Good Fruit Grower

October 2016

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Page 32 of 47 Good Fruit Grower OCTOBER 2016 33 Bitter pit reduction begins at ground level P reventing or mitigating bitter pit in Honeycrisp begins before trees are planted, especially in regions like western New York, where soils tend toward acidity. Applying lime to bring soil pH up to optimal levels — 6 to 6.5 — followed by the right rootstock are the very first steps growers can take to reduce bitter pit incidence. Liming sites before planting is just one more way to increase calcium availability. "I've known grow - ers whose orchards get very acidic by the second or third leaf. Under those conditions, calcium is not fully available to the roots," said Mario Miranda Sazo, Cornell Cooperative Extension fruit specialist. Sample soil from both the topsoil layer — zero to 8 inches — and the subsoil layer, from 8 to 12 inches. "Do it before planting, and that will tell you how much lime you have to apply," he said. Cornell Cooperative Extension personnel also recommend three to four foliar sprays of 1.5 to 2 pounds of 78 percent calcium chloride per 100 gal - lons, at two-week intervals beginning seven to 10 days after petal fall. Follow this with two additional sprays at 3 to 4 pounds of calcium chloride per 100 gallons at four weeks and two weeks prior to harvest. Rootstock plays an important role in bitter pit susceptibility as well. "Based on data I've seen in the NC-140 trials, Honeycrisp trees on Bud 9 seem to have less bitter pit than those on M.9 or M.26," said Lailiang Cheng, Cornell University horticulture associate professor. —D. Weinstock nutrients, such as phosphorus, potassium and magne- sium. He also wanted to evaluate Honeycrisp fruit with and without bitter pit, comparing nutrient levels in both the peel and the cortex. So he and Miranda Sazo found a block of Honeycrisp with moderate amounts of bitter pit alongside a Gala block with no bitter pit at all in western New York. They took leaf and fruit samples from both and analyzed them. An imbalance They duplicated the results of Cheng's 2009 study that Honeycrisp leaves had even higher calcium levels than Gala leaves. In addition, they found Honeycrisp leaves had lower levels of phosphorus, potassium and magnesium. Next, they looked at the fruit samples. They separated the peels from the cortex tissue and analyzed them for the presence of nutrients. "The first thing that caught my eye was in both the cortex and peel tissues, Honeycrisp fruit had only half the calcium that Gala had," Cheng said. In Gala and Honeycrisp cortex tissue, they found no significant differences in the potassium, magnesium or phosphorus levels. Once they examined Honeycrisp peel tissues, however, they found almost 50 percent higher levels of potassium and phosphorus. Then they calculated the ratios of potassium to calcium and phosphorus to calcium. Both were much higher in Honeycrisp than in Gala, which Cheng said depicted a nutrient imbalance associated with bitter pit susceptibility. Visually healthy peels on Honeycrisp apples with bitter pit had lower calcium content than those Honeycrisp free of the disorder, but had higher concentrations of potas- sium and phosphorus. Pitted peels had the lowest calcium level and the highest concentrations of potassium and phosphorus. The pattern was clear. Wherever potassium levels were higher, calcium levels were lower. And because they observed the level differences in peels and not the cortex, Cheng and Miranda Sazo think peel nutrient analysis is a far better indicator of bitter pit development than calcium levels in the cortex. "Peel nutrient levels are very consistent with bitter pit develop- ment," Cheng said. • • Enter different row spacings: the controller automatically maintains your rate per acre. • Compensates for changes in ground speed. 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