of bag testing for downy mildew and alternate plans when post infection spray options are exhausted.