Effects of gibberellic acid on fruit, 'hen and chicken' condition, and vine development in the following season of Waltham Cross grapes

Abstract

Three experiments were conducted to assess the effects of GA on Waltham Cross grapevines. In the first-at Coomealla-a bunch dipping experiment-larger berries were produced and bunch weight was increased from 426 g to 840 g by dipping in a 10 p.p.m. solution and to over 1000 g with 40 or 160 p.p.m. at full bloom. The percentage of seeded berries was reduced from 97 per cent to 29, 14, and 10 respectively by these treatments. Later treatments were less effective. The two other experiments-one at Griffith and one at Coomealla-involved spraying whole vines at 10 and 20 p.p.m. Effects were much less clear cut, bunch weight was sometimes reduced and at Griffith the 'hen and chicken' condition was accentuated. In the year following whole vine treatment, serious crop losses were recorded as a result of failure of buds to burst. Bunch number per vine was reduced from 52 to as few as 11.4 where 20 p.p.m. had been applied at the shatter stage. Abnormal shoot development was also apparent.