|Subject||Raisin Molds and Rots|
Raisin mold is associated with a wide range of primary and secondary fungal organisms normally found in the vineyard. They include species of Alternaria, Aspergillus, Botrytis, Chaetomium, Cladosporium, Helminthosporium, Hormiscium, Hormodendrum, Penicillium, Rhizopus, and Stemphylium. Yeasts and driedfruit beetle are also important secondary contaminants.
Cultural practices and time of harvest can decrease the risk of raisin molds and rots and rain damage. Powdery mildew infections and bunch rot can be minimized with fungicide treatments, insect control, bloom-thinning gibberillin treatment, and irrigation and canopy management practices. Placing trays on a firm, smooth, steep terrace reduces water retention on trays after a rain. Also, minimizing crushed or broken berries during harvest, keeping clusters with rot off trays, and spreading the clusters evenly in a single layer can also reduce damage.
Fungicide treatments have also successfully reduced mold infections. Studies show that such materials must be applied before a rain to be effective. Post-rain treatments have not been effective, largely because infections have already occurred by application time and much of the mold originates on the inaccessible bottom fruit on the tray. Only use registered materials according to label restrictions.
Christensen, L.P. 1992. Raisin Molds and Rots. Page 111-112 in: Grape Pest Management, 2nd edition. University of |