Investigation of Defects in Grapes Delivered to California Wineries: 1958

¹ Department of Viticulture and Enology University of California, Davis

Delay in harvesting causes increased rot, as do overcropping and late irrigation. Wine grapes are generally more susceptible to rot than table and raisin grapes. Area per se has no effect. Rain during the vintage greatly increases rot.

The degree of insect infestation varies between areas and seasons, and with time of harvest. Varietal differences in susceptibility to infestation are due mainly to differences in cluster compactness. Infestation increases with increasing amounts of rot up to a maximum, but rot can be used only in a general way as an index of the degree of infestation. The data obtained to date are insufficient fo establish industry-wide grades for defects for all grape varieties.

Three 42-pound samples from a gondola load are representative of the bunches in the load. The mean of single samples taken af the E position from two or more loads is representative of the true mean of the bunches in the loads. Three 82-pound samples from a gondola load are not representative of the berries in the load.