297 EFFECTS OF NAA ON FRUIT SIZE OF `DELICIOUS' APPLES

Post-bloom fruit thinning of spur-type `Delicious' with NAA may occasionally result in excessive small fruit (50 - 67 mm) not correlated with crop load. We evaluated the effect of carrier volume and time of application on incidence of small fruit over three growing seasons. A constant dose of NAA (30 g·ha-1) was applied in 230 to 2100 liter·ha-1 at about 10 mm king fruit diameter (KFD). Amount of NAA-induced small fruit differed from year to year, but there was no significant effect of carrier volume in any given year. NAA (15 mg·liter-1) was applied as a dilute spray at 5 to 22 mm KFD. Time of application influenced fruit size distribution at harvest in only one of three years. The incidence of small fruit appeared more closely related to temperature during spray application than to carrier volume or time of application. The effect of NAA on growth rate of king fruit with minimal competition (branches hand thinned, no lateral fruit) was determined over the first month after thinning. There was no pronounced effect of NAA on post-treatment growth rate. In a related study, NAA caused a significant decrease in fruit size when two or more fruit were competing on the same spur, while fruit size in the absence of intra-spur competition was not significantly reduced.

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Interaction of NAA with Accel and Promalin on Fruit Size in `Delicious' and `Empire' Apples

HortScience ◽

10.21273/hortsci.30.4.765c ◽

1995 ◽

Vol 30 (4) ◽

pp. 765C-765

Author(s):

Martin J. Bukovac ◽

Brent L. Black ◽

Jerome Hull

Keyword(s):

Strong Interaction ◽

Fruit Size ◽

Split Application ◽

Fruit Thinning ◽

Small Fruit ◽

Fruit Diameter

NAA and Accel are used for fruit thinning of apples. However, when combined, many small (<65 mm) fruit were produced in `Delicious'. We extended our studies using Redchief `Delicious' and `Empire', and, since BA is common to both Accel and Promalin, to study the effect of NAA-thinning sprays on Promalin-treated Redchief trees. NAA (10–15 mg·liter–1) and Accel (25–100 mg·liter–1) were applied to Redchief and `Empire' at 100-mm king fruit diameter (KFD). NAA interaction with Promalin was studied using Redchief. Promalin (1.5 pt/A) was applied as a single spray (80% king bloom, KB) and as a split application (0.75 pt/A, 80% KB and repeated at 10-mm KFD) with NAA (15 mg·liter–1) at 10-mm KFD. In `Delicious', 2% to 9% of the fruit from Accel-treated trees was <65 mm in diameter, compared to 11% for NAA alone. However, when NAA was applied with Accel, 22% to 30% of the fruit was <65 mm and percentage of large fruit (75 mm+) was reduced by 24% to 36%. There was no strong interaction for fruit size in `Empire', but the combination decreased yield. NAA applied to Promalin-treated `Delicious' increased percentage of small fruit dramatically (14% to 25%). No increase in small fruit was observed with Accel of Sevin.

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`Empire' Apple Responses to Fruit-thinning Chemicals

HortScience ◽

10.21273/hortsci.30.4.765e ◽

1995 ◽

Vol 30 (4) ◽

pp. 765E-765 ◽

Cited By ~ 1

Author(s):

Warren C. Stiles

Keyword(s):

Size Distribution ◽

Fruit Set ◽

Total Yield ◽

Fruit Size ◽

Diameter Ratio ◽

Time Of Application ◽

Fruit Thinning ◽

Small Fruit

Effects of NAA at 5, 10, and 15 ppm, Accel at 50, 75, and 100 ppm, NAA at 7.5 ppm plus carbaryl at 600 ppm, and a nontreated control on fruit set, fruit size, length–diameter ratio, seed numbers per fruit, and total yield of fruit were evaluated during the 1994 season. All treatments were applied to 10-year-old `Empire'/M.9/MM.111 trees as dilute sprays at a rate of 935 liters·ha–1 with an airblast sprayer on 3 June. King fruit measured 9–11 mm in diameter at time of application. Fruit set (fruits per 100 blossom clusters) was reduced significantly by Accel at 50 ppm (17%) and by NAA plus carbaryl (26%) in comparison with the nontreated control. Total yield of fruit was increased by all treatments; however, fruit from trees treated with NAA plus carbaryl was significantly larger than that from all other treatments. Percentages of small fruit, <108 g, were reduced by all treatments. Percentage of fruit ≥ 153 g was increased significantly only by NAA plus carbaryl. Length–diameter ratios and numbers of fully developed seeds per fruit were not influenced significantly by treatments. NAA at rates of 5, 10, and 15 ppm, or Accel at 50, 75, or 100 ppm, were less effective than a combination of NAA at 7.5 ppm plus carbaryl at 600 ppm in reducing fruit set and in affecting fruit size or fruit size distribution.

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Characterizing the Interaction between NAA and BA on Apple Fruit Abscission and Development

HortScience ◽

10.21273/hortsci.43.6.1794 ◽

2008 ◽

Vol 43 (6) ◽

pp. 1794-1801 ◽

Cited By ~ 3

Author(s):

Martin J. Bukovac ◽

Paolo Sabbatini ◽

Philip G. Schwallier ◽

Michael Schroeder

Keyword(s):

Strong Interaction ◽

Fruit Size ◽

Apple Fruit ◽

Fruit Growth ◽

Crop Load ◽

Fruit Thinning ◽

Small Fruit ◽

Golden Delicious ◽

Fruit Formation ◽

Fruit Diameter

NAA and BA are important compounds for regulating crop load in apples (Malus domestica Borkh.). When used for fruit thinning, both induce abscission, but at an equivalent crop load NAA tends to reduce and BA to increase fruit size. There is a strong interaction between NAA and BA when used together on ‘Delicious’ and ‘Fuji’, leading to excessive development of pygmy and small fruit (<65 mm diameter). The combination of BA (as Promalin, 1:1 BA + GA4+7) applied at king bloom (KB) and NAAm (amide) at petal fall increased the percentage of small fruit by 3.3- or 5.1-fold compared with BA or NAAm alone. Similar results were obtained with BA (Promalin) at KB oversprayed with NAA at 10 to 12 mm king fruit diameter (KFD). When NAA was oversprayed with BA during fruitlet development, i.e., 5 to 6 mm, 10 to 12 mm, and ≈18 mm KFD, the greatest inhibition of fruit growth occurred at the 10- to 12-mm KFD stage, and there was no significant effect at 18 mm KFD. Inhibition by treatment at the 5- to 6-mm stage was intermediate and trees were overthinned. NAA + BA inhibition of fruit growth in ‘Delicious’ and ‘Fuji’ was not crop load-dependent. In all experiments, crop load (wt basis) of trees treated with NAA + BA was similar or less than of those treated with NAA or BA alone, but they produced 2.5- to 5-fold more small fruit. NAA + BA increased the number of fruit per cluster, many of which failed to fully develop. Increasing the ratio of BA to NAA from 25:15 to 125:15 mg·L−1 increased small fruit formation. The presence of GA4+7 in commercial formulations of BA (0:100, Maxcel; 10:100, Accel; 50:50, Promalin) did not significantly affect the NAA + BA response. Fruit growth was not inhibited by the NAA + BA combination in large-fruited ‘Golden Delicious’ and ‘Jonagold’ and was increased in small-fruited ‘Elstar’ and ‘Gala’ compared with the nontreated control.

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Temperature Has a Greater Effect on Fruit Growth than Defoliation or Fruit Thinning in Strawberries in the Subtropics

Agriculture ◽

10.3390/agriculture9060127 ◽

2019 ◽

Vol 9 (6) ◽

pp. 127

Author(s):

Christopher M. Menzel

Keyword(s):

Opposite Effect ◽

Fruit Size ◽

Fruit Weight ◽

Fruit Growth ◽

Effect Of Temperature ◽

Fragaria Ananassa ◽

Fruit Thinning ◽

Mature Leaves ◽

Small Fruit ◽

Marketable Fruit

Fruit size declines in strawberries (Fragaria × ananassa Duch.) as the season progresses in many subtropical areas, possibly due to inadequate leaf area, over-cropping, or high temperatures. An experiment was conducted to investigate the importance of these factors on fruit growth in ‘Festival’ in Queensland, Australia. Groups of plants were defoliated to remove half of the mature leaves on each plant, thinned to remove all the inflorescences on each plant, or defoliated and thinned. Control plants were left intact. Defoliation, thinning, or defoliation + thinning decreased yield (total and/or marketable) by 15% to 24% compared with the control. Defoliation, or defoliation + thinning decreased average fruit weight (total and/or marketable fruit) by 1 to 2 g compared with the control, whereas thinning had the opposite effect. The incidence of small fruit increased towards the end of the season. There were strong relationships between fruit weight and average daily mean temperature in the seven weeks before harvest (R2s greater than 0.80). Fruit weight decreased from 24 g to 8 g as the temperature increased from 16 °C to 20 °C. This response was not affected by defoliation or thinning. The strong effect of temperature on fruit size indicates a problem for production in the future in the absence of heat-tolerant cultivars.

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Thinning and Diametric Fruit Growth Response of Apple Trees Treated with Benzyladenine and GA4+7 (Accel®), Carbaryl, and NAA

HortScience ◽

10.21273/hortsci.30.4.787e ◽

1995 ◽

Vol 30 (4) ◽

pp. 787E-787

Author(s):

John A. Cline ◽

Mary Bom ◽

Donald C. Elfving

Keyword(s):

Growth Response ◽

Additional Data ◽

Fruit Size ◽

Fruit Growth ◽

Sharp Decline ◽

Fruit Thinning ◽

Growing Seasons ◽

Fruit Maturity ◽

Cluster Rate ◽

Number Of Seeds

A series of seven fruit thinning experiments with benzyladenine (BA), benzyladenine and GA4+7 (10:1 BA:GA4+7, Accel), carbaryl (CB), and NAA were conducted at the Horticultural Experiment Station, Simcoe, during the 1993 and 1994 growing seasons. In 1993, BA and Accel at 0, 100, 200, and 300 mg of BA/liter were applied to mature `Redspur Delicious'/M.26 and `Empire'/M.26 trees when fruit were ≈10 mm in diameter. In one set of experiments in 1994, Accel was applied at 0, 25, 50, 100, 150, and 200 mg of BA/liter to mature `McIntosh'/M.26 and `Empire'/M.7 trees. In a second set of experiments in 1994, Accel was applied at 0, 50, and 100 mg of BA/liter to mature `Idared'/M.26, `Empire'/M.26, and `Marshall McIntosh'/Mark trees when fruit were ≈10 mm in diameter. Additional treatments included bloom sprays of Accel at 50 mg of BA/liter, and sprays of BA at 50 mg a.i/liter, NAA at 10 mg a.i./liter, CB at 1000 mg a.i./liter, and a “low” (two fruit remaining/flower cluster) and `”high” (one fruit remaining/flower cluster) rate of hand thinning. In all experiments, thinning response to BA and Accel increased with concentration. Concentrations below 50, 100, and 300 mg BA/liter were generally ineffective for thinning `Empire', `Idared', and `McIntosh', and `Delicious', respectively. Fruit size of `Idared' and `Empire' was increased at rates of 50 mg BA/liter, whereas rates of 100 mg BA/liter were needed to increase fruit size of `McIntosh'. Accel applied to `Empire' at 150 mg BA/liter decreased the number of seeds per fruit and increased fruit length:diameter (L:D) ratios. Concentrations of Accel exceeding 100 mg BA/liter in `Red Delicious' decreased the number of seeds per fruit, while having little effect on fruit L:D ratios even though lower concentrations increased fruit L:D ratios. Diametric fruit growth measurements in 1994 indicated a temporary, but sharp, decline in growth rate immediately following treatment imposition for trees that responded positively to thinning. Additional data describing treatment effects on fruit size distribution, vegetative growth, and fruit maturity will be presented and discussed in relation to crop load.

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657 Relationship between Intensity of Flowering and Cropping in Fruit and Nuts

HortScience ◽

10.21273/hortsci.34.3.561c ◽

1999 ◽

Vol 34 (3) ◽

pp. 561C-561

Author(s):

E.W. Stover

Keyword(s):

Fruit Set ◽

Fruit Size ◽

Commercial Application ◽

Critical Periods ◽

Alternate Bearing ◽

Crop Species ◽

Fruit Thinning ◽

Small Fruit ◽

Substantial Investment ◽

Flowering Intensity

The relationship between intensity of flowering and various aspects of cropping will be reviewed for fruit and nuts. Clearly, relatively light flowering can limit yield in most fruit and nut species. This commonly occurs before mature bearing commences and in “off” years for varieties that display alternate bearing. During mature bearing, many species will carry fruit numbers that exceed commercially desired levels, resulting in excessively small fruit and accentuating alternate bearing. The economic disadvantages of excess cropload have resulted in considerable research on fruit thinning and widespread commercial application of this practice. Heavy flowering intensity in some crop species results in economic disadvantages beyond the problems of excessive cropload and resultant small fruit size. Many species flower profusely and have initial fruit set far in excess of final tree capacity, resulting in abscission of numerous flowers and fruitlets. Abscised organs can represent a substantial investment in carbohydrates and nutrients, compromising availability at critical periods in flower and fruit development. The potential implications of this process are best exemplified in navel orange, where an increase in flowering beyond intermediate intensity results in a reduction in both initial fruit set and final fruit yield at harvest. In several crops, there is evidence that fruit size may be reduced by excessive flowering, even when cropload is quickly adjusted to an acceptable level. These data suggest that further research on the advantages of controlling flowering intensity is warranted.

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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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Cropping and Fruit Growth in Redchief `Delicious': An Analysis of the Effect of NAA and Cytokinins

HortScience ◽

10.21273/hortsci.32.3.525a ◽

1997 ◽

Vol 32 (3) ◽

pp. 525A-525

Author(s):

Martin J. Bukovac ◽

John C. Neilsen ◽

Jerome Hull

Keyword(s):

Fruit Size ◽

High Volume ◽

Inhibitory Effect ◽

Tree Age ◽

Marked Variation ◽

Crop Load ◽

Fruit Thinning ◽

Single Tree ◽

Small Fruit ◽

Effect On Yield

Generally, NAA is effective in inducing fruit thinning in `Delicious'. Although significant thinning may be induced, fruit size at harvest may not be closely related to crop load. Further, the magnitude of response to NAA may vary markedly between seasons. Herein, we present an analysis of response of `Redchief Delicious' over several years (tree age 11–14 years old) to high-volume sprays of NAA (15 mg·L–1), BA (25-50 mg·L–1), and CPPU (5 mg·L–1) at KFD of 8–12 mm. A single tree was used for each treatment replicated four to six times and response was measured by yield and fruit size distribution for each tree. In eight experiments over 4 years, NAA resulted in an average 22% reduction in yield, a 5.1% reduction in large fruit (70 mm+) and 2% reduction in small (<64 mm) fruit compared to NTC. There was a marked variation in response among years. Over 4 years, BA averaged a 5% decrease in yield, a 15% increase in large fruit and a 21% decrease in small fruit. In contrast, when NAA was combined with BA at 25-50 mg·L–1, yield decreased an average of 30%, large fruit decreased by 68%, and small fruit increased 8-fold (2.54 vs 20.6 kg/tree). CPPU alone (2-year study) had no significant effect on yield, but increased large fruit by 60% and significantly reduced production of small fruit. When CPPU was combined with NAA, yield was reduced in both years and the amount of large fruit was increased in 1995, but decreased in 1996. NAA had a very inhibitory effect on fruit size in 1996. One explanation may be that the crop was produced by lateral fruit (king flowers were lost to frost), and NAA has a greater inhibitory effect on lateral than king fruit. Results will be discussed in relation to studies with `Jonathan' and `Empire'.

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Effect of Concentration and Time of Accel Application on Cropping of Selected Cultivars

HortScience ◽

10.21273/hortsci.30.4.765b ◽

1995 ◽

Vol 30 (4) ◽

pp. 765B-765 ◽

Cited By ~ 2

Author(s):

Jerome Hull ◽

Martin J. Bukovac ◽

Brent L. Black

Keyword(s):

Size Distribution ◽

Fruit Size ◽

High Volume ◽

Fruit Weight ◽

Yield Reduction ◽

Early Application ◽

Time Of Application ◽

Significant Yield ◽

Spray Volume ◽

Fruit Diameter

The effect of Accel concentration and time of application on fruit size and yield was studied using `Delicious' (Redchief), `Empire', `Jonathan', and `Gala'. High-volume sprays of Accel were applied at 25 to 150 mg·liter–1 to `Delicious' and `Empire' at king fruit diameter (KFD) of 5 to 20 mm. `Jonathan' and `Gala' were treated at KFD of 5 to 20 mm with 10 to 40 g/A. The effect of spray volume (500 to 2000 liters·ha–1) and surfactant (Regulaid) was studied using `Jonathan'. Response was indexed by yield and fruit size distribution at harvest. Although yield in `Delicious' was reduced with all concentrations of Accel, the percentage of fruits in the larger-size classes (3”+) was not significantly increased. In contrast, with `Empire', Accel reduced fruit load similar to hand-thinning (HT) and percentage of large fruit equaled or exceeded that of the HT treatment. Increasing concentration of Accel was related to an increase in fruit size; early application (5 mm KFD) was more effective than late (10, 20 mm KFD) application. There was no significant effect of spray volume or Regulaid. Increasing Accel rate (10 to 20 g/A) resulted in significant yield reduction and increase (4% to 9%) in mean fruit weight in `Gala'.

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Experience with Thinning: What Factors Contribute to Contradicting Results?

HortScience ◽

10.21273/hortsci.33.3.553e ◽

1998 ◽

Vol 33 (3) ◽

pp. 553e-553

Author(s):

Richard Marini

Keyword(s):

Fruit Size ◽

Multiple Regression Model ◽

Sampling Techniques ◽

Location Factors ◽

Fruit Thinning ◽

Factors Influencing ◽

Application Techniques ◽

Sources Of Variation ◽

Fruit Diameter ◽

Tree Condition

Results from chemical thinning trials often vary with location/researcher and from year to year within a location. Factors influencing both sources of variation will be discussed. For help explain seasonal variation, the effects of fruit size and temperature will be discussed. A multiple regression model was developed indicating that the degree of fruit thinning is influenced by the interaction of temperature two days after treatment and fruit diameter at the time of treatment. Factors contributing to contradicting results between experiments/researcher include application techniques, types of data collected, differences in experimental designs and sampling techniques, statistical analyses, and potential differences in the tree condition at the time of thinning applications.

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