RESPONSE OF RABBITEYE BLUEBERRY (VACCINIUM ASHEI READE) TO GIBBERELLIC ACID RATE

Recent observations and research in Georgia has revealed that substantial enhancement of rabbiteye blueberry fruit set and yield can be achieved on a commercial basis with properly timed applications of gibberellic acid (GA₃). Using GA₃ can be costly; hence, this research was conducted to determine the rate required for the growth regulator to be used effectively by growers. A greenhouse study evaluated GA₃ concentrations of 0, 84, 168, and 251 mg/liter applied to potted plants in excess spray volume until drip occurred. An observation in the field in 1994 examined rates of 0, 24, 47, and 94 g GA₃/ha applied with an air-blast sprayer to mature bushes in a spray volume of 375 liters/ha. In 1995, field rates were 0, 38, 56, and 75 g GA₃/ha applied in a similar spray volume. All applications were made to 'Tifblue' plants at bloom stages 5 to 6. Analysis of fruit set and yield data revealed there was a definite rate response to the growth regulator. We concluded that two applications at a concentration of 150 to 200 mg GA₃/liter gave a maximum response of fruit set. This translates into a field application rate of 50 to 70 g GA₃/ha applied in 375 liters/ha of spray volume. A collateral wash-off experiment indicated rapid uptake of GA₃ the first few hours following application, with residual uptake possible for 2 to 3 days after application.