The above article is all about late season use of fungicide sprays and the pre-harvest interval or PHI timing of sprays and its effects on fermentation.
Here is my summary:
Fungicide | Pre-Harvest Interval (PHI) | Effect on Fermentation |
Oxidate | Day of harvest | No issues |
Biofungicide Serenade |
Day of harvest | No issues |
Sulfur | 5-6 weeks | H2S (hydrogen sulfide) or rotten egg smell |
Copper | Late season usage | Copper is toxic to yeast and even non-lethal doses of copper can cause stress on the yeast, potentially leading to incomplete fermentation and release of undesirable metabolites, all leading to wine aroma defects |
Captan | Late season usage | Can delay the start of alcoholic fermentation, captan-treated grapes retained a definite cloudiness after six months of storage |
Manzate | 66 days before harvest | Preventing chemical residue and degradation product left on fruit; not necessarily affecting fermentation |
Ridomil MZ | 66 days before harvest | Preventing chemical residue and degradation product left on fruit; not necessarily affecting fermentation |
potassium bicarbonate (Kaligreen, Armicarb, Milstop) |
Late season usage | Contains potassium so best to avoid a heavy application shortly before harvest |
Botryticides Elevate, Vangard and Scala | Late season usage | Safe for both alcoholic and malolactic fermentation |
strobilurins (i.e., Sovran, Abound) |
Late season usage | No effect on fermentation but late-season use of strobilurins is not recommended due to possible fungicide resistance issues |
sterol inhibitors (i.e., Elite, Rally) |
Late season usage | No effect on fermentation |
powdery mildew fungicide Quintec | Late season usage | No effect on fermentation |
JMS Stylet Oil | Good late-season spray to reduce powdery mildew and European red mite | Some evidence that late applications depress Brix (sugar) accumulation due to a temporary reduction in photosynthesis; other California studies show no effect on fermentation |
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