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- Author or Editor: Gerard W. Krewer x
Observations in controlled field experiments over 5 years indicated that imidacloprid, applied as a soil drench around the trunks of peach (Prunus persica), nectarine (P. persica var. nectarine) and japanese plum (P. salicinia) trees at planting and in the early spring and mid-summer for two subsequent seasons (0.7 g/tree a.i.), slowed the development of symptoms of phony peach disease (PPD) and plum leaf scald (PLS) (Xylella fastidiosa) in the trees. After 3.5 years, the percentage of peach trees showing PPD symptoms was 8.5% for the imidacloprid-treated trees compared to 34.3% for untreated trees. After 4.5 years, the percentage of peach trees showing PPD symptoms was 13.1% in the treated trees and 71.4% in the untreated trees. After 3.5 years, nectarine trees in untreated and treated plots showed PPD symptoms in 8.3% and 0.9% of the trees, respectively. After 4.5 years, PPD symptoms in nectarine were found in 32.3% of the untreated trees and 8.5% of the treated trees. Development of PLS disease in plum was also slowed by the trunk drench with imidacloprid in two japanese plum varieties. After 3.5 years, dieback was observed in 55% of the twigs of untreated and 23% of the twigs of treated trees of `Au Rosa' plum and 33% of the twigs of untreated and 12% of the twigs of treated trees of `Santa Rosa' plum.
Abstract
There was an inverse linear relationship between fruit set of ‘Bicentennial’ and ‘Redhaven’ peach trees [Prunus persica (L.) Batsch] and treatments of 0 − 4000 ppm of (2-chloroethyl)methylbis(phenylmethoxy) silane (CGA 15281) in 1980. Increases in fruit weight occurred at the highest rate of CGA 15281 when compared to lower rates with ‘Bicentennial’, but no significant increase was obtained with ‘Redhaven’. Terminal fruit were larger than basal and middle node position fruits in ‘Bicentennial’. In 1981, all applications of CGA 15281 (0 − 3000 ppm) to ‘Candor’ and ‘Jefferson’ thinned blossoms and resulted in an increase in fruit size, when compared to the hand-thinned control. Treatments of 2250, 2500, and 2750 ppm to ‘Candor’ resulted in adequate thinning and increased yields. Applications at 1500 and 1750 ppm resulted in overthinning and reduced yields in ‘Jefferson’.
Abstract
‘Spalding’ pear (Pyrus sp. Nak) has been released to provide a good quality pear cultivar for home planting in the Piedmont area of the southeast where fire blight is a major problem.
Abstract
Fruit tissue only was treated with concentrations of 0, 240, 360, 480, 600, 720, 840, and 960 ppm of (2-chloroethyl)methyl bis (phenyl methoxy) silane (CGA 15281) applied to 1/3, 1/2, and 2/3 of the fruit surface. Increased abscission of fruit occurred as ovule length increased from 3.5 mm to 13.3 mm when fruit alone were treated. Foliage sprays of the same concentrations with the fruit protected generally had no effect on fruit or leaf abscission. Application of 0.01 ml droplet of CGA 15281 to the abscission zone, peduncle, and fruit cheek caused little fruit removal, but produced chlorosis of the treated area on the fruit. The data suggest that fruit contact with CGA 15281 is necessary for fruit thinning.
Northern highbush (NH) blueberry (Vaccinium corymbosum) and southern highbush (SH) blueberry (V. corymbosum hybrids) have fruit that vary in firmness. The SH fruit is mostly hand harvested for the fresh market. Hand harvesting is labor-intensive requiring more than 500 hours/acre. Rabbiteye blueberry (V. virgatum) tends to have firmer fruit skin than that of NH blueberry and has been mostly machine harvested for the processing industry. Sparkleberry (V. arboreum) has very firm fruit. With the challenges of labor availability, efforts are under way to produce more marketable fruit using machine harvesting. This could require changing the design of harvesting machine and plant architecture, and the development of cultivars with fruit that will bruise less after impact with hard surfaces of machines. The objectives of this study were to determine the fruit quality of machine-harvested SH blueberry, analyze the effect of drop height and padding the contact surface on fruit quality, investigate the effect of crown restriction on ground loss, and determine the effect of plant size on machine harvestability. The fruit of ‘Farthing’, ‘Scintilla’, ‘Sweetcrisp’, and several selections were either hand harvested or machine harvested and assessed during postharvest storage for bruise damage and softening. Machine harvesting contributed to bruise damage in the fruit and softening in storage. The fruit of firm-textured SH blueberry (‘Farthing’, ‘Sweetcrisp’, and selection FL 05-528) was firmer than that of ‘Scintilla’ after 1 week in cold storage. Fruit drop tests from a height of 20 and 40 inches on a plastic surface showed that ‘Scintilla’ was more susceptible to bruising than that of firm-textured ‘Farthing’ and ‘Sweetcrisp’. When the contact surface was cushioned with a foam sheet, bruise incidence was significantly reduced in all SH blueberry used in the study. Also, the fruit dropped 40 inches developed more bruise damage than those dropped 20 inches. Ground loss during machine harvesting was reduced from 24% to 17% by modifying the rabbiteye blueberry plant architecture. Further modifications to harvesting machines and plant architecture are necessary to improve the quality of machine-harvested SH and rabbiteye blueberry fruit and the overall efficiency of blueberry (Vaccinium species and hybrids) harvesting machines.