Search Results

You are looking at 11 - 16 of 16 items for

  • Author or Editor: David Sugar x
Clear All Modify Search

The effects of prohexadione-calcium (P-Ca) on fruit size and return bloom in three pear cultivars were evaluated in Medford and Hood River, Ore., and in Cashmere, Wash. A variety of treatment dosages and timings was applied to 4- and 5-year-old trees in 2 years of study. Fruit weight of `Bosc' and `Red Anjou' pears was not affected by P-Ca treatments at any location in either year. However, decreased weight of `Bartlett' pear fruit was associated with all P-Ca treatments in 1999 in Medford except for 83 ppm applied at 2.5 to 6.0 cm shoot growth (first treatment) plus 2, 4, 6, and 8 weeks after first treatment (WAFT) and 125 ppm applied at 2.5 to 6.0 cm growth plus 4 WAFT. `Bartlett' fruit weight was reduced in Medford in 2000 by all treatments except 125 ppm applied at 2.5 to 6.0 cm growth plus 4, 8, and 12 WAFT. In Cashmere in 2000, mean weight of `Bartlett' and `d'Anjou' fruit was reduced by treatments with 83 or 125 ppm applied at 2.5 to 6.0 cm growth plus 2, 4, and 6 WAFT and of `Bosc' pear by all treatments that included more than a single application of P-Ca. Crop load was not significantly different among treatments at any location. Return bloom in the year following P-Ca treatment was reduced in `Bosc' pears by some to most treatments at all locations in both years. In contrast, return bloom was reduced in `Bartlett' and `Anjou' pears only in Hood River in 1999.

Free access

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.

Full access

The anthocyanin in `Sensation Red Bartlett' pear skin was characterized and quantified, and the effect of light quality on fruit color development was evaluated. Anthocyanin concentration was related to fruit chromaticity values. Pigments were analyzed using high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC). One of two spots detected in the TLC chromatogram did not change color with molybdate sprays, indicating the possible presence of peonidin. HPLC analysis confirmed the presence of a major and a minor pigment, which co-eluted with cyanidin 3-galactoside and peonidin 3-galactoside. Monomeric anthocyanins in the pear skin extract were 6.83 mg/100 g of fruit peel. To study light quality, gelatin filters allowing passage of different wavelengths of-light were attached over the exposed side of `Sensation Red Bartlett' pears 1 month before harvest. Chromaticity was recorded before the filters were attached and after their removal at harvest using the Commission Internationale del'Eclairage (L*, a*, and b*) color space coordinates. Following color measurements, anthocyanin was extracted from individual skin disks. Skin beneath all filters yielded less hue than the control. Wavelengths that transmit above 600 nm had the largest effect on chroma, a*, and b* values. Fruit wrapped in aluminum foil to obscure all light had the highest luminosity. Wavelengths from 400 to 500 nm gave darker, less chromatic, and redder pear fruit. All treatments yielded higher anthocyanin content than the control. There was a tendency toward increased anthocyanin content with longer wavelengths. The simple linear regression of the log anthocyanin content on L* value and (a*/b*) provided an R 2 = 0.41.

Free access

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.

Full access

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.

Full access

Abstract

Putrescine at 10−5, 10−4, 10−3, and 10−2 m applied at anthesis increased fruit set of ‘Cornice’ pear (Pyrus communis L.) in 1985 and 1986. Ovule longevity and the effective pollination period were extended 2 days in 1985 and 5 days in 1986 by putrescine at 10−3 m. Pollen tubes reached the micropyle 2 days earlier in treated than in untreated flowers. High levels of evolved ethylene in flowers were related to pollination and fertilization and were unaffected by putrescine application. Increased ovule longevity and fruit set in treated flowers were associated with increased foliar and flower N and B levels after fertilization. Chemical name used: 1,4-diaminobutane dihydrochloride (putrescine).

Open Access