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  • Author or Editor: David Sugar x
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`Comice' pears (Pyrus communis) harvested early in the maturity range needed 25-31 days of storage at 0 °C to develop the capacity to ripen to an average firmness of 5 lbf within 5 days after being moved to 20 °C. After 24 h exposure to 100 ppm ethylene at 20 °C applied immediately after harvest, 17-27 days additional chilling were needed to develop ripening capacity, while ethylene exposure for 48 hours required an additional 7-17 days chilling. After 72 h ethylene exposure, ripeness was achieved within 5 days following 3 days cold storage, the minimum duration tested. Similar results were obtained when the sequence of ethylene treatment followed by cold storage was reversed. This technique may be applied to reduce the amount of time that `Comice' pears must be stored after harvest before marketing fruit with the capacity to ripen.

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Mancozeb (Manzate 200) and kaolin (Surround WP) were applied individually and in combination in a commercial pear (Pyrus communis) orchard by air-blast sprayer in two growing seasons and in a research orchard by handgun sprayer in four growing seasons. Mancozeb was applied at 50% bloom, petal fall (PF), PF + 2 weeks and PF + 4 weeks, while kaolin and mancozeb + kaolin were applied at PF, PF + 2 weeks and PF + 4 weeks. Both materials reduced russet in both years of the commercial orchard trial and in 2 years of the research orchard trial. In one trial, kaolin treatment reduced russet to a greater extent than did mancozeb, and in one trial the combination of mancozeb plus kaolin reduced russet to a greater extent than either material alone. The year with the greatest amount of russet was the year with the most rainfall, and the year with the least russet was the year with the least rainfall. Considering that mancozeb may be used in pear orchards for suppression of pear scab (Venturia pirina) and pear psylla (Cacopsylla pyricola), and kaolin may be used for suppression of pear psylla, russet reduction by each of these materials adds to their multipurpose utility.

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Management of pear (Pyrus communis L.) trees for low N and high Ca content in the fruit reduced the severity of postharvest fungal decay. Application of N fertilizer 3 weeks before harvest supplied N for tree reserves and for flowers the following spring without increasing fruit N. Calcium chloride sprays during the growing season increased fruit Ca content. Nitrogen and Ca management appear to be additive factors in decay reduction. Fruit density and position in the tree canopy influenced their response to N fertilization. Nitrogen: Ca ratios were lower in fruit from the east quadrant and bottom third of trees and from the distal portion of branches. High fruit density was associated with low N: Ca ratios. Nutritional manipulations appear to be compatible with other methods of postharvest decay control.

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Over-tree sprinkler irrigation cooling treatments were applied to `Sensation Red Bartlett' pear trees during the final 30 days of fruit maturity in 1992 and 1993 when orchard air temperatures were >29 °C. Fruit from cooled trees were more red and less yellow than fruit from noncooled trees, resulting in lower hue values by the middle of the harvestable maturity period in both years of study. In 1992, cooled fruit had a greater portion of the fruit surface covered with red blush than fruit that were not cooled. Fruit firmness decreased more rapidly in fruit from cooled trees than in fruit from noncooled trees, indicating advanced maturity. Accordingly, cooled fruit should be harvested earlier than noncooled fruit to maintain postharvest quality. Differences between cooled and noncooled fruit with respect to hue, surface blush, and rate of firmness loss were more pronounced in a warm season requiring frequent cooling than in a cooler season.

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