Crop Load Reduction and Fruit Size Following Multi-step Thinning of 'Empire' Apple

Two years of field experiments were conducted in eastern New York to evaluate the efficacy of a multi-step thinning approach on reducing crop load (no. fruit per cm2 trunk cross-sectional area) and increasing fruit size of 'Empire' apple (Malus ×domestica Borkh.). Applications of Endothall (ET) at 80% bloom, NAA + carbaryl (CB) at petal fall (PF), and Accel™ + CB at 10 mm king fruitlet diameter (KFD), alone and in all combinations, were compared to a nonthinned control and to the application of NAA + CB at 10 mm KFD (commercial standard). In both 1996 and 1997, orthogonal contrasts indicated the multi-step treatment significantly increased fruit size, reduced cropload, and reduced yield compared to single applications. Effects on cropload of consecutive treatments were largely predicted by multiplying effects of individual treatments. Although all thinning treatments except for NAA + CB at PF in 1997 significantly reduced cropload, no single treatment thinned sufficiently to ensure good return bloom. Compared to NAA + CB at 10 mm KFD, multi-step thinning with NAA + CB at PF followed by Accel™ + CB at 10 mm KFD produced bigger fruits in both years, and resulted in a higher percentage of spurs carrying a single fruit in 1996. When fruit size was evaluated after removing the effect of cropload (cropload adjusted fruit weight), NAA + CB at PF, Accel™ + CB at 10 mm, and the two applied sequentially, resulted in greater cropload adjusted fruit weight than the nonthinned control in both years, whereas NAA + CB at 10 mm did not. Contrast analysis of treatments with and without ET showed no significant effect of including ET on fruit size, though total cropload was reduced at P = 0.10 and total yield was reduced (P = 0.03 in 1996 and P = 0.12 in 1997). No deleterious effects from multi-step treatments have been observed. All thinning treatments significantly increased return bloom in 1996 and 1997 compared to the control with little difference observed between treatments. Chemical names used: naphthalene acetic acid (NAA); 1-naphthyl-N-methylcarbamate [carbaryl (CB)]; 6-benzyladenine [BA (Accel™)]; 7-oxabicyclo (2,2,1) heptane-2,3 dicarboxylic acid [ET (Endothall™)]

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Interaction Between CPPU and NAA on Fruit Thinning and Fruit Development in Selected Apple Cultivars

HortScience ◽

10.21273/hortsci.33.3.513c ◽

1998 ◽

Vol 33 (3) ◽

pp. 513c-513 ◽

Cited By ~ 1

Author(s):

Martin J. Bukovac ◽

Jerome Hull ◽

John C. Neilsen ◽

Michael Schroeder ◽

Georg Noga

Keyword(s):

Total Yield ◽

Fruit Size ◽

Frost Damage ◽

Fruit Growth ◽

Soluble Solids ◽

Seed Number ◽

Crop Load ◽

Fruit Thinning ◽

Carpel Development ◽

Return Bloom

NAA is used extensively for fruit thinning of apples to increase fruit size and to promote return bloom. In some cultivars, even if thinning is achieved, fruit size at harvest may be less than expected based on crop load. CPPU, N-(2-chloro-4-pyridinyl)-N.-phenylurea, has been shown to increase fruit growth in apples, grapes, and kiwi. We evaluated combinations of NAA and CPPU on thinning, fruit growth and return bloom in Redchief `Delicious', `Elstar', and `Gloster'. CPPU was applied at 5 mgμL–1 (based on 0 to 10 mgμL–1 response curve) in combination with 15 mgμL–1 NAA as high-volume sprays at 7 to 10 mm KFD. Yield and fruit size distribution (on total yield) were used as index of response. In `Delicious', CPPU (3-year study) increased % large (70 mm+) fruit, but in the presence of NAA % large fruit was reduced 2 of the 3 years. CPPU did not induce significant thinning. There were no significant effects on color or soluble solids; firmness was increased slightly and seed number reduced. The L/D ratio was increased and uneven lobe and carpel development was common. CPPU had no significant effect on return bloom in presence or absence of NAA, but NAA increased bloom in both the presence and absence of CPPU. With `Elstar' (2-year study) there was no significant thinning with either chemical, but CPPU increased mean fruit size and % large (70–80 mm) fruit over nonthinned, but not significantly greater than NAA alone. There were no significant differences in firmness, color, soluble solids or seed number. NAA + CPPU did not inhibit fruit growth or cause excessive uneven carpel development. Frost damage reduced crop load in `Gloster' where results were similar to `Elstar' except seed number was reduced by the NAA + CPPU combination.

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Black Polyethylene Mulch Doubled Yield of Fresh-market Field Tomatoes

HortScience ◽

10.21273/hortsci.27.7.787 ◽

1992 ◽

Vol 27 (7) ◽

pp. 787-789 ◽

Cited By ~ 16

Author(s):

Aref Abdul-Baki ◽

C. Spence ◽

R. Hoover

Keyword(s):

Field Experiments ◽

Total Yield ◽

Fruit Size ◽

Fruit Weight ◽

Planting Date ◽

Trickle Irrigation ◽

Fresh Market ◽

Planting Dates ◽

Early Production ◽

Polyethylene Mulch

Field experiments were conducted to a) maximize total yield of fresh-market field tomato (Lycopersicon esculentum Mill.) cultivars using black polyethylene mulch (BPM), and b) increase fruit size and yield during the last 5 weeks of the production period by reducing the number of synthate sinks per plant through eliminating all flowers that appeared during this period. Unmulched treatments under trickle irrigation and multiple applications of soluble fertilizer yielded an average of 43 t·ha-1 for `Sunny' and `Pik-Rite' over the two planting dates. With BPM, total yield increased by 95% to 84 t·ha-1. Although total yield increases due to BPM over the control were highly significant in both cultivars and over the two planting dates, yield increases were higher for the early than for the optimum planting date. BPM also significantly increased early production of `Pik-Rite' but not `Sunny', and the increase in early production was more pronounced for the optimum than the early planting date. Sink reduction during the last 5 weeks of the growing season had no effect on yield or fruit weight during that period.

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The Effects of Exogenous Bioregulators and Environment on Regular Cropping of Apple

HortScience ◽

10.21273/hortsci.33.3.554e ◽

1998 ◽

Vol 33 (3) ◽

pp. 554e-555

Author(s):

Kathleen M. Williams

Keyword(s):

Pacific Northwest ◽

Cultural Practices ◽

Negative Impact ◽

Fruit Size ◽

Physiological Status ◽

Naphthalene Acetic Acid ◽

Crop Load ◽

The Past ◽

The Pacific ◽

Return Bloom

Use of exogenous bioregulators (“hormones”) to adjust crop load in apple remains challenging to both researchers and producers. These hormones are sensitive to the rate and timing of application, to the physiological status of the tree, the choice of orchard system, variety and rootstock, and a myriad of cultural practices and environmental factors. All classes of plant bioregulators have been used over the past 30 to 40 years as chemical thinning materials. Most of the standard postbloom thinning programs involve application of a synthetic auxin, such as naphthalene acetic acid (NAA) in combination with carbaryl, a commonly used insecticide. The mode of action of these two compounds is not clearly understood. Gibberellins generally have not been effective thinning materials because of the negative impact on return bloom. Ethylene-releasing compounds have been used successfully as postbloom thinning materials. And cytokinins, particularly synthetic sources such as 6-BA, have been shown to effectively thin fruit and to enhance fruit size on many commercial varieties. The rate and timing of 6-BA applications are particularly critical to obtain the desirable thinning and size responses. Overall, these bioregulators are sensitive to temperature. The use of bloom thinning compounds and their efficacy in the Pacific Northwest will be discussed in the context of return bloom.

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Tree Growth, Fruit Size, and Yield Response of Mature Peach to Weed-Free Intervals

Weed Technology ◽

10.1614/wt-06-002.1 ◽

2007 ◽

Vol 21 (1) ◽

pp. 102-105 ◽

Cited By ~ 5

Author(s):

Andrew W. MacRae ◽

Wayne E. Mitchem ◽

David W. Monks ◽

Michael L. Parker ◽

Roger K. Galloway

Keyword(s):

North Carolina ◽

Total Yield ◽

Fruit Size ◽

Fruit Weight ◽

Yield Response ◽

Peach Tree ◽

Cross Sectional ◽

Common Lambsquarters ◽

Smooth Pigweed ◽

Large Crabgrass

An experiment was conducted at one location in 1999 and two locations in 2000 to determine the critical weed-free period for peach in North Carolina. The cultivars for the three locations were ‘Contender’, ‘Norman’, and ‘Summerprince’. Weed-free intervals of 0, 3, 6, 9, 12, and 15 wk after peach tree bloom were established. Paraquat at 1.1 kg ai/ha plus nonionic surfactant at 0.25% v/v was applied every 10 d, after treatments were initiated at peach bloom, to maintain weed-free plots. Large crabgrass, hairy vetch, and smooth crabgrass were the primary weeds in Contender. Horseweed, smooth crabgrass, and large crabgrass were the primary weeds in Norman. Bermudagrass, smooth pigweed, and common lambsquarters were the primary weeds in Summerprince. No differences in trunk cross-sectional area were observed between the weed-free periods. Maintaining the orchard floor weed-free for 12 wk after peach tree bloom resulted in the greatest fruit size (individual fruit weight and diameter), total yield, and fruit number.

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Crop Load, Fruit Thinning and their Effects on Fruit Quality of Apple (Malus domestica Borkh.)

Acta Agraria Debreceniensis ◽

10.34101/actaagrar/24/3221 ◽

2006 ◽

pp. 29-35 ◽

Cited By ~ 2

Author(s):

József Racskó

Keyword(s):

Growth Rate ◽

Fruit Quality ◽

Fruit Size ◽

Flower Initiation ◽

Pome Fruit ◽

Cross Sectional ◽

Crop Load ◽

Fruit Thinning ◽

Return Bloom ◽

Tree Leaf

Crop load, a quantitative parameter used by industry, is generally defined as the number of fruit per tree. It is often expressed in terms of number of fruit per trunk cross-sectional area (fruit/TCSA). Crop load is the most important of all factors that influence fruit size, and the removing of a part of the crop is the most effective way to improve fruit size.The potential size of a given pome fruit is determined early in the season and growth proceeds at a relatively uniform rate thereafter. This uniform growth rate permits the accurate prediction of the harvest size of the fruit as early as mid-summer. The growth rate, once established, is not easily altered, and fruit numbers, therefore, can affect fruit size only within definite limits and maximum effectiveness requires adjustment in fruit numbers relatively early in the season. It was established, that „thinning does not change a potentially small fruit into a large fruit, but rather insures that a potentially large fruit will size properly.” Emphasis should be on estimating fruit numbers rather than fruit size.Fruit thinning can quickly reach the point of diminishing returns. Rather than a high percentage of large fruits, the objectives of thinning should be the elimination of the smallest fruits, improved fruit quality and annual production. Fruit thinning is accomplished by hand or chemical thinning. Chemical thinners are separated into categories as bloom thinners and post-bloom thinners. Early removal of potential fruit (blossom thinning) is currently used in many apple producing areas to enhance flower initiation for next year’s crop and thus, return bloom. It also results in reduced competition for photosynthates. Blossom thinners usually have a caustic effect on floral parts.The amount of fruit left on a tree should be determined by the vigor and general condition of the tree. Leaf area per fruit affects the number of spurs flowering the following season. It can be difficult to separate timing and fruit number effects in crop loading studies, as abscission rates after hand thinning of retained flowers/fruitlets tend to very with the time of hand thinning.

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Blossom and Fruitlet Thinners Affect Crop Load, Fruit Weight, Seed Number, and Return Bloom of `Northern Spy' Apple

HortScience ◽

10.21273/hortsci.39.6.1309 ◽

2004 ◽

Vol 39 (6) ◽

pp. 1309-1312

Author(s):

Douglas Nichols ◽

Charles Embree ◽

John Cline ◽

Hak-Yoon Ju

Keyword(s):

Mineral Oil ◽

Fruit Weight ◽

Hydroxybenzoic Acid ◽

Apple Cultivar ◽

Seed Number ◽

Full Bloom ◽

Cross Sectional ◽

Crop Load ◽

Year Effect ◽

Return Bloom

To determine the effect of blossom and fruitlet thinners on crop load, fruit weight, seed development during the year of treatment, and the subsequent year effect on return bloom, fruit weight and yield, a field trial using the biennial apple cultivar `Northern Spy' (Malus × domestica Borkh.) was established. Treatments applied at full bloom included ATS (ammonium thiosulphate) [12% (w/v) nitrogen, 26% (w/v) S]; TD [15.9% (w/v) diacarboxylic acid, 5.5% (w/v) dimethylalkylamine salt (Endothal)] and SCY [57% (w/v) pelargonic acid (Scythe)]. At 18 days after full bloom (DAFB), oil treatments [98% (w/v) mineral oil (Superior “70” oil)] were applied with S [480 g·L-1 a.i. carbaryl (Sevin XLR)] and without as a means of increasing the efficacy of S. BA [19 g·L-1 a.i. 6-benzyladenine/1.9 g·L-1 a.i. gibberellins 4+7 (Accel)]; S; and/or SA [100% (w/w) 2-hydroxybenzoic acid (salicylic acid)], were also applied in a factorial arrangement on the same day. Fruit abscission was significantly increased the year of treatment with BA, S, BA + S, BA + SA, S + SA, BA + S + SA, oil, and S + oil. Average fruit weight was enhanced by S, BA + S, BA + SA, S + SA, BA + S + SA, and S + oil although in the latter treatment the crop load was very low. Only treatments that included BA reduced the number of fully developed seeds per fruit and seed number per trunk cross-sectional area (TCA) and increased return bloom. Defining the number of fully developed seeds per tree coupled with crop load is proposed as a predictor of return bloom in `Northern Spy'.

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Native Variation in Bloom and Crop Density in Spur-type `Delicious' and Effect of Ethephon Applied in High Crop Years

HortScience ◽

10.21273/hortsci.40.4.1096d ◽

2005 ◽

Vol 40 (4) ◽

pp. 1096D-1097

Author(s):

Martin J. Bukovac ◽

Jerry Hull ◽

Paolo Sabbatini

Keyword(s):

Apple Tree ◽

Cultural Practices ◽

Total Yield ◽

Fruit Size ◽

Alternate Bearing ◽

Full Bloom ◽

Crop Load ◽

Fruit Thinning ◽

Crop Density ◽

Return Bloom

For studies on blossom/fruit thinning in apple, tree selection is often based on uniformity of bloom/crop load, assuming that such trees exhibit greater uniformity to treatment. However, the literature is replete with data showing marked variation for a given treatment. We followed variation in bloom/crop density of spur-type `Delicious'/MM.106 and effect of ethephon applied in high crop years on return bloom/yield. Uniform trees (n = 95), under identical cultural practices, were selected for varying crop load. Return bloom, yield and fruit size were monitored over six years. General mean (X) for yield was 94 ± 25 kg/tree and bloom density, rated 1 to 10 (highest), was 5.4 ± 1.7. Annual yield deviated from X by +56 to –40% and bloom density by +49 to –42%. All trees were ranked (decreasing yield) and assigned to five percentile (PCTL) groups (1st, 81-100; 2nd, 61-80; 3rd, 41-60; 4th, 21-40; 5th, 0-20 kg/tree). Trees in each group were reassigned annually to the five PCPL groups for the next five years. Of trees in 1st PCTL (n = 19, X = 187 ± 10 kg/tree) in year one, 5, 5, 24, 0 and 63% placed in PCPL 1, 2, 3, 4, and 5, respectively, in year two. Of trees in 1st PCTL (5%) in year two, all placed in PCTL 2 in year three. Effect of ethephon [200 mg·L-1 at 3, 3 + 6, 3 + 6 + 9 weeks after full bloom (WAFB)] applied in on years to `Redchief', with strong alternate bearing, were evaluated for six years. Ethephon at 3 WAFB had no effect. Yield from multiple applications differed from control (NTC) in off years, but not from each other. Total yield (3 on + 3 off years) for the NTC and ethephon at 3 + 6 WAFB was similar (479 vs. 471 kg/tree). However, 64% of the total yield was produced in the on years and 36% in the off years in NTC vs. 56 and 44% in 3 + 6 WAFB, respectively.

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Effects of Prohexadione-Calcium on Fruit Size and Return Bloom in Pear

HortScience ◽

10.21273/hortsci.39.6.1305 ◽

2004 ◽

Vol 39 (6) ◽

pp. 1305-1308 ◽

Cited By ~ 8

Author(s):

David Sugar ◽

Don C. Elfving ◽

Eugene A. Mielke

Keyword(s):

Shoot Growth ◽

Fruit Size ◽

Fruit Weight ◽

Single Application ◽

Pear Fruit ◽

Crop Load ◽

Return Bloom ◽

Old Trees ◽

Prohexadione Calcium

The effects of prohexadione-calcium (P-Ca) on fruit size and return bloom in three pear cultivars were evaluated in Medford and Hood River, Ore., and in Cashmere, Wash. A variety of treatment dosages and timings was applied to 4- and 5-year-old trees in 2 years of study. Fruit weight of `Bosc' and `Red Anjou' pears was not affected by P-Ca treatments at any location in either year. However, decreased weight of `Bartlett' pear fruit was associated with all P-Ca treatments in 1999 in Medford except for 83 ppm applied at 2.5 to 6.0 cm shoot growth (first treatment) plus 2, 4, 6, and 8 weeks after first treatment (WAFT) and 125 ppm applied at 2.5 to 6.0 cm growth plus 4 WAFT. `Bartlett' fruit weight was reduced in Medford in 2000 by all treatments except 125 ppm applied at 2.5 to 6.0 cm growth plus 4, 8, and 12 WAFT. In Cashmere in 2000, mean weight of `Bartlett' and `d'Anjou' fruit was reduced by treatments with 83 or 125 ppm applied at 2.5 to 6.0 cm growth plus 2, 4, and 6 WAFT and of `Bosc' pear by all treatments that included more than a single application of P-Ca. Crop load was not significantly different among treatments at any location. Return bloom in the year following P-Ca treatment was reduced in `Bosc' pears by some to most treatments at all locations in both years. In contrast, return bloom was reduced in `Bartlett' and `Anjou' pears only in Hood River in 1999.

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Bio-regulators improve fruit size and c olour and reduce crop-load and annual bearing of Honeycrisp™ apples

Canadian Journal of Plant Science ◽

10.4141/p04-059 ◽

2005 ◽

Vol 85 (2) ◽

pp. 453-455

Author(s):

C. G. Embree ◽

D. S. Nichols

Keyword(s):

Fruit Quality ◽

Malus Domestica ◽

Fruit Size ◽

Fruit Weight ◽

Fruit Colour ◽

Full Bloom ◽

Crop Load ◽

Fruit Thinning ◽

Colour Category ◽

Return Bloom

Honeycrisp™ [Malus × domestica (L.) Borkh.] can be a very profitable cultivar if fruit quality is high. Some crop-load bio-regulators were evaluated for improving fruit quality and annual flowering. Ammonium thiosulphate applied at full bloom reduced crop-load, increased fruit weight, fruit colour and return bloom. Fruitone N® combined with Sevin XLR® reduced the percent of fruit in the 40–60% colour category and also crop-load. Fruitone N® alone reduced crop-load. Key words: Honeycrisp™, fruit thinning, crop-load, return bloom

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Influence of Mechanical String Thinning Treatments on Vegetative and Reproductive Tissues, Fruit Set, Yield, and Fruit Quality of ‘Gala’ Apple

HortScience ◽

10.21273/hortsci.48.1.40 ◽

2013 ◽

Vol 48 (1) ◽

pp. 40-46 ◽

Cited By ~ 10

Author(s):

Thomas M. Kon ◽

James R. Schupp ◽

H. Edwin Winzeler ◽

Richard P. Marini

Keyword(s):

Leaf Area ◽

Fruit Set ◽

Fruit Size ◽

Fruit Weight ◽

Spindle Speed ◽

State University ◽

Cross Sectional ◽

Spindle Rotation ◽

Return Bloom ◽

Extension Center

The objectives of this experiment were to test the efficacy of a mechanical string thinner (Darwin PT-250; Fruit-Tec, Deggenhauserertal, Germany) on apple and to identify an optimal range of thinning severity as influenced by spindle rotation speed. Trials were conducted in 2010 and 2011 at the Pennsylvania State University Fruit Research and Extension Center in Biglerville, PA, on five-year-old ‘Buckeye Gala’/M.9 apple trees that were trained to tall spindle. A preliminary trail on five-year-old ‘Cripps Pink’/M.9 was conducted to determine the relationship between string number and thinning severity. As the number of strings increased, the level of thinning severity increased. A range of spindle speeds (0 to 300 rpm) was applied to the same trees for two consecutive years. As spindle speed increased, blossom density (blossom clusters per limb cross-sectional area) was reduced as was the number of blossoms per spur. In 2010, leaf area per spur was reduced 9% to 45%. In 2011, the fastest spindle speed reduced leaf area per spur 20%. Although increased spindle speed reduced cropload, injury to spur leaves may have inhibited increases in fruit size. The largest gain in fruit weight was 28 g (300 rpm) compared with the control. In both years, the most severe thinning treatments reduced yield by more than 50%. There was no relationship between spindle speed and return bloom. Severe thinning treatments (240 to 300 rpm) caused significant reductions in spur leaf area, yield, and fruit calcium and did not improve fruit size or return bloom. Spindle speeds of 180 and 210 rpm provided the best overall thinning response and minimized injury to spur leaves, but cropload reduction was insufficient in years of heavy fruit set. Therefore, mechanical blossom thinning treatments should be supplemented with other thinning methods. Mechanical string thinning may be a viable treatment in organic apple production, where use of chemical thinners is limited.

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