Good Fruit Grower

May 15

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Optimizing Production Achieving the OPTIMAL CROP LOAD Precision pruning takes away much of the burden of thinning later. by Richard Lehnert T photo by geraldine warner he world doesn't need little, green apples, and growers need to stop making them. There has always been a penalty for small apples with poor color, and in some years, it's worse than others. Last year, processors needed apples, and they paid good prices for apples that wouldn't make it on the fresh market. But in most years, processing apple prices are not strong and importers stand ready to saturate conPrecision pruning is a good first step to adjusting crop load and producing fruit of the sumers with apple juice concentrate from best size and quality. Pruning to a specified number of buds starts the fruit thinning China and Poland. process at the earliest possible stage. In the long run, it is not clear how the apple industry will come to balance. Consumers eat about 60 percent of their apples in processed form, etting the optimal crop load starts with precision pruning and moves to the next step, precision so surely, apples will be chemical thinning. needed for processing. But As with precision pruning, the thinning process starts by knowing how many fruit buds are on the other end of the on the tree and how many fruit are desired, as Steve Hoying described (see "Achieving the optimal scale, consumers have crop load"). shown their love for fresh, Cornell University horticulturist Dr. Terence Robinson described the process growers might big, red apples in the prices —Terence Robinson follow in chemical thinning. they are willing to pay for With the variety-specific target of final fruit number them. Modern packing plants with high-tech sorters per tree, a precision thinning program is conducted by divide apples into a multitude of niche categories and applying successive thinning sprays and quickly thus extract the highest value from the best apples. assessing the results in time to apply subsequent thinThe question for growers is: Why not produce only the ning sprays, if needed, until the final target fruit biggest, reddest apples? number for each variety is achieved. That question was addressed by speakers at Cornell In practice, this translates into the following steps: University's Precision Apple Management Summit just as 1. Apply a bloom thinning spray at 60 to 80 percent spring was arriving this year. The topic was precision crop of full bloom. load management. 2. Follow this with a petal fall spray two to four days Size matters after petal fall. That would be about one week after the New York State fruit grower Rod Farrow, a speaker on bloom spray when fruits are 5 to 6 millimeters in the program, noted that $5 a box was not an unusual prediameter. mium for apples that vary from each other by a diameter Before applying the petal fall spray, he said, the cardifference of a mere one-sixteenth inch. bohydrate model that Robinson and Dr. Alan Lakso To evaluate thinning effectiveness "Achieving the optimum crop value is often very diffideveloped at Cornell should be used to guide the rate using Duane Greene's fruitlet cult for apple growers," Cornell horticulturist Dr. Terence of chemical and the exact timing of the spray. model, individual apples must Robinson said. "When crop load is reduced to a more The model is at the Network for Environmental and be labeled and measured two moderate size through thinning, crop value rises dramatWeather Applications at the or three times to assess their ically," he said. But yield is also reduced. "Although fruit Web site for use by growers in New York, Massachurate of growth. size continues to increase with crop load reduction, at setts, Vermont, New Jersey, and eastern Pennsylvania. some point it does not compensate for the loss in yield. Extension educators in Michigan and Pennsylvania are "The difference between the optimum crop load and also working with the carbohydrate model to make thinning decisions. underthinning or overthinning can sometimes be a dif3. Assess the efficacy of the first two sprays using the fruit growth rate model developed by Dr. ference of thousands of dollars per acre. More precisely Duane Greene at the University of Massachusetts, which involves measuring growth of specially managing crop load will help growers achieve the optimarked fruit. Research has shown that fruits growing at half the rate of the faster growing fruits will mum crop load and maximize crop value." fall off. Robinson noted that some of the Pacific Northwest's 4. If needed, a third spray is applied when fruit are 10 to 13 millimeters in diameter, or about best orchardists have addressed the situation with very one week after the petal fall spray. Again, the carbohydrate model is used as a guide to determine structured orchards and iron-handed discipline. They the rate of chemical and the exact timing of the third spray. induce branches where they want them, tie them to wires, 5. Lastly, if still more thinning is needed, a fourth spray can be applied at 16 to 20 millimeters, prune each to an exact length and spur number, assign or about one week after the third spray, to achieve the target fruit number. each limb on each trellis wire the task of producing a fixed If still more thinning is needed, hand thinning is called for. —R. Lehnert share of the tree's apples, and they thin to that exact CHEMICAL THINNING is getting more precise S 32 May 15, 2013 GOOD FRUIT GROWER "Achieving the optimum crop value is often very difficult for apple growers."

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