Hand-thinned Control Research Articles

Net Enclosure of ‘Honeycrisp’ and ‘Gala’ Apple Trees at Different Bloom Stages Affects Fruit Set and Alters Seed Production

Thinning is a critical but challenging practice in apple production, especially for organic producers. The objective of this experiment was to determine if exclusion netting, used to manage insect pests and stress, could reduce fruit set and thinning requirements of ‘Gala’ and ‘Honeycrisp’ apple trees in Michigan and Washington, U.S.A., respectively. Nets were closed around whole canopies at different timings based on a predetermined percentage of open flowers. In 2017 and 2018, netted trees set a full commercial crop regardless of percentage of open bloom at the time of netting, including prebloom enclosures. Fruit set and yield of netted ‘Honeycrisp’ trees were significantly lower than non-netted, nonthinned controls but similar to non-netted hand-thinned controls. ‘Gala’ fruit set and yield did not differ among treatments. Exclusion netting markedly reduced the number of mature seeds and increased the number of nonfertilized seeds in both cultivars. Pollinator exclusion to ‘Gala’ in a frost year increased parthenocarpic fruit set two-fold compared to non-netted trees. Fruit size, shape, and quality attributes of ‘Gala’ were were similar among treatments, but ‘Honeycrisp’ fruit were significantly smaller than hand-thinned, non-netted controls. Netting may constitute an alternative, viable strategy to manage fruit set but requires testing on different cultivars.

Response of Bosc and Cold Snap™ pears to thinning with NAA, 6-BA, ACC, and s-ABA

Adjusting the crop load of European pears (Pyrus communis L.) by hand thinning is currently required to ensure marketable size of most cultivars grown in Ontario. The benefits of thinning pears chemically and its effect on fruit quality and fresh-market returns were investigated in a 3-yr study where a series of foliar chemical thinning sprays were applied during the 10-mm fruitlet stage to Bosc and Cold Snap™ pear trees growing in commercial orchards in the Niagara Peninsula, Ontario. Treatments included an untreated and hand-thinned control and two concentrations each of 6-benzyladenine (6-BA; 75 and 150 mg L−1), naphthalene acetic acid (10 and 20 mg L−1), 1-aminocyclopropane carboxylic acid (150 and 300 mg L−1), and s-abscisic acid (s-ABA; 150 and 300 mg L−1). Overall, all thinning products reduced crop load at least once in the 3-yr study, although this varied by year and cultivar. Higher concentrations were more effective than lower concentrations. Naphthalene acetic acid (both rates), 150 mg L−1 of 6-BA, and 300 mg L−1 of s-ABA were the most consistent at thinning the crop. As the crop load of control trees was not heavy, minimal hand thinning was required and all thinning treatments reduced crop value compared with the untreated trees. There were minimal effects on starch hydrolysis, soluble solids, fruit firmness, and skin colour at harvest.

Managing Apple Crop Load and Diseases with Bloom Thinning Applications in an Organically Managed ‘Honeycrisp’/‘MM.111’ Orchard

Although demand for organic produce continues to increase in the mid-Atlantic, few apple (Malus ×domestica Borkh.) growers in the region have adopted organic management practices due to the considerable disease, insect, and weed pressure, as well as the lack of effective crop load management tools. In this study, lime sulfur (LS) and Regalia® (R) were applied in different sequences (i.e., LS/LS, LS/R, R/R, and R/LS), each in a mixture with JMS Stylet-Oil, to chemically thin apple flowers in an organically managed ‘Honeycrisp’/‘MM.111’ orchard. There was also a nontreated control, a “grower standard” control (LS at 11 mm fruitlet diameter), and a hand-thinned control. The treatments were evaluated for their ability to reduce crop load, as well as to control powdery mildew [Podosphaera leucotricha (Ellis & Everh.) E. S. Salmon], cedar apple rust (Gymnosporangium juniperi-virginiana Schwein.), and quince rust (Gymnosporangium clavipes Cooke & Peck). All treatments reduced crop load compared with the nontreated control, and after the first application of LS or R, the number of fertilized king blooms was reduced and fertilization was prevented in all side blooms. All bloom thinning treatments had more fruit peel russet than the control and russet was more severe when LS was one of the applications. Bloom thinning applications of LS and R did not reduce powdery mildew leaf infection compared with the nontreated control. Cedar apple rust incidence was reduced by all bloom thinning treatments, though some lesions were detected in all treatments. There were minimal quince rust infections in any of the treatments, including the nontreated control. These results suggest that when LS and/or Regalia® are mixed with JMS Stylet-Oil and applied as bloom thinners, they can reduce crop load, and, as a secondary benefit, they can also decrease cedar apple rust incidence from infections that occur during bloom.

Mechanical blossom thinning of ‘Allstar’ peaches influences yield and quality

Peach trees can produce an overabundance of fruit when crop loads are not managed properly, resulting in poor returns due to small fruit size at harvest. Recently, mechanical thinning using string thinners at bloom has been investigated as a method for reducing crop load and labour costs. ‘Allstar’/‘Bailey’ peach trees grown in a supported spindle-type orchard system were subjected to three rates of mechanical blossom thinning (MBT) and hand blossom thinning (HBT) at bloom across two years, with a hand-thinned control added in the second year. Mechanical and hand blossom thinning were both effective in removing flowers and decreasing fruit set with increasing rates. In 2010, only the highest rate of HBT treatment reduced the time needed to hand-thin, but in 2011 nearly all treatments reduced hand thinning labour requirements. Differences in total yield and number of fruit harvested per tree were observed in both years of the study whereas differences in marketable yield were observed only in the first year. The results of this study highlight the benefits of mechanically string thinning peaches at bloom, but also the variability in response across years.

Mechanical flower thinning improves fruit quality of apples and promotes consistent bearing

A novel device is presented for mechanical blossom thinning with first test trials in the US on seven-year-old apple [ Malus domestica (Borkh.)] ‘Buckeye Gala’ near Yakima, WA, USA. Trees were mechanically blossom-thinned with the novel string thinning device, developed by Damerow et al. (2007), at 260 or 360 rpm rotor speeds and a 2.5 km h −1 vehicle speed to improve fruit quality, reduce hand and chemical thinning and to prevent or overcome alternate bearing; manually thinned trees served as controls in a replicated, randomized block trial. The strongest mechanical thinning treatment (360 rpm, 2.5 km h −1) had a positive effect on apple fruit size (75 mm versus 72 mm in the hand-thinned control), firmness 9.0 kg cm −2 versus 8.9 kg cm −2, advanced ripening i.e. starch breakdown, sweetness 12.3-12.8 °Brix versus 11.9 °Brix in the control, contained the largest malic acid content 0.43% versus 0.37% in the control and more red blush, i.e. fruit coloration. The sugar:acid ratio was maintained particularly after the strongest 360 rpm mechanical thinning (29:1) and resembled that of the chemical thinning and the hand-thinned control (32:1), since fruit with higher sugar content also contained more malic acid. The best return bloom was achieved by the conventional chemical standard (105%), followed by the strongest mechanical thinning (92% with 360 rpm) then the combination of mechanical and chemical thinning (85%) compared to much lower values in the control (69%), showing the efficacy of blossom thinning to overcome alternate bearing.

Peach Blossom String Thinner Performance Improved with Selective Pruning

Hand-thinning of fruit is among the most labor-intensive orchard practices and consequently contributes significantly to peach (Prunus persica) production costs. Prior research conducted by the authors on string blossom thinners for managing peach tree cropload demonstrated that this new technology reduces labor requirement and also improves fruit size. Studies were conducted over two seasons in peach orchards trained to perpendicular V or open-center systems to evaluate possible pruning strategies to improve tree canopy access by string thinners. The objectives were to demonstrate if modifications in fruiting shoot orientation, pruning detail, and/or scaffold accessibility improved flower removal, reduced follow-up hand-thinning requirement, and/or increased fruit size. Blossom removal was improved by either detailed pruning or partial pruning (elimination of all shoots on the side of a limb inaccessible by the thinner spindle) in both training systems. Flower density and fruit set measurements revealed greater differences among pruning treatments compared with hand-thinned control treatments with both fruiting shoot orientation pruning modifications and detail pruning resulting in improved thinning. Thinning efficacy was unaffected by scaffold angle but increased as canopy accessibility ranking increased. Follow-up hand-thinning time was reduced by all treatment, system/cultivar, and year combinations except standard pruning in an open center-trained 2009 trial. Detail pruning consistently improved fruit size compared with hand-thinned control and other pruning treatments in both perpendicular V- and open center-trained orchard plots. The best treatments resulted in a thinning savings of $120/ha to $282/ha in perpendicular V plantings and $26/ha to $46/ha in open-center plantings. Realized economic savings beyond hand-thinning alone ranged from $473/ha to $2875/ha in perpendicular V trials and $28/ha to $293/ha in open-center trials.

Performance of Mechanical Thinners for Bloom or Green Fruit Thinning in Peaches

Peach (Prunus persica L. Batsch) thinning is a costly and time-consuming but necessary practice to produce a crop of marketable size fruit. A number of mechanical devices and methods have been developed and evaluated to reduce the cost and time required for hand thinning peach. This report provides additional evidence that a Darwin string thinner can effectively thin peach at bloom and a spiked drum shaker can thin at bloom or at the green fruit (pit hardening) stage. Five trials were conducted over 2 years in grower orchards with trees trained to a perpendicular V system. A Darwin string thinner at 60% to 80% full bloom (FB) reduced crop load (fruit/cm2 limb cross-sectional area) on scaffold limbs by 21% to 50% compared with a hand-thinned control. At the 60% FB stage, a USDA-designed double-spiked drum shaker reduced crop load by 27% and in another trial, a USDA prototype single-drum shaker reduced crop load by 9%. Across all trials, the spiked drum shakers (single or double units) removed an average of 37% of the green fruit. All mechanical devices reduced the time required for follow-up hand thinning. Follow-up hand-thinning costs (US$/ha) were reduced an average of 27% by mechanical thinning devices over hand-thinned control trees. Fruit size was increased over hand-thinned controls by mechanical thinning in most, but not all, trials. A combined treatment of the Darwin string thinner at bloom followed by a drum shaker (single or double unit) at the green fruit stage produced the greatest net economic impact in a number of the trials. Despite overthinning in some trials, the mechanical thinning devices described provide a potential alternative to hand thinning alone in peach production.

Mechanical String Thinner Reduces Crop Load at Variable Stages of Bloom Development of Peach and Nectarine Trees

Thinning of blossoms or fruitlets is a labor-intensive requirement in the production of peach and nectarine (Prunus persica) fruit of optimum size and quality. Prior research conducted by the authors on string blossom thinners for managing peach tree crop load demonstrated that this new technology reduces labor requirement and improves fruit size. The research reported in the current article was conducted over 2 years on ‘Sugar Giant’ peach and ‘Arctic Sweet’ nectarine to evaluate string blossom thinner efficacy at variable stages of bloom development ranging from pink to petal fall. Blossom removal at the pink stage of bloom development was lower than at other stages in 2008; however, a 150-rpm versus 120-rpm spindle rotation speed resulted in blossom removal similar to the 80% full bloom (FB) treatment in 2009. Blossom removal at the petal fall stage was similar to the open bloom stage with the exception of the 2009 ‘Sugar Giant’ trial, in which blossom removal was higher at 80% FB. Flower density and fruit set of the bloom stage compared with hand-thinned control treatments followed a similar trend with the exception that there were fewer differences in 2009 and in lower canopy regions. Follow-up hand thinning time was reduced by all string thinning/year combinations except ‘Arctic Sweet’ at pink in 2008 and 2009 and at petal fall in 2009. The best treatments reduced follow-up hand thinning time compared with green fruit hand thinning alone by 51% and 41% for ‘Sugar Giant’ and by 42% and 22% for ‘Arctic Sweet’ in Years 1 and 2, respectively. In 2008, the percentage of fruit in the “7.0 cm or greater” size category was increased by all bloom stage treatments in both cultivars. The 2009 size distribution of ‘Arctic Sweet’ fruit was unaffected, but the percentage of ‘Sugar Giant’ fruit in higher market value size categories was increased by the 80% FB and higher rpm pink treatments. Savings in hand thinning time and/or increases in fruit size in both years associated with the bloom stage treatments resulted in a net positive impact of $123/ha to 1368/ha compared with hand thinning alone.

String Blossom Thinner Designed for Variable Tree Forms Increases Crop Load Management Efficiency in Trials in Four United States Peach-growing Regions

Hand thinning is a necessary and costly management practice in peach (Prunus persica) production. Stone fruit producers are finding it increasingly difficult to find a workforce to manually thin fruit crops, and the cost of farm labor is increasing. A new “hybrid” string thinner prototype designed to adjust crop load in vase or angled tree canopies was evaluated in processing and fresh fruit plantings in varying production systems in four U.S. growing regions in 2009. Data were uniformly collected across regions to determine blossom removal rate, fruit set, labor required for follow-up green fruit hand thinning, fruit size distribution at harvest, yield, and economic impact. String thinner trials with the variable tree forms demonstrated reduced labor costs compared with hand-thinned controls and increased crop value due to a larger distribution of fruit in marketable and higher market value sizes. Blossom removal ranged from 17% to 56%, hand thinning requirement was reduced by 19% to 100%, and fruit yield and size distribution improved in at least one string-thinning treatment per experiment. Net economic impact at optimum tractor and spindle speeds was $462 to $1490 and $264 to $934 per acre for processing and fresh market peaches, respectively. Case study interviews of growers who thinned a total of 154 acres indicated that commercial adoption of string-thinning technology would likely have positive impacts on the work place environment.

Use of gibberellins on ‘Patterson’ apricot (Prunus armeniaca) to reduce hand thinning and improve fruit size and firmness: Effects over three seasons

Summary‘Patterson’ apricot (Prunus armeniaca) trees were sprayed with an air blast sprayer over three seasons (1992, 1993, and 1994) in three application timings prior to and after harvest, with single sprays of 50, 75, and 100 mg l−1 gibberellic acid (predominantly gibberellin A3 (GA3); Release LC, Abbott Laboratories, North Chicago, IL). A single pre-harvest timing (first week of June) and two concentrations (50 and 100 mg l−1) were consistent across all three years and the effects of these treatments on flowering and fruit development were compared. In all years following treatment with 100 mg l−1 GA, flower numbers per cm of limb length and circumference were significantly reduced. Fruit set was not affected by GA sprays. June 1993 GA sprays of 50 and 100 mg T1 resulted in total yields per tree in 1994 that were equivalent to hand-thinned control trees with 36% and 46% reduction in hand thinning, respectively. Individual fruit weights of fruits treated with 100 mg l−1 GA sprays were equal to those of ...

Bloom Thinning `Loadel' Cling Peach with a Surfactant

Hand thinning fruit is required every season to ensure large fruit size of `Loadel' cling peach [Prunus persica (L.) Batsch] in California. Chemical thinning may lower costs of hand thinning. A surfactant, Armothin {[N,N-bis 2-(omega-hydroxypolyoxyethylene/polyoxypropylene) ethyl alkylamine]; AKZO-Nobel, Chicago; AR}, was sprayed at 80% of full bloom (FB), FB, and FB + 3 days. The spray volume was 935 liters/ha. Concentrations of AR were 1%, 3%, and 5% (v/v). An early hand thinning in late April, a normal hand thinning at 13 days before standard reference date (early May), and a nonthinned control were compared to bloom-thinned trees for set, yield, and fruit quality. AR resulted in no damage to fruit; however, slight leaf yellowing and burn and small shoot dieback were seen at the 5% concentration. Fruit set, and therefore, the number of fruit that had to be hand thinned, were reduced with 3% AR applied at 80% FB and 5% AR applied at all bloom phenophases (stages of bloom development). Thinning time was reduced by 37% (5% AR applied at 80% FB), 28% (5% applied at FB), and by 20% (3% applied at 80% of FB), compared to the normally hand-thinned control. Although AR resulted in early size (cross suture diameter and weight) advantages, at harvest there were no significant differences in fruit size among all AR treatments and the normally hand-thinned control. Total and salable yields of AR treatments and the normally hand-thinned control were equal. Armothin shows promise for chemical thinning of peach when used as a bloom thinner.

Controlling Cropping in `Loadel' Cling Peach Using Gibberellin: Effects on Flower Density, Fruit Distribution, Fruit Firmness, Fruit Thinning, and Yield

Whole-tree sprays of Release LC [predominantly gibberellic acid] (GA,) were applied in a commercial peach [Prunus perisca (L.) Batsch.] orchard in the California Central Valley on three dates from mid-June (about 90 days after full bloom = 28 days before harvest) to late July (14 days postharvest) 1993 at 50, 75, 100, and 120 mg·liter-1. Gibberellin (GA) reduced the number of flowers differentiated in 1993, thereby reducing fruit density in 1994, when sprays were applied by early July 1993. Sprays in late July did not reduce flowering and fruiting density in the following year. In 1994, there were fewer fruit located on the proximal third of the shoot after GA sprays of 75,100, and 120 mg-liter' applied on 15 June compared to hand-thinned controls, and reduction was linear with increase in GA rate. Fruit numbers in the middle and distal sections of shoots were reduced by all 15 June and some 9 July GA sprays, with fewer fruit as concentration increased. However, the distribution of fruit within shoot sections, after GA treatments during floral differentiation, expressed as a percentage of the total number of fruit along fruiting shoots, showed even fruiting compared with hand thinning. Due to reduced flowering in response to GA treatments in June and early July 1993, the hand-thinning requirement was significantly reduced, with no thinning required in 1994 from 15 June 1993 GA sprays. All sprays applied in early July resulted in 40% to 60% fewer fruit removed during thinning than the nontreated controls. Sprays in late July were ineffective. Sprays of GA applied in mid-June at 50,75, 100, and 120 mg·liter and sprays of 120 mg·liter-1 GA applied in early July (4 days preharvest) increased the firmness of `Loadel' cling peach (about 26% improvement in June sprays) in 1993. The salable yield of fruit (after removal of the undersized fruit) was the same on hand thinned and on non-hand thinned trees treated with GA on 15 June at 50 mg·liter-1. The salable yield of fruit was increased by GA sprays of 50 and 75 mg·liter applied on 9 July 1993 compared to controls. There were no differences in fruit size (by weight or diameter) among the aforementioned treatments and hand thinning. GA sprays of 75,100, and 120 mg-liter' applied on 15 June 1993 tended to reduce salable yield, but fruit size increased with decreased yield. Based on the results obtained in 1993 and 1994, we believe that Release LC has good potential for chemically thinning peaches in California.

Chemical Fruit Thinning with Armothin® Sprays to Reduce Fruit Set in `Loadel' Cling Peach

Hand-thinning is required every season to ensure large fruit size of `Loadel' cling peach in California. Hand-thinning is costly. Chemical thinning could help to lower costs of hand-thinning. Armothin® {[N,N-bis2-(omega-hydroxypolyoxyethylene/polyoxypropylene)ethyl alkylamine], AKZO-Nobel, Inc., Chicago; AR} was sprayed at 80% of full bloom (FB), FB and FB + 3 days. The spray volume was 935 liters·ha–1. Concentrations of AR were 1%, 3%, and 5% AR applied at FB. No damage to fruit was noted. Leaf and fine shoot phytotoxicity were seen at 5% AR. The amount of time needed and number of fruits thinned were reduced by those same treatments. Salable yield and fruit size after AR treatments equaled those found on hand-thinned controls. Armothin® shows promise for chemical thinning of peach when used as a bloom spray that damages flowers, thereby reducing fruit set. An experimental use permit was issued for use of AR for stone fruit thinning in California during 1995.

Improving Fruit Firmness and Reducing the Need for Hand-thinning in Peach by using Sprays of Release® LC

`Loadel' cling peach [Prunus persica (L.) Batsch] trees were sprayed with Release® LC (Abbott Laboratories, North Chicago, Ill.) in 1993. Preharvest (harvested 16 July) sprays of 50, 75, 100, and 120 ppm applied on 15 June improved fruit firmness without altering fruit maturity (flesh color by commercial standards) in 1993. In the following 1994 season, flower number per centimeter of shoot length was reduced by sprays ranging from 50 to 120 ppm applied on 15 June and 9 July. No hand-thinning was required on trees treated on 15 June. Trees treated 9 July had 50% fewer fruit removed than on untreated trees, where more than 3000 fruit were removed by hand-thinning. Salable yield was higher than untreated control trees where Release® LC had been applied at 50 ppm on 15 June and 9 July. Fruit size equaled those of hand-thinned controls. As concentration increased on 15 June, salable yield decreased linearly. Fruit size (diameter and individual weight) increased with reductions in salable yield. Interestingly, fruit were evenly distributed along shoots after Release® LC treatment, similar to those found after hand-thinning. Release® LC will be available for commercial chemical thinning of stone fruit in California during 1995. Additional results from peach and other stone fruit will be presented.

Improving Fruit Firmness and Reducing the Need for Hand-thinning in Peach by using Sprays of Release® LC

`Loadel' cling peach [Prunus persica (L.) Batsch] trees were sprayed with Release® LC (Abbott Laboratories, North Chicago, Ill.) in 1993. Preharvest (harvested 16 July) sprays of 50, 75, 100, and 120 ppm applied on 15 June improved fruit firmness without altering fruit maturity (flesh color by commercial standards) in 1993. In the following 1994 season, flower number per centimeter of shoot length was reduced by sprays ranging from 50 to 120 ppm applied on 15 June and 9 July. No hand-thinning was required on trees treated on 15 June. Trees treated 9 July had 50% fewer fruit removed than on untreated trees, where more than 3000 fruit were removed by hand-thinning. Salable yield was higher than untreated control trees where Release® LC had been applied at 50 ppm on 15 June and 9 July. Fruit size equaled those of hand-thinned controls. As concentration increased on 15 June, salable yield decreased linearly. Fruit size (diameter and individual weight) increased with reductions in salable yield. Interestingly, fruit were evenly distributed along shoots after Release® LC treatment, similar to those found after hand-thinning. Release® LC will be available for commercial chemical thinning of stone fruit in California during 1995. Additional results from peach and other stone fruit will be presented.

EVALUATION OF SPRING BARLEYS FOR REACTION TO Fusarium culmorum SEEDLING BLIGHT AND ROOT ROT

The effects of Fusarium seedling blight and root rot, caused by Fusarium culmorum, on plant emergence, harvestable tillers, grain yield and disease reaction in 12 spring barley cultivars were studied in greenhouse and field experiments at Bozeman, Mt. in 1984 and 1985. Atomization of F. culmorum macroconidia onto seed increased disease severity in greenhouse seedlings and mature plants in the field as compared with noninoculated seed. In the inoculated treatments the mean disease rating, based upon the extent of discoloration of the seedling coleoptile or the mature plant subcrown internode, differentiated resistant and susceptible two- and six-rowed cultivars. Among the 12 cultivars, seedling and mature plant disease reactions were not correlated. In 1985 field tests, F. culmorum inoculation reduced the plant emergence of all two-rowed, but only one six-rowed cultivar. Plant emergence in 1985 field tests was negatively correlated with greenhouse seedling and field mature plant disease reactions. To remove the effects of stand reduction by inoculation and determine the subsequent effect of infection on grain yield, the plant stand of a control treatment was hand-thinned to equal that of the inoculated treatment. Generally, F. culmorum inoculation had no effect on harvestable tillers or grain yield when compared with the hand-thinned control. The ease with which seed can be inoculated with the pathogen makes this technique a useful tool in evaluating the ability of a genotype to compensate for stand reduction and to tolerate root rot infection.Key words: Disease tolerance, dryland root rot

Thinning of Peaches by Temporary Inhibition of Photosynthesis with Terbacil

Abstract Greenhouse studies were conducted to identify a chemical that would temporarily suppress net photosynthesis (Pn) of peach leaves. Antitranspirants and photosynthetic inhibitors were tested on leaves of greenhouse-grown peach trees [Prunus persica (L.) Batsch]. Leaf dips of 8% Vapor Gard (poly-1-p-methen-8-9 diyl), 10−3 m ABA, 10−3 m diuron, and 10−3 m terbacil reduced Pn by more than 50% within 1 day after treatment, without causing excessive visual phytotoxicity. Since terbacil strongly reduced Pn with minimal phytotoxicity, it was applied as limb treatments to bearing ‘Madison’ peach trees in the field. Treatments were single applications at 1000 or 2000 ppm, double applications a week apart at 1000 ppm, or 2000 ppm at week 1 followed by 1000 ppm at week 2. Fruit drop was 73% to 90% on terbacil-treated limbs compared to 20% natural drop on nonthinned controls. All terbacil treatments increased the size of remaining fruit over that of the nonthinned checks. The 1000 ppm treatment resulted in fruit size similar to the hand-thinned check, but higher concentrations caused smaller fruit than the hand-thinned control. Chemical names used: abscisic acid (ABA); N’-(3,4-dichlorophenyl)-N,N-dimethylurea (diuron); 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4(1H,3H)-pyrimidinedione (terbacil).

Peach Blossom Thinning with CGA 152811

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’.

The Influence of (2-Chloroethyl)phosphonic Acid on Peach Quality and Maturation1

Abstract Ethephon ((2-chloroethyl)phosphonic acid) at 50 to 200 ppm hastened the maturation of peach fruit of the cvs. ‘Cardinal’, ‘Ranger’, ‘Redhaven’, ‘Blake’, and ‘Richhaven’ over a range of application times. Stimulation of maturation was not attributed solely to reduced fruit load, since an influence on maturation was found even when ethephon-treated trees bore no fewer fruits than hand-thinned controls. When treated and nontreated ‘Richhaven’ fruit were harvested at a comparable maturity based on firmness, ground and flesh color a and a/b values were increased by ethephon, as were soluble solids. No differences were found in b values for ground or flesh color or in total titratable acidity. Fruit treated with ethephon exhibited more uniformity in firmness and color than untreated fruit at shipping maturity, a characteristic which has potential value in facilitating once-over mechanical harvesting operations.