ROT MANAGEMENT IN REDS
ROT MANAGEMENT STRATEGYRot management is a part of your integrated pest management (IPM) strategy. However, despite your best control strategies you may still have to harvest fruit compromised by Botrytis cinerea or other microorganisms. Botrytis grows intracellularly and infects fruit primarily under the grape skin, secreting a damaging and stable enzyme called laccase. In extreme cases Botrytis can cause “slip skin”, making the fruit very difficult to handle.
When Botrytis or other rots are present on red grapes, the resulting wine quality can be negatively impacted. Depending on the mold and bacteria present, there are serious enological concerns, such as oxidative browning, degradation of color and aromatic compounds, as well as clarification and possibly filtration challenges.
The first step in dealing with compromised fruit is to evaluate the mold level (both on the cluster, within the cluster and inside the berries) and to sort the grapes, separating the fruit so that you are dealing with the cleanest fruit available. Afterward, don’t forget to clean your picking bins as well as your winery equipment to minimize cross-contamination.
TIPS FOR DEALING WITH INFECTED GRAPESAnalysis is key!
Pre-fermentation analysis (chemical and microbiological) allows you to make good winemaking decisions.
Post-fermentation analysis allows you to move forward while determining risk.
Must is very sensitive to damage from laccase.
Increase your initial SO2 addition, and consider using Lysozyme if secondary lactic infections are evident.
Minimize time between picking and inoculation (no- cold soak).
Choose a yeast with a short lag phase, low VA production and good mouthfeel. Increase your yeast dose to insure a fast start to fermentation.
If a late Sulfur spray was done in the vineyard, you may wish to consider using a non-SO2 / H2S producing wine strain.
Consider co-inoculation with ML to get your wine protected earlier.
Keep free run and press fractions separate until you have determined risk.
Separate heavy fermentation lees ASAP, as the lees contain most of the laccase.
Keep tanks/barrels topped and treated.
Minimize oxygen exposure, consider the use of gas, dry ice or a sparging stone.
Do not blend laccase positive and laccase negative wines.
If heat treatment is available, that is a very good tool to deactivate the laccase.