Abstract
Elemental sulfur (S0) is commonly used to control powdery mildew in vineyards, but S0 residues in musts have been correlated with increased hydrogen sulfide (H2S) and sulfurous off-aroma formation during fermentation. As a consequence, S0 is often used sparingly late in the season, but defining appropriate preharvest intervals for S0 sprays has been challenging due to limited data on S0 persistence in vineyards and during prefermentation operations. Using a new quantification method, S0 residues were monitored in the vineyard over three years of field studies. Treatments varied in commercial formulation, application rate, and timing of the last application before harvest, all of which affected S0 concentrations on the fruit at harvest. Residue concentrations generally were lower for a wettable powder versus a micronized formulation applied at the same rate and timing and increased proportionally to the application rate when timing and formulation were constant. In all years, ceasing application ≥35 days prior to harvest resulted in S0 residues below the 10 μg/g concentration associated with increased H2S production in several previous studies. S0 residues >1 μg/g correlated with increased H2S production in our current work and were observed on all fruit sprayed within 56 days of harvest. However, clarification decreased S0 in must by >95% prior to fermentation in all treatments. Furthermore, fermentation on treated skins increased H2S formation nearly 3-fold over fermentations without skin contact. Collectively, these results indicate that S0 residues are likely of low concern in white winemaking, whereas residue concentrations in red fermentations can exceed those associated with increased H2S production when some S0 sprays are applied within eight weeks of harvest.
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Claims 10
Claim · model-written summary
Spray formulation, rate and timing affected sulfur concentrations on fruit at harvest.
- Taxon
- Grapest0
- Treatment
- commercial formulation, application rate, and timing of the last application before harveste0
- Outcome
- S0 concentrations on the fruit at harveste0
Not reportedDirection
Verbatim
t0“Grapes”
e0“Treatments varied in commercial formulation, application rate, and timing of the last application before harvest, all of which affected S0 concentrations on the fruit at harvest.”
Claim · model-written summary
Wettable powder left lower fruit sulfur residue than micronized formulation at the same rate and timing.
Verbatim
t0“Grapes”
e0“Residue concentrations generally were lower for a wettable powder versus a micronized formulation applied at the same rate and timing”
Claim · model-written summary
Fruit sulfur residue increased proportionally with application rate when timing and formulation were constant.
Verbatim
t0“Grapes”
e0“increased proportionally to the application rate when timing and formulation were constant.”
Claim · model-written summary
Stopping sulfur application at least 35 days before harvest produced residues below 10 μg/g in all years.
- Taxon
- Grapest0
- Treatment
- ceasing application ≥35 days prior to harveste0
- Outcome
- S0 residuese0
- Direction
- belowe0
- Value
- 10 μg/ge0
Not reportedComparator
Verbatim
t0“Grapes”
e0“In all years, ceasing application ≥35 days prior to harvest resulted in S0 residues below the 10 μg/g concentration”
Claim · model-written summary
Residues above 1 μg/g correlated with increased hydrogen sulfide production.
Verbatim
t0“Grapes”
e0“S0 residues >1 μg/g correlated with increased H2S production in our current work”
Claim · model-written summary
Fruit sprayed within 56 days of harvest had sulfur residues above 1 μg/g.
Verbatim
t0“Grapes”
e0“S0 residues >1 μg/g correlated with increased H2S production in our current work and were observed on all fruit sprayed within 56 days of harvest.”
Claim · model-written summary
Clarification reduced sulfur in must by more than 95% before fermentation across all treatments.
Not reportedComparator
Verbatim
t0“Grapes”
e0“clarification decreased S0 in must by >95% prior to fermentation in all treatments.”
Claim · model-written summary
Fermentation on treated skins increased hydrogen sulfide formation nearly threefold over fermentations without skin contact.
Verbatim
t0“Grapes”
e0“fermentation on treated skins increased H2S formation nearly 3-fold over fermentations without skin contact.”
Claim · model-written summary
The authors conclude sulfur residues are likely of low concern in white winemaking.
Verbatim
t0“Grapes”
e0“S0 residues are likely of low concern in white winemaking”
Claim · model-written summary
The authors conclude red fermentations may exceed residue levels linked to increased hydrogen sulfide after sprays within eight weeks of harvest.
Verbatim
t0“Grapes”
e0“residue concentrations in red fermentations can exceed those associated with increased H2S production when some S0 sprays are applied within eight weeks of harvest.”
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