scholarly journals Optimizing Continuous Canopy Shakers for Late Season `Valenica' Harvest

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 885A-885
Author(s):  
Richard S. Buker* ◽  
Jackie K. Burns ◽  
Fritz M. Roka
Keyword(s):  
Operating Conditions ◽  
Tree Size ◽  
Mature Fruit ◽  
Fruit Removal ◽  
Crop Load ◽  
Immature Fruit ◽  
Late Season ◽  
Southern Site ◽  
Mechanical Harvester

Continuous canopy shakers (CCS) were developed in the late 90's and have been used to commercially harvest citrus in Florida. A viable mechanical harvester in Florida must be able to selectively remove mature `Valencia' fruit. A study was conducted to evaluate the effect of operating conditions on mature and immature fruit removal during the 2003 harvest season. The study was conducted in the southern flat woods and northern ridge areas. The study treatments were completely random and replicated four times. The CCS treatments were 145, 215, 230, and 245 cycles per minute (cpm) and a hand picked control. The harvest occurred on 17 and 19 June at the southern and northern sites, respectively. Mature fruit removal linearly increased from 95.7% to 97.9% between 145 and 245 cpm, respectively. Varying the operating ranges significantly influenced mature fruit removal in the southern flat woods site. The trees at the southern site were taller (>4m), and had a larger crop load. At the northern ridge site where trees were smaller, varying the CCS operating ranges did not significantly influence mature fruit removal. Immature fruit removal was influenced by the operating ranges. Immature fruit removal was increased at least 22% over hand picked controls. The results were interpreted to indicate the frequency of CCS is dependent on tree size. The initial selectivity of the CCS was not equal to hand picking.

scholarly journals Late-season `Valencia' Orange Mechanical Harvesting with an Abscission Agent and Low-frequency Harvesting

HortScience ◽  
2006 ◽  
Vol 41 (3) ◽  
pp. 660-663 ◽  
Author(s):  
Jacqueline K. Burns ◽  
Fritz M. Roka ◽  
Kuo-Tan Li ◽  
Luis Pozo ◽  
Richard S. Buker
Keyword(s):  
Citrus Sinensis ◽  
Low Frequency ◽  
Mature Fruit ◽  
Fruit Removal ◽  
Immature Fruit ◽  
Late Season ◽  
Valencia Orange ◽  
Significant Difference ◽  
Orange Trees

An abscission agent (5-chloro-3-methyl-4-nitro-1H-pyrazole [CMNP]) at 300 mg·L–1 in a volume of 2810 L·ha–1 was applied to Valencia orange trees [Citrus sinensis (L.) Osb.] on 22 May 2004. At this time, immature and mature fruit were present on the tree simultaneously. Three days after application, fruit were mechanically harvested using a trunk-shake-and-catch system. The power to the shaker head was operated at full- or half-throttle (FT or HT, respectively), and the duration of trunk shaking was 2 seconds at FT or 4 seconds at FT and HT. Mature fruit removal percentage and number of immature fruit removed, and fruitlet weight and diameter were determined. Mature fruit removal percentage with 2 seconds at FT or 4 seconds at FT harvesting ±CMNP, or 4 seconds at HT + CMNP was not significantly different and ranged between 89% to 97%. Harvesting at 4 seconds HT without CMNP removed significantly less mature fruit than any treatment. CMNP did not affect immature fruit removal by the trunk shaker. Harvesting at 4 seconds at HT removed significantly less immature fruit than 2 seconds at FT or 4 seconds at FT. No significant difference in fruitlet weight or diameter was measured between any trunk shaker harvest operation and CMNP treatment. Trunk shaking frequency was estimated to be 4.8 and 8.0 Hz at HT and FT, respectively. Yield in 2005 was determined on the same trees used for harvest treatments in 2004. CMNP did not impact yield. No significant difference in yield was seen between the hand-picked control and 4 seconds at HT, whereas yield in the remaining treatments was lower. The results demonstrate that CMNP application combined with low frequency trunk shaker harvesting can achieve high percentage of mature fruit removal with no significant impact on return yield of the following crop.

scholarly journals Predicted Crop Value for Nectarines and Cling Peaches of Different Harvest Season as a Function of Crop Load

HortScience ◽  
2007 ◽  
Vol 42 (2) ◽  
pp. 239-245 ◽  
Author(s):  
Gabino H. Reginato ◽  
Víctor García de Cortázar ◽  
Terence L. Robinson
Keyword(s):  
Size Distribution ◽  
Field Experiments ◽  
Fruit Size ◽  
Tree Size ◽  
Crop Load ◽  
Early Season ◽  
Yield Efficiency ◽  
Late Season ◽  
Wide Range ◽  
Fruit Load

Several field experiments to assess the effect of tree size and crop load on fruit size and yield efficiency were conducted in cling peach and nectarine orchards of different harvest seasons in Chile. Trees were randomly selected in each orchard and then hand-thinned at the beginning of pit hardening to a wide range of crop loads. The fraction of above-canopy photosynthetically active radiation (PAR) intercepted by the canopy (PAR i) was determined at harvest. All fruits were counted and weighed and average fruit weight calculated. Crop load and yield were normalized by tree size measured by intercepted PAR i. For each orchard, the relationship between crop load and fruit size or crop load and yield efficiency was assessed by regression analysis. Fruit size distribution was calculated from fruit size adjusted for fruit load assuming a normal fruit size distribution and valued according to shipment date and price obtained from a Chilean export company. Using crop load as a covariate, fruit size adjusted for crop load was compared for nectarine and peach cultivars. Fruit size adjusted for fruit load and yield efficiency was greater with late season cultivars than the early or midseason cultivars. Predicted crop value (PCV), normalized in terms of PAR intercepted, was calculated for all the cultivars. Large differences in predicted crop value were found for early, midseason, and late ripening nectarines. Early and late ripening cultivars had the highest predicted crop value, especially at lower crop loads and larger fruit sizes. The early season cultivars had high crop value as a result of higher fruit prices, whereas the late season cultivar had high crop value as a result of higher production. With cling peaches, the early season cultivar ‘Jungerman’ had a lower predicted crop value than the late season cultivars ‘Ross’ and ‘Davis’. For cling peaches, the highest PCV was achieved at a relatively high crop load with high yield and small fruit size.

Effect of time of harvest on alternate cropping yields and fruit quality of Valencia orange trees

1978 ◽  
Vol 18 (92) ◽  
pp. 461 ◽  
Author(s):  
PT Gallasch
Keyword(s):  
Fruit Quality ◽  
South Australia ◽  
Mature Fruit ◽  
Late Season ◽  
Valencia Orange ◽  
The Common ◽  
Orange Trees ◽  
Early Harvest ◽  
Time Of Harvest

At Loxton, South Australia, early harvest of heavy, and late harvest of light, Valencia orange crops was compared with the common practice: early harvest of light and late harvest of heavy crops. These treatments were compared with two years of early, mid- or late season harvests. Early harvest of heavy and late harvest of light crops changed the 3.1:1.0 alternate cropping cycle to 1.1:10 and increased the light crop by 101 per cent compared with the common district practice which gave a 3.2 : 10 cycle. Consistent early and mid-season harvests reduced the alternate cropping ratio to 1.3 : 1.0 and 1.4 : 1.0 respectively, produced 14 per cent more fruit than the common district practice and avoided harvesting the light crop late, when fruit quality is poor. Mature fruit weights from trees consistently harvested late were 27 per cent lower than those trees harvested mid-season.

scholarly journals Severity of Scab and its Effects on Fruit Weight in Mechanically Hedge-Pruned and Topped Pecan Trees

Plant Disease ◽  
2017 ◽  
Vol 101 (5) ◽  
pp. 785-793 ◽  
Author(s):  
Clive H. Bock ◽  
Michael W. Hotchkiss ◽  
Tim B. Brenneman ◽  
Katherine L. Stevenson ◽  
William D. Goff ◽  
...  
Keyword(s):  
United States ◽  
Shoot Growth ◽  
Southeastern United States ◽  
Fruit Weight ◽  
Tree Size ◽  
Mature Fruit ◽  
Air Blast ◽  
Sample Height ◽  
Tree Canopies

Scab is the most damaging disease of pecan in the southeastern United States. Pecan trees can attain 44 m in height, so managing disease in the upper canopy is a problem. Fungicide is ordinarily applied using ground-based air-blast sprayers. Although mechanical hedge-pruning and topping of pecan is done for several reasons, improved management of scab is an important reason in the humid, wet Southeast. Resulting shoot growth on cut limbs of susceptible cultivars could lead to more severe scab. In three experiments over three years, we explored the effect of hedge-pruning trees to ∼12 to 14 m compared with non-hedge-pruned trees. All trees received fungicide treatments (air-blast sprays and ≤3 aerial applications). Hedge-pruning either had no effect, or increased or decreased scab severity only slightly on leaflets, immature, or mature fruit (a –9.95 to +14.63% difference in scab severity compared with the control). However, height in the canopy invariably had a large and significant effect on scab severity, and amounted to a 0.05 to 73.77% difference in severity between the lowest and highest sample in the canopy. Fruit weight depended on sample height, with fruit most often weighing less when collected at greater sample heights. A robust relationship between fruit weight and scab severity was found at the highest sample heights where scab was also most often severe (R2 = 0.21 to 0.67, P < 0.0001). Hedge-pruning and topping pecan tree canopies to manage tree size will enable better fungicide coverage, reducing risk of a scab epidemic as more of the canopy is assured efficacious fungicide spray coverage.

scholarly journals Modification of Carbohydrate Content in Developing Tomato Fruit

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 551E-551
Author(s):  
Arthur A. Schaffer ◽  
Marina Petreikov ◽  
Daphne Miron ◽  
Miriam Fogelman ◽  
Moshe Spiegelman ◽  
...  
Keyword(s):  
Carbohydrate Metabolism ◽  
Metabolic Pathways ◽  
Tomato Fruit ◽  
Starch Synthesis ◽  
Mature Fruit ◽  
Immature Fruit ◽  
Natural Genetic Variation ◽  
Structural Carbohydrate ◽  
Source Sink ◽  
The Impact

The carbohydrate economy of developing tomato fruit is determined by wholeplant source–sink relationships. However, the fate of the imported photoassimilate partitioned to the fruit sink is controlled by the carbohydrate metabolism of the fruit tissue. Within the Lycopersicon spp. there exists a broad range of genetic variability for fruit carbohydrate metabolism, such as sucrose accumulation and modified ratios of fructose to glucose in the mature fruit and increased starch synthesis in the immature fruit. Metabolic pathways of carbohydrate metabolism in tomatoes, as well as natural genetic variation in the metabolic pathways, will be described. The impact of sink carbohydrate metabolism on fruit non-structural carbohydrate economy will be discussed.

scholarly journals (463) Grapefruit Crop Load Affects Net Gas Exchange of Leaves, Tree Growth, and Fruit Quality

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1048A-1048
Author(s):  
Kuo-Tan Li ◽  
Jim Syvertsen ◽  
Jill Dunlop
Keyword(s):  
Fruit Quality ◽  
Fruit Size ◽  
Dry Weight ◽  
Fruit Shape ◽  
Solid Content ◽  
Soluble Solid Content ◽  
Citrus Paradisi ◽  
Fruit Removal ◽  
Crop Load ◽  
Four Levels

Effects of crop load on leaf characteristics, shoot growth, fruit shape, fruit quality, and return bloom were investigated in 13-year-old `Ruby Red' grapefruit (Citrus paradisi Macf.) on `Swingle' citrumleo rootstock. Trees were hand thinned in June 2003 and 2004 at the end of physiological fruit drop to establish three to four levels of crop load ranging from normal (high crop load without thinning) to extremely low (near 90% fruit removal). Leaves on high crop load trees had higher net assimilation of CO2 (ACO2) than those on low crop load trees. Crop load enhancement of ACO2 continued until harvest. In 2004, however, the effects were diminished in October just prior to the beginning of the harvest season, after leaf and fruit loss from three consecutive hurricanes. There was no difference in leaf dry weight per leaf area and leaf nitrogen among treatments. Nonfruiting branches of high crop load trees produced fewer, but longer, summer flushes than those of low crop load trees. Fruiting branches generally produced few summer flushes with similar shoot lengths among treatments. High crop load trees developed a greater percentage of vegetative shoots, whereas low crop load trees developed more inflorescences. Crop load adjustments did not affect fruit size and total soluble solid content, but low crop load trees produced a higher percentage of irregular shape (sheepnosed) fruit with high acidity.

scholarly journals Association between Fruit Development and Mature Fruit Drop in Huanglongbing-affected Sweet Orange

HortScience ◽  
2020 ◽  
Vol 55 (6) ◽  
pp. 851-857
Author(s):  
Lisa Tang ◽  
Sukhdeep Singh ◽  
Tripti Vashisth
Keyword(s):  
Fruit Development ◽  
Sweet Orange ◽  
Water Status ◽  
Fruit Size ◽  
Substantial Reduction ◽  
Fruit Growth ◽  
Mature Fruit ◽  
Callose Deposition ◽  
Immature Fruit ◽  
Fruit Drop

In the past decade, FL citrus industry has been struck by Huanglongbing (HLB), a disease caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas). Besides tree decline, HLB causes a sharp increase in mature fruit drop before harvest, leading to a substantial reduction in citrus production. The aim of the study was to provide insights in HLB-associated mature fruit drop. For HLB-affected ‘Valencia’ and ‘Hamlin’ sweet orange (Citrus sinensis), trees exhibiting severe symptoms (“severe trees”) had a significantly higher rate of mature fruit drop compared with mildly symptomatic ones (“mild trees”). Interestingly, dropped fruit were smaller than those still attached to tree branches regardless of the symptom levels of trees; overall, fruit of severe trees were smaller than mild trees. The result suggests a negative effect of HLB on fruit growth that may lead to a high incidence to drop subsequently at maturity. This possibility is further supported by the difference in immature fruit size as early as 2 months after bloom between severe and mild trees. Although HLB-triggered phloem plugging due to callose deposition in citrus leaves, which results in disrupted carbohydrate transport, has been documented in literature, the results of the histological analysis demonstrated no consistent pattern of callose deposition in the mature fruit pedicel in relation to the drop incidence. Additionally, sugar concentration in juice was not significantly different between dropped and attached fruit, providing evidence that carbohydrate shortage is not the case for dropped fruit and thus not the predominant cause of HLB-associated mature fruit drop. Notably, the midday water potential was significantly lower for severe than mild trees during the preharvest period (2 weeks before harvest of the current crop) in late March, which was also the second week after full bloom of return flowering. This suggests that altered tree water status due to HLB might limit fruit growth during the initial stage of fruit development (immediately after flowering) and/or increase the incidence of mature fruit abscission, leading to elevated preharvest fruit drop. Together, the results suggest that in the presence of HLB, strategies to increase fruit size and minimize additional stresses (especially drought) for the trees may improve mature fruit retention.

Abscission chemicals for Valencia oranges in New South Wales

1976 ◽  
Vol 16 (83) ◽  
pp. 943 ◽  
Author(s):  
B Freeman ◽  
RA Sarooshi
Keyword(s):  
No Reduction ◽  
New South ◽  
New South Wales ◽  
Mature Fruit ◽  
Fruit Removal ◽  
Visible Injury ◽  
Commercial Practice ◽  
South Wales ◽  
Leaf Drop ◽  
Horticultural Research

Three abscission chemicals inducing production of ethylene, have been evaluated as aids for mechanical harvesting of Valencia oranges at Horticultural Research Stations at Gosford (coastal) and Dareton (inland) in New South Wales during 1971-75. Ethephon (CEPA) promoted abscission without visible injury to the fruit but leaf drop at concentrations required to give adequate loosening (500 p.p.m.) was excessive. Cycloheximide (CHI) at 20 p.p.m. reduced fruit removal force (FRF) to 3.2 kg at Gosford and to 4.6 kg at Dareton in 1971, and again to 3.7 kg at Gosford in 1972. There was no reduction in FRF at Dareton in 1972. The addition of Polycote (R) (polyethylene emulsion) to CHI at Gosford enhanced theabscission response by reducing FRF an additional 20 per cent. Spraying before or after irrigation at Dareton; or during December, January or February at Gosford had no effect on FRF. Leaf and fruitelt drop caused by CHI were too high for commercial practice. Release (R) (CMNP) was selective for mature fruit only, and at concentrations up to 300 p.p.m. no fruitlet or leaf drop occurred while FRF was reduced to between 2 kg and 4 kg. This chemical was the most promising for incorporation into a mechanical harvesting system, but because of damage to the rind is limited to fruit for processing only.

Fruit Removal and Continual Defoliation Altered Papaya Fruit Production and Quality

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 497e-497
Author(s):  
Lili Zhou ◽  
David Christopher ◽  
Robert E. Paull
Keyword(s):  
Fruit Set ◽  
Sugar Content ◽  
Fruit Size ◽  
Sugar Accumulation ◽  
Sink Strength ◽  
Mature Fruit ◽  
Fruit Removal ◽  
Control Fruit ◽  
Significant Difference ◽  
Fruit Mass

The source size and sink strength were modified by continual defoliation and fruit removal in `Sunset' papaya. Flower and fruit set, mature fruit mass, and TSS was recorded weekly. Fruit at four different stages of development were harvested at the end of the experiment. Fruit mass, respiration, sugar content, and sucrose phosphate synthase (SPS), sucrose synthase (SS), and invertase enzyme activities were compared. Continual defoliation resulted in lower new fruit set (25% of control), smaller fruit size (77% of control), and lower TSS (85% of control) in the 24-week experimental period. In contrast, there were 52% and 100% more new fruit when fruit were removed than in the control within the first 8 weeks and 24 weeks, respectively. Larger fruit size, earlier fruit development, lower respiration, and higher sugar contents were observed when fruit were removed at 140, 154, and 175 days from anthesis. No significant difference was found in TSS level in the mature fruit compared to the control. Fruit removal plus defoliation gave the same number and mass of new fruit as the control and slightly lower TSS in mature fruit than in the control. Fruit sugar was higher with increased fruit invertase activity and fruit age. Data confirmed that source–sink balance was critical for fruit set, development, and sugar accumulation in papaya.

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