Scarring of Thompson Seedless table grapes

The studies reported here show that some table Thompson Seedless grapes grown in the southern San Joaquin Valley are subject to a scarring problem and this scarring may occur to some degree even when no sprays are applied to the berries. When sprays are applied during bloom and after, the degree and severity of scarring tends to increase. That scarring could be found on berries when the calyptras persisted after bloom, suggests that they play some role in the scarring injury. While the scarring is similar in its superficial nature to that caused by thrips, the pattern is different. Since thrips were not eliminated from the tests, studies during 1972 will attempt to evaluate the relationship between adhering calyptras, spray timing and thrips feeding.