|Chardonnay at 9o Baume ripeness.|
High risk varieties have tight bunches and thin berry skins. It is also possible to see botrytis in 'green fruit' which hasn't ripened yet.
High = Sav. Blanc, Riesling, Grenache, Semillon, Chenin Blanc
Medium = Viognier, Pinot Gris, Pinot Noir, Chardonnay, big bunched Shiraz,
Sangiovese, Mataro/Mouvedre, Petit Verdot, Verdelho
Low = Small bunched Shiraz, Merlot
Very Low = Cabernet Sauvignon
There are exceptions to these rules- different vineyard sites, croploads, canopy management and chemical strategy have an effect on the amount of rain a block can receive before showing signs of disease.
If heavy rain occurs and your grapes are riper than 9o Baume look inside the canopy for any evidence, especially in thin-skinned and tight bunched varieties. Semillon, Sauvignon Blanc, Chenin Blanc, Grenache, Chardonnay & Viognier are the first varieties that will show problems.
Botrytis needs significant rain or heavy dews to spread. If the weather remains fine any botrytis infections will hold to harvest and not significantly affect wine.
Be alert for rain in the next few weeks and assess your vineyard for any moulds. ALWAYS consult your grower liaison officer or winemaker before spraying for botrytis.