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Hand-thinning (Prunus persica L. Batsch) “Y”-trained peach trees at bloom and 51 days after full bloom (DAFB) was compared to mechanical fruit thinning 51 DAFB using a spiked-drum and an impact shaker. The spiked-drum shaker removed more fruit from horizontal branches than from vertical branches, yet did not selectively remove either large or small fruit. Bloom thinning by hand increased fruit size compared to postbloom thinning 51 DAFB, and both postbloom mechanical thinning techniques were as effective as postbloom hand thinning. The spiked-drum shaker may be a better thinning technique than the impact shaker because it transfers less shaking energy to the fruit, can be used in high-density plantings, and does not contact the trunk, lessening the potential for tree damage.

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axillary shoots in free-branching cultivars was identified to be an unculturable phytoplasma ( Lee et al., 1997 ). In free-branching cultivars, thinning of surplus shoots could be an additional procedure to control growth and to achieve crop uniformity

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Chemicals being tested for bloom thinning of apples are effective for bloom thinning of stone fruit. Sulfcarbamide (Wilthin) and Endothall applied to peaches, nectarines, and apricots at 90% of bloom open reduced fruit set by 50%. Fruit size and quality of crop were improved. Slight phytotoxicity occurred on leaves and twigs, but no injury occurred on fruit. Two years of data will be presented and comparisons will be made with other new thinning agents.

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broken limbs due to the excess weight of fruit, and ensuring adequate return bloom to minimize biennial bearing ( Byers, 2003 ; Dennis, 2000 ). Thinning, or reducing the number of apples per tree and within each fruiting cluster, can also decrease

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Abstract

A single-value estimate of maturity response and an independent estimate of the thinning response to treatment can be determined from detailed harvest records. Thinning index is estimated from the total number of fruit per tree; maturity response is estimated from the weighted-average harvest date.

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A carbaryl spray thinned fruit of the apple (Malus svlvestris (L.) Mill.) cv. Red Rome but did not affect ethylene evolution of fruit or pedicel of ’Red Rome’, ‘Golden Delicious’ or ‘Staymared’. It did increase ethylene evolution of the leaves of the first 2 compared with ‘Staymared’ even though ‘Red Rome’ was the only cultivar thinned by the Sevin spray. Naphthaleneacetic acid (NAA) sprays which caused thinning also increased ethylene evolution of all 3 structures, commencing the second day after application. The increase was greater than that from dipping samples structures in the same solution. Covering branches with black shading cloth reduced ethylene evolution of mature to young apple leaves. Lack of good correlation between thinning, ethylene evolution of different structures, and methods of application make it desirable to develop a better method of screening potential apple thinning materials.

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evaluate the impacts of renewal pruning, where all stems were removed to the ground, and thinning, where the number of stems was reduced the following year, on plant re-growth, time to resumption of fruit production, and fruit quality and yield. Plants

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‘Schley’ pecan [Carya illinoensis (Wang.) K. Koch] fruit were selectively thinned within one week after treatment with (2-chloroethyl)phosphonic acid (ethephon) without causing leaf abscission. A concentration range of 25, 50, 75, 100, 150, and 200 ppm caused progressive and selective fruit thinning ranging from 25 to 75%, depending upon concentration and fruit age. Fruit treated when at 4-mm diameter (June 15) were more heavily thinned at the same rate than fruit at 12-mm diameter (July 15). Leaf abscission occurred at rates of 300 ppm or greater on each treatment date. Ethephon levels had no effect on return bloom or fruit set.

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Adequate fruit thinning of ‘Loring’ peach [Prunus persia (L.) Batsch] was achieved with single applications of (2-chloroethyl)-methylbis (phenylmethoxy) silane (CGA 15281) at concentrations of 240, 360, and 480 ppm applied at seed length of 8.8 mm and 2 applications at 240 and 360 ppm applied 7 days apart at 8.8 and 10.8 mm seed lengths in 1978. Additional hand thinning following treatment was required. In 1979 adequate thinning was achieved with 1 application of 240 ppm applied at seed length of 13.9 mm or 480 ppm applied at an 8.5-mm seed length. Yields from these treatments were reduced but did not differ from the control treatment. Multiple applications and higher rates resulted in over-thinning and reduced yields. The sensitivity of fruit to thinning appeared to increase with increased seed length. In 1978, foliage injury occurred at all rates and the severity of injury increased at higher concentrations and multiple applications. However, no foliage injury was observed in 1979.

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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’.

Open Access