Oily-grey blotches are produced on shoot stems. Bunches Ash-grey growth appears on young berries and bunch stalks. Severe infection causes delayed maturity, retarded growth of berries and splitting of berries. Crop loss Serious crop loss occurs on unprotected susceptible varieties, especially in cooler areas. Bunches with as little as 5 per cent disease may be rejected by wineries because they cause off flavours in wine.
Table grapes are unmarketable if berries or bunch stalks are infected.
Greatest losses occur in crops which are infected early. Susceptible varieties Most varieties are susceptible to the disease. The most susceptible wine varieties include Cabernet Sauvignon, Chardonnay, Chenin Blanc, Muller Thurgau, Muscadelle, Riesling, Semillon and Verdelho. The most susceptible table grape varieties are Cardinal, Flame Seedless, Red Emperor and Red Globe. It is important that sprays are not missed during this period.