Drop Of White The Right Stuff For Vines

Peter Crisp from the University's Department of Applied and Molecular Ecology is examining novel control methods for powdery mildew for his PhD, and has already attracted interest from the wine industry with his preliminary findings. Powdery mildew is a disease which attacks grapevine leaves and fruit, and currently costs the Australian wine industry about $30 million a year, mainly in control measures.

"A lot of people are already using milk on their household potplants to make the leaves shiny - but now its benefits are being formally recognised," Mr Crisp says. "For the first part of my study, I examined 30 or 40 different treatments, some of them "snake oils" or "old wives' tales", that are in circulation for treating powdery mildew. Unsurprisingly, most of them did not provide good control, but milk and whey, and also a canola oil-based product, stood out as being comparable to current powdery mildew treatments."

The most successful treatments Mr Crisp has trialled so far are milk and whey (the liquid waste from cheese production). The milk is diluted to 1/10th of its normal strength, and the whey 1/3rd, and the solutions sprayed onto the grapevine leaves and immature grapes. The solutions work well on most grape cultivars and, importantly, don't appear to affect the quality of the grapes and hence the finished wine product, although this needs to be evaluated experimentally. The success of milk as a control of powdery mildew on grapevines supports earlier research on zucchini in Brazil.

"Making sure that the quality is not diminished is very important for the commercial wineries - obviously they don't want to put anything on their grapes which will reduce the quality of their wines, and subsequently reduce the price and reputation the wines can achieve," Mr Crisp says.

The implications of Mr Crisp's research are biggest for organic winemakers, those who don't currently use synthetic fungicides and herbicides for disease and pest control.

"Sulphur is the main form of fungicide used against powdery mildew, and is used in most organic and conventional wineries, with the conventional vineyards using synthetic fungicides as well. Sulphur has been used for 150 years and is pretty effective, but it may in the future be restricted for organic growers to use, and they'll need to find another way which will be cheap and efficient," Mr Crisp says.

Several organic wineries are already involved with Mr Crisp's research, notably Temple Bruer in Langhorne Creek. Temple Bruer Wines CEO David Bruer was former Head of the Oenology Department at the University's Roseworthy campus before becoming a full-time vigneron and has generously allowed Mr Crisp to use a portion of his vineyard for trials. Other wineries involved in Mr Crisp's project include Glenara and Mountadam.