Cornell University’s Dr. Terence Robinson, based on years of apple thinning research, has developed practical suggestions for New York growers to guide them in targeting optimum fruit sizes.
For Gala apples, he has determined that optimum fruit size is around 113-count. That number is equivalent to 7 to 10.5 fruit per square centimeter of the trunk cross-sectional area, a number that was determined by normalizing years of thinning yield data and looking at the trunk diameter number instead of tons per acre.
"We can produce larger Galas of 80-count in New York, but when we do, we reduce yield so much that the crop value back to the grower is less than it would have been if we had targeted a more moderate fruit size," he said.
He acknowledges that his recommendation is not the message New York growers want to hear, especially those who are involved in packing and selling fruit. "But we have learned there is a huge financial cost to overthinning for the fruit grower and packers don’t always understand that."
Trying to grow 200-gram Galas in New York is too expensive for the grower, he said, explaining that the crop value declines rapidly when yield is reduced beyond the optimum level.
However, for processing apples, there is no financial incentive for large fruit size. Robinson advises growers to carry larger processing crops as long as they do not become biennial. For example, in one of Robinson’s trials, the optimum crop level for a fresh market Empire orchard was 680 bushels per acre; the optimum for a similar Empire orchard grown for processing was 1,080 bushels.