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  • Author or Editor: Richard Marini x
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In five experiments with `Redchief Delicious' and one with `Braeburn', oxamyl (Vydate 2L) was used alone or combined with other chemicals to thin apples. The thinning response to oxamyl depended on dose. In most cases, oxamyl at 600 mg·L−1 and carbaryl at 900 mg·L−1 thinned trees similarly, but the combination of oxamyl plus carbaryl was no more effective than either chemical alone. The combination of oxamyl plus NAA (2.5 to 5 mL·L−1) was slightly more effective than either material alone. The thinning response to oxamyl and carbaryl was related to the concentration of superior oil added to the spray solution; for both chemicals, adding oil at 5 mg·L−1 or Tween 20 at 1.25 mL·L−1 gave equivalent thinning. Apples on trees sprayed with oxamyl plus oil had a dull finish. Adding Tween 20 at 1.25 mL·L−1 improved the thinning activity of carbaryl (Sevin XLR-Plus) more than oxamyl. Similar thinning occurred whether oxamyl was applied when fruit diameter averaged 4 or 10 mm. On `Braeburn' oxamyl, carbaryl, Accel, and NAA were mild thinners, but all combinations of oxamyl or carbaryl plus Accel or NAA overthinned the trees without improving fruit size. In general, oxamyl at 600 mg·L−1 (2 pints of vydate 2L/100 gal.) and carbaryl thin apple trees similarly, and the efficacy of both chemicals is improved by adding a surfactant.

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Six-year-old York/M.9 trees were used to evaluate combinations of chemicals for fruit thinning. In one experiment a factorial combination of 2 levels of carbaryl (0 or 600 mg·L-1) and 5 levels of 6-BA (0, 40, 80, 120, and 160 mg·L-1) were sprayed when fruit diam. averaged 10.5 mm. Carbaryl significantly reduced fruit set, number of fruit/tree, yield efficiency, and crop density, and increased fruit weight. The main effect of 6-BA did not significantly influence any response variable. Two variables were significantly influenced by the carbaryl × 6-BA interaction. In the absence of carbaryl, fruit set was reduced and fruit weight was increased by 6-BA at concentrations less than 160 mg·L-1, but the addition of 6-BA to carbaryl was no more effective than carbaryl alone. In a second experiment, a factorial combination of 2 levels of carbaryl (0 vs. 600 mg·L-1), 2 levels of NAA (0 vs. 5 mg·L-1), and 2 levels of ethephon (0 vs. 450 mg·L-1) were sprayed when fruit when fruit diam. averaged 10.5 mm. Carbaryl and NAA reduced fruit set by about 30%, but ethephon overthinned and reduced set by 65%. When the other materials were combined with ethephon, thinning was similar to ethephon alone. The combination of carbaryl and NAA was no more effective than either material alone. The lowest values for yield, yield efficiency, and numbers of fruit per tree were associated with the combination of ethephon plus NAA. Ethephon was the only material that increased fruit weight.

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Twenty-eight-year-old `Starkrimson Delicious' trees were spur pruned in 1986 and 1987 and/or treated with BA + GA4+7 in 1986 in an attempt to improve spur growth and fruit weight. Yield, fruit weight, and spur quality characters were recorded for 1986-1989. All treatment combinations failed to improve yield or fruit weight. Although spur-pruning improved spur length, spur bud diameter, leaf area per spur and leaf dry weight per spur, fruit weight was not improved. BA + GA4+7 reduced yield and fruit weight, and increased the number of pygmy fruit in 1986, but had little effect on fruiting for the three years after treatment.

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Abstract

Paclobutrazol was applied to soil around 5-year-old ‘Redhaven’ peach [Prunus persica (L.) Batsch] trees at rates of 0, 1.1, 2.2, and 4.4 g a.i./tree in Dec. 1982. Trunk and shoot growth suppression in 1983 were related to application rate, but there was no treatment effect in 1984 or 1985. Yield and fruit size were not influenced in 1983 by treatment, but treated trees produced less fruit than control trees in 1985. Rate of defoliation was negatively related to concentration in 1984, and bloom development was positively related to concentration in 1985 following a single treatment in 1982. Chemical names used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-l,2,4-triazole-1-ethanol (paclobutrazol).

Open Access

Abstract

Trunk cross sectional area (TCA), TCA enlargement, yield, yield efficiency, and terminal shoot length were recorded for each of 10 peach [Prunus persica (L.) Batsch] trees in plantings ranging in age from 4-15 years. Sample variances were used to estimate the number of trees per treatment needed to detect differences of a desired magnitude in experiments comparing 2 treatments. In general, 30 trees per treatment were required to detect a 15% difference in TCA and yield, while more than 40 trees per treatment were needed to detect a similar difference for TCA enlargement and yield efficiency. Twelve trees per treatment and 6 to 22 shoots per tree, depending on cultivar, could be expected to detect a 15% difference in terminal shoot length.

Open Access

The relationship between fruit mass and fruit diameter for apple fruit 2 to 26 mm (0.08 to 1.04 inches) in diameter was evaluated for two cultivars sampled from several orchards for three years. A single regression model was appropriate for all combinations of year, cultivar, and orchard. The model was used to develop a chart to quickly estimate fruit diameter from fruit mass. These fruit diameter estimates can be used by commercial fruit growers to time chemical thinner sprays.

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Abstract

Three peach [Prunus persica (L.) Batsch] cultivars varying in age and vigor were dormant pruned, summer pruned, or summer topped for 2 or 3 years, depending on the cultivar. Pruning treatments had little effect on trunk enlargement and shoot growth of mature 4 Sun queen’ and ‘Loring’ trees. Pruning or topping in June and/or July improved light penetration in tree centers. Pruning or topping in July or June and July stimulated shoot growth of young ‘Cresthaven’ trees more than dormant pruning the season following treatment. Pruning treatment had no consistent effects on yield, fruit size, or date of maturity. Red color and soluble solids of ‘Loring’ fruit were not effected by pruning treatment, but flesh firmness was increased for fruit from summer topped trees. ‘Sunqueen’ fruit quality was effected less by pruning treatment than by crop load, canopy position, or harvest date. Red color and soluble solids were greater for fruit from the tree top and on moderately cropping trees than those from the tree interior or trees with a heavy crop. Harvest date influenced all aspects of fruit quality, but the effects were not consistent for both years.

Open Access

Abstract

Flurprimidol (FP) and paclobutrazol (PB) were applied foliarly to 5-year-old ‘Redhaven’ peach [Prunus persica (L. Batsch)] trees 3 weeks after full bloom, at 0, 500, 1000, 2000, and 3000 ppm. The 2 growth retardants generally affected growth similarly at any given concentration. Shoot growth was suppressed in a linear manner as concentration was increased for both materials the year of application. Only FP suppressed shoot growth the 2nd season following treatment, while both materials enhanced shoot growth the 3rd season following treatment. Both materials suppressed trunk growth for 2 seasons. Yield and fruit size were not significantly influenced by treatments. Yield efficiency was greatest for trees treated at the highest rates of both materials 3 seasons after application. Vegetative and floral bud break on treated trees was advanced the 3rd season after application. Chemical names used: β-[(4-chlorophenyl)methy]-2-(l,l-dimethylethyl)-l-H,2,4-triazole-l-ethanol (paclobutrazol); α-(l-methylethyl)-α-[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol).

Open Access

Abstract

Mature ‘Sunqueen’ peach [Prunus persica (L.) Batsch] trees were dormant pruned, summer pruned, or summer topped for 4 consecutive years. Dormant-pruned trees defoliated slightly earlier than summer-pruned trees, but the onset and duration of terminal vegetative bud rest was not influenced by pruning treatment. Compared to dormant pruning, summer topping slightly reduced cold hardiness of flower buds on 2 of 4 test dates in 1982, but not in 1984. Bloom on vertical shoots in the upper canopy was advanced by summer pruning and by summer topping in both 1982 and 1983. Bloom development at other canopy positions was not influenced by pruning treatment.

Open Access