Optimizing Fungicide Use and Timing Based on Weather Conditions

Research Date
Annemiek Schilder, Jeffrey Andresen, Christine Vandervoort
Best Practices, Crop Quality, Disease Management, Pest Management
Crop Categories
Beverage Categories

A study on environmental effects on fungicides applied to grape leaves showed that moderate temperatures were optimal for fungicide uptake and retention and that Abound (azoxystrobin) became undetectable when applied at 40 degrees F. Efficacy of Abound, Manzate (mancozeb) and Phostrol (phosphorous acid) against Phomopsis cane and leaf spot was optimal when applied as preventative sprays a week or less before infection. Fungicides sprayed on grape clusters in full bloom reduced cluster weight and number of berries at harvest, suggesting that they interfere with fertilization. Further research is needed but it seems advisable to avoid fungicide sprays at full bloom.

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