Tackling Downy mildew in Vineyards
Grapes
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La Nina weather patterns over the past few years have contributed to severe outbreaks of Downy mildew in vineyards across the North and South Islands. This disease can defoliate grapevines, damage fruit and cause off-flavours in wine.

Paul Hassan, Syngenta Technical Services Lead, says: “This coming season and in years to come, the risk of further infection is higher than normal due to the greater loading of mildew spores in vineyard soils. By utilising predictive weather forecasting tools and adding two effective Syngenta fungicides to their Downy mildew control programme, viticulturists can achieve good control of this disease.”

AMISTAR® fits into the spray programme as a single preventative application ahead of rainfall to protect new growth through systemic, translaminar and anti-sporulant activity. Only one application of AMISTAR® should be made per season from early to mid-flowering, after pre-flower protectant sprays have been applied.

“RIDOMIL® Gold MZ has more flexibility,” says Paul. “Interestingly, some believe that RIDOMIL® Gold MZ can only be used after a rain event as a curative product but in many countries, it is used preventatively and works very well. This is a useful property, especially in large vineyard situations when vast areas need to be sprayed over a few days prior to a predicted weather event.”

Where possible, apply RIDOMIL® Gold MZ before predicted warm and wet conditions. “However, if the spray round is interrupted by rain, it can be applied after the rain to complete the spray round. Make this application as soon as conditions allow, no later than five days after the rain starts and prior to any visual symptoms of Downy mildew appearing.”

RIDOMIL® Gold MZ contains two actives: Metalaxyl-M (also known as Mefenoxam) and Mancozeb. No more than two, non-consecutive applications should be made per season.

Paul reminds growers to observe the PHI of each product and label relative to any required nil residue or managed residue export spray programme and to consult the latest New Zealand Vineyard Spray Schedule for guidance.

For more information on Downy mildew disease control in grapes, click to view Grapes Technote.