Botrytis is one of the wine industry's most damaging diseases and controlling it is a billion dollar challenge for the business. But scientists in New Zealand claim to have discovered a biological control. Frank Smith reports on the potentially ground-breaking discovery.

A group of New Zealand scientists have discovered a biological control agent for botrytis, one of the international grape growing industry's main diseases. And the leader of the team, Dr Phillip Elmer of NZ research organisation HortResearch, describes the discovery as a true breakthrough.

"Bunch rot is a major problem for the wine industry and the disease, also known as grey mould, is arguably the single most important disease problem confronting the international wine industry," he says.

Bunch rot is caused by the fungus Botrytis cinerea, which also attacks other berry fruit crops and in certain circumstances can cause noble rot, a non-destructive condition which produces botrytised wines.

"With mechanical harvesting predominant in the industry, infected grapes cannot be separated from healthy ones at the time of harvest," Dr Elmer explains.

"The product is completely organic, and it controls the botrytis without affecting the grape"
Dr Phillip Elmer

The disease leads to a reduction in wine quality as well as loss of yield. To prevent this, crops must be sprayed with fungicide several times during grape development.

"One of the real attractions of the product is that it is completely organic, rather than chemical based, and it controls the botrytis without affecting the grape," he continues.

Winegrowers everywhere recognise the importance of reducing the industry's reliance on synthetic fungicides, but particularly in New World countries which use their 'clean green' image as a marketing tool.

Plant Pathologist Peter Wood said botrytis bunch rot can be a serious problem in Australian vineyards. "Rain in the warmer months is dynamite for botrytis," he said. "This development looks quite exciting. If it works as well or better than fungicide that would be terrific."

Botryis bunch rot of grapes

Zenith Technology Corporation Ltd of Dunedin in New Zealand has developed a formulation and manufacturing process, and the new product should be in production within a year.

Dr Max Shepherd, executive director of Zenith, is confident that Botry-zen will be competitive with conventional fungicides including the newer products. "At the moment we expect the cost of each spray to come to about $NZ120/spray/hecatare.

"Three treatments are required; at flowering, bunch formation and veraison," he said.

The biocontrol organism is a naturally occurring fungus, which lives entirely off dead and dying plant material. It is widespread in soils but Dr Shepherd declined to name it at this stage.

The fungus works by competing aggressively with botrytis for physical space on the plant surface and by out-competing germinating botrytis spores for nutrients on the vine and grape surface. Without these nutrients the botrytis organism cannot grow and increase in numbers sufficiently to invade living plant tissue.

The biocontrol agent, to be marketed as Botry-zen, has not yet been registered for use on vineyards. "We submitted registration data to the New Zealand Pesticides Board two months ago and have already had a preliminary report back," said Dr Shepherd.

Marlborough Vineyard

"We have trials planned in the three main grape growing areas of New Zealand - Gisborne, Hawkes Bay, and Marlborough"

Dr Max Shepherd

"I am optimistic that Botry-zen will be available for the 2001/2002 season in New Zealand, however we have trials planned in the three main grape growing areas of New Zealand - Gisborne, Hawkes Bay, and Marlborough - in case the Board requires further work.

"We are also trialing the product in berry fruit crops, particularly blackcurrant."

International aspirations "We are looking for international partners to manufacture and sell Botry-zen under license," Dr Shepherd says. Protecting the intellectual property of a biological control agent is not always easy and has sometimes delayed the application of biological control applications.

But Shepherd explains: "Our patent covers the organism itself, which has never been used for this purpose before. We are also seeking to protect proprietary information about the manufacturing process."

The discovery was made by a team of scientists from HortResearch, the New Zealand research organisation spun off from the former horticultural division of Department of Scientific and Industrial Research.

The research was jointly funded by HortResearch, the Wine Institute of New Zealand and the New Zealand Grapegrowers Council, through their joint research arm, Winegrowers of New Zealand.