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  • Author or Editor: D. W. Greene x
  • Journal of the American Society for Horticultural Science x
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Abstract

A 3-year study was undertaken to compare the effectiveness of mechanical and chemical techniques to enhance flower bud initiation and fruit set on young ‘Delicious’ apple trees (Malus domestica Borkh. Scoring, limb spreading, and growth regulators predictably reduced terminal growth, but only scoring consistently increased bloom. When bloom was increased, fruit set did not always follow. The most effective treatment for increasing fruit set was (2-chloroethyl)phosphonic acid (ethephon) at 1000 ppm plus 1000 ppm succinic acid-2,2-dimethylhydrazide (daminozide). Combination sprays of ethephon plus daminozide show promise for restricting vegetative growth of non-bearing ‘Delicious’.

Open Access

Abstract

Applications of (2-chloroethyl)phosphonic acid (ethephon) on ‘McIntosh’ apple trees (Malus domestica Borkh.) in early August at concentrations of 125 to 500 ppm promoted the climacteric rise in respiration, increased soluble solids, fruit abscission, and red color, and also reduced flesh firmness. Results from ethephon applications in July were variable; in 1974 July applications were more effective, and in 1975 less effective, than treatments applied in early August. The effects of ethephon were reduced when 1000 ppm succinic acid-2,2-dimethylhydrazide (daminozide) was combined with the ethephon. No treatment influenced repeat bloom or set the year following application.

Open Access

Abstract

Sprays of (2-chloroethyl)phosphonic acid (ethephon) applied to ‘Delicious’ apple trees (Malus domestica Borkh.) in July at concentrations of 500 to 1000 ppm shortly after the completion of June drop hastened the respiratory climacteric, and increased soluble solids, watercore and preharvest drop. These effects were diminished when 1000 ppm succinic acid-2,2-dimethyhydrazide (daminozide) was included with ethephon. All concentrations of ethephon increased flesh firmness. Two periods of fruit abscission occurred following ethephon application at high concentrations: shortly after application and immediately prior to harvest. After cold storage, fruit which had received 500 or 1000 ppm ethephon had less scald but a greater incidence of brown core. High ethephon concentrations increased bloom the following spring but had no influence on fruit set.

Open Access

Abstract

Factors influencing the foliar penetration of naphthaleneacetamide (NAAm) were established by following penetration from a glass vial into pear leaf discs (Pyrus communis L. cv. Bartlett). Penetration through the upper surface was linear for 96 hr, whereas, through the lower surface there was rapid penetration for 48 hr followed by a reduced rate. Uptake of NAAm was proportional to the concentration applied. Penetration was not influenced by pH of treatment solutions ranging from 3.0 to 7.0. Increasing temperature from 5–35°C caused a marked increase in penetration with Q10 values ranging between 1.59 to 5.46. Increasing light intensity resulted in increased penetration through the lower surface up to about 300 ft-c, but had no effect on NAAm penetration through the upper surface. Penetration was greater through the upper than lower surface in expanding leaves, but the reverse was true when leaves were fully expanded. Tween 20 and Triton B-1956 (0.1%) increased NAAm penetration through the lower surface, but to a lesser degree than X-77 (0.1%). No surfactant studied enhanced penetration through the upper surface. Penetration from microdroplets was similar to that from solutions in glass cylinders until the droplets dried. Droplet drying resulted in an immediate increase in penetration.

Open Access

Abstract

Ethephon [(2-chloroethyl) phosphonic acid] at rates of 100 to 1000 ppm caused fruit abscission of apples (Malus pumila Mill. cv. Cortland and Mutsu) when applied 26 to 44 days after full bloom. Ethephon alone or in combination with SADH (succinic acid 2,2-dimethylhydrazide) caused fruit abscission of ‘Early McIntosh’ when applied 30 days after full bloom. When sprayed shortly after completion of June drop, no abscission occurred. Although no fruit abscission followed the post-June drop treatment, flower bud initiation was increased. SADH appeared to enhance the fruit abscission capabilities of ethephon.

Open Access

Abstract

Annual applications of 2,6-dichlorobenzonitrile (dichlobenil) for 6 consecutive years at recommended rates caused yellowing of apple leaf margins (LMY). LMY appeared in mid-June or later and increased in severity as the season progressed. Severity of LMY was positively associated with individual trees throughout the study. Comparisons between control and dichlobenil-treated trees showed no differences in tree growth and yield, although they were sometimes negatively correlated with LMY severity.

Open Access

Abstract

Red color development of ‘McIntosh’ apples that previously received a mid-July application of succinic acid 2,2-dimethylhydrazide (SADH) and were then treated before harvest with 2-chloroethylphosphonic acid (ethephon) occurred earlier and more extensively than on controls. Fruit receiving 150 or 250 ppm ethephon were less firm within 7 or 8 days than fruit receiving only SADH. The respiratory climacteric was advanced 6 to 10 days by ethephon treatments as low as 25 ppm. Naphthaleneacetic acid (NAA) was less effective than 2,4,5-trichlorophenoxypropionic acid (fenoprop) in preventing preharvest drop, especially at higher ethephon concentrations. Fruit from all treatments kept well in both CA and air storage provided they were in good condition at harvest. Scald developed to a greater extent on stored fruit that had received ethephon than on controls.

Open Access

Mature peach trees were grown in six different-sized vegetation-free areas (VFAs) (0.36 to 13 m2) with and without stage 3 drip irrigation for 6 years. As VFA size increased, so did the trunk cross-sectional area, canopy diameter, total yield/tree, large fruit yield/tree, and pruning weight/tree. The yield efficiency of total fruit and large fruit initially increased with the increasing size of VFAs and then remained stable over the range of VFAs. Applying supplemental irrigation increased yield of large fruit and leaf N percentage in all VFAs. Cold hardiness was not affected by VFA size or irrigation treatment. The smaller VFAs resulted in smaller, equally efficient trees. Sod management was an effective, low-cost approach to controlling peach tree size, and, when combined with irrigated, high-density production, potentially increased productivity.

Free access

Abstract

Preharvest sprays of aminoethoxyvinylglycine (AVG) drastically suppressed internal ethylene concentrations, and delayed or prevented ripening of ‘McIntosh’, ‘Spartan’, and ‘Spencer’ apples (Malus domestica Borkh.) at room temperature (ca. 25°C) after harvest, the magnitude of delay varying with cultivar and with AVG concentration. However, after treated fruit had been stored with untreated fruit at 0°C, little or no difference in ripeness was discernible between treated and untreated samples. Internal ethylene concentrations in treated fruit after storage were much less than in controls but generally exceeded 1 ppm. Infiltration of ripe fruit with AVG severely suppressed ethylene production, but 2 minute dips in AVG solutions had no effect until after prolonged time in storage.

Open Access

Abstract

Residual effects of single applications of 1000 and 2000 ppm succinic acid 2,2-dimethylhydrazide (SADH) in mid-July or mid-August, 1969, were determined. Mid-August treatment of 2000 ppm SADH inhibited June drop, depressed fruit size and increased fruit set; but it did not affect flowering, seed content and viability during June drop, preharvest drop, flesh firmness, or yield in 1970. Flowering and yield were often reduced in 1971 where SADH was applied in 1969. The results suggest that under some circumstances the residual effects of SADH may tend to induce biennial bearing of ‘McIntosh’ apple trees.

Open Access