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A study was conducted to determine whether or not the practice of harvesting `Sensation Red Bartlett' (SRB) pear (Pyres communis L.) fruit later than `Bartlett' fruit results in a higher risk of core breakdown development in SRB fruit. Over a range of harvest dates in 2 years of study, incidence of core breakdown in SRB fruit was lower than in `Bartlett' fruit from the same orchard. The disorder increased in both cultivars with longer storage periods, but was usually less in SRB than in `Bartlett'. Core breakdown in both cultivars was more severe in the second year of the study, when lower summer temperatures prevailed. SRB maintained higher fruit firmness on the tree than did `Bartlett'. Accordingly, harvesting SRB later than `Bartlett' appears to be an acceptable practice.

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Abstract

‘Cascade’ is a new red-skinned pear (Pyrus communis L.) that provides a large-fruited red pear for the holiday and late-winter markets. The fruit has excellent dessert quality and sizes well, with heavy cropping.

Open Access

Residues of two fungicides (dodine and fenarimol) and two insecticide/acaricides (amitraz and formetanate) on pear (Pyrus communis L.) leaves were reduced by over-tree sprinkler irrigation applied 24 or 72 hours after pesticide treatment. The difference in residue persistence following over-tree irrigation applied at 24 vs. 72 hours after pesticide treatment was significant only for fenarimol. Residues on leaves from nonirrigated trees at 96 hours post-treatment had declined 24% to 57% from initial levels. Over-tree irrigation further reduced residues by 14% to 47%. For all compounds except dodine, foliar residues measured at 96 hours post-treatment were reduced from initial levels to a greater extent by factors other than over-tree irrigation. Chemical names used: dodecylguanidine monoacetate (dodine); α-(2-chlorophenyl)-α-(4-chlorophenyl)-5-pyrimidinemethanol (fenarimol); N'-(2,4-dimethylphenyl) -N-[[(2,4-dimethylphenyl) imino]methyl] -N-methylmethanimidamide (amitraz); N,N-dimethyl -N'-[3[[(methylamino) carbonyl]oxy]phenyl]methanimidamide (formetanate).

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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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Fruit color of `Sensation' and `Max' Red Bartlett pears was analyzed once at mid-season and three times during later stages of fruit maturity with a Minolta CR-200b portable colorimeter. Color measurements were taken on sun-exposed and shaded fruit surfaces in three different growing locations in Oregon. Color change is nearly constant over time during fruit maturation. Both cultivars gained red and yellow on sun-exposed fruit surfaces, and lost red but gained yellow on shaded surfaces. `Sensation' gained red on sun-exposed surfaces to a greater extent than did `Max' at all locations. `Max' gained more yellow and lost more red on shaded surfaces than did `Sensation'. Differences between cultivars and locations were greater on shaded than on sun-exposed fruit surfaces. Greatest gain in both red and yellow on sun-exposed surfaces was associated with the warmest growing location. Visually perceived color change with maturity appears to be due both to loss of red on shaded surfaces and gain of yellow on all surfaces.

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Abstract

Differential population levels of pear psylla (Psylla pyricola Foerster) and of twospotted spider mite (Tetranychus urticae Koch) were established in ‘d’Anjou’, ‘Bartlett’, and ‘Bosc’ pear (Pyrus communis) trees by application of selective insecticides and acaricides. Numbers of psylla or mites counted were used to calculate psylla days and mite days by averaging numbers per leaf on successive sampling dates and multiplying this average by the number of days between samples. The N concentration of apparently uninjured shoot leaves of ‘d’Anjou’ and spur leaves of ‘Bartlett’ were negatively related to mite days. The reduction in N induced by mites on ‘d’Anjou’ shoot leaves was large enough to affect fertilizer recommendations based on foliar N. Phosphorus concentration was negatively related to mite days in both shoot and spur leaves of ‘d’Anjou’, but not in other cultivars. Other leaf nutrients were not consistently affected. Densities of the pear psylla were not correlated with foliar mineral nutrient concentrations, although high population levels were not established in this study.

Open Access

Tree growth and productivity in 'Doyenne du Comice' ('Comice') pear were not affected by kaolin (Surround WP) treatment programs consisting of applications at 30 or 60 g·L–1 of water applied either three or six times per growing season and repeated for 3 years. In 2 of 3 years, kaolin treatment programs reduced the extent of russet on the fruit surface, although the comparative effectiveness of different concentrations or numbers of applications was not consistent. It appears that kaolin treatment programs can be used in 'Comice' pear production without adverse effects on tree growth and performance. In a relatively high density planting (1098 trees/ha), 'Comice' pear trees growing on Pyrus calleryana rootstock were less yield-efficient and had lower bloom and crop density and fruit set than trees growing on Quince A (Cydonia oblonga) rootstock. Fruit from trees growing on P. calleryana were generally smaller and had less surface russet than did fruit from trees growing on Quince A.

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Mature hedgerows of `Anjou' pear (Pyrus communis L.) trees, planted north(N)-south (S) or east (E)-west (W), were used to study the effect of hedgerow orientation on fruiting and canopy exposure. In 1990, flower bud density tended to be lower on the E-W rows, especially on their N sides. Fruit set (FS) was highest on the S side of E-W rows and lowest on the N side, while the E and W sides of the N-S rows were intermediate. Crop density (CD) had a similar pattern as FS, with more fruit on the S than on the N side of the E-W rows. CD was more evenly distributed between the sides on the N-S hedgerows. Differences in FS and CD between sides were related to different levels of sunlight interception. Light exposure was lowest on the N sides of the E-W rows and highest on the S sides throughout the growing season and especially toward the equinoxes. Increased exposure to the sun on the S and W sides late in the season led to more fruit with solar injury. Fruit from E–W rows were larger and less firm. Accumulated yields over 11 years showed a 21.4% increase in the N-S rows over those of the E-W rows.

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Current N fertilization practices, where high spring applications are utilized, may lead to excessive vegetative growth. However, high rates may not be required to maximize fruit yield and quality. Therefore, alternative strategies to minimize shoot growth while still providing the N needs of the tree were investigated. Mature `Comice' and `Bosc' pear trees were given one of the following treatments: a spring soil (SS) application of NH4NO3 nitrate at 112.5 kg/ha rate, a similar application in the fall after harvest (FS), a fall foliar (FF) spray of a 7.5% urea solution after harvest (FF), or no N (Control). Trees that received a FF application had the same leaf and fruit N content as control trees, but they yielded more fruit The SS application gave more vigorous trees than FF application. Yield, however, was not different.

A 15N enriched urea solution was applied at harvest as either a foliar spray, soil application, or combination of both treatments to mature `Comice' trees. Flower buds from trees that previously received a foliar treatment had 37% of their N derived from the foliar N application. No labeled N was detected in buds from the soil treatment These results indicate that vegetative and reproductive N requirements of fruit trees may be managed separately.

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The brown color development on the skin of three varieties of pears (Bartllet, Packham's T. and Anjou) was characterized between 200 and 300 nm from hexane extracts of pear peel discs, with and without the application of the antioxidant Ethoxyquin (2700ppm) during -1°C storage and 20°C ripening. All the varieties presented a main peak at 232nm (afarnesene), which decreased in the storage as scald increased.

Absorbance at 259, 269, and 280nm (conjugated trienes) were characteristic of Anjou and Packham's Triumph fruits susceptible to the disorder. Bartlett fruits had a major peak at 259nm without the other secondary peaks.

The application of ethoxyquin reduced the oxidation of a farnesene, the formation of the conjugated trienes and intensity of scald in Packham's Triumph and Anjou fruits. However in Bartlett fruits this antioxidant was not very effective to reduce the scald.

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