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

Burns, J. C.; Roka, Fritz; Li, Kuo‐Tan; Pozo, Luis; Buker, Richard S.

doi:10.21273/hortsci.41.3.660

Cited by 21 publications

(18 citation statements)

References 6 publications

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“…They found 2.5-fold increase in harvest debris by mechanical compared with hand-harvesting. Our study and others plus commercial experience have shown that with healthy well-managed trees, mechanically harvesting trees does not reduce yield or tree health (Burns et al, 2006;Melgar et al, 2010). However, the present study is the first to indicate that the interaction of water stress and canopy density did not negatively impact leaf area density or yield.…”

Section: Discussioncontrasting

confidence: 43%

“…Recovery rates in fruit from mechanically harvested trees are typically 80% to 95% with abscission agents (Burns et al, 2006;Ebel et al, 2012). Less aggressive canopy shaking without abscission agents to reduce damage to the trees resulted in increased cost of handharvesting fruit remaining in the trees after mechanical harvesting.…”

Section: Resultsmentioning

confidence: 99%

“…Previous experiments on the effect of mechanical harvesting with trunk shakers (Burns et al, 2006; and canopy shakers (Ebel et al, 2012) found little effect on citrus tree health that reduced long-term yield when they were conducted on well-watered trees with high canopy densities. Burns et al (2006) did find that trees treated with an abscission agent [5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP)] and harvested with a trunk shaker at low speed and handharvesting did not reduce yield the next year. However, the use of CMNP and trunk shakers at high speed was found to reduce followingyear yields in the same study.…”

mentioning

confidence: 94%

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Effects of Short-term Drought Stress and Mechanical Harvesting on Sweet Orange Tree Health, Water Uptake, and Yield

Morgan

Barkataky

Kadyampakeni

et al. 2014

horts

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One of the primary reasons for the slow adoption of mechanical harvesting by Florida citrus growers is the physical injuries associated with it, including loss of leaves, twigs, flowers, and young fruits, limb breakage, and injuries to the bark and root. However, it has been shown that well-managed trees are capable of tolerating defoliation, limb loss, and root and bark injury caused by mechanical harvesting. Irrigation management is one of the most crucial factors that influence citrus tree health. A multiple-year field study was conducted on ‘Valencia’ sweet orange trees in a commercial citrus grove near Immokalee, FL, to determine the effect of initial tree canopy density and short-term drought stress on tree health, water uptake, and productivity of mechanically harvested trees. Three blocks were based on canopy density and overall appearance and indicated as low, moderate, and high canopy density. The experiment was laid in a split-plot design with four replications of six-tree plots of hand-harvested or mechanically harvested trees, taking drought stress or full irrigation as main treatments. The experimental design was repeated with trees in each plot of one of the three canopy density categories. After harvest, each six-tree plot was split into two three-tree subplots, where one subplot was drought-stressed and the other was fully irrigated. Harvesting was conducted in the Spring of 2010, 2011, and 2012 with the same experimental design and data collection procedures. The effects of short-term drought on water use and stem water potential were masked by heavy rains in Spring 2010 and thus no differences in the irrigation treatments were observed. In 2011 and 2012, stem water potential was unaffected by harvesting method. Water use was unaffected by harvesting method across the 3 years. Drought stress significantly increased pull force required to remove fruit and stem water potential after harvest. Although mechanically harvested trees lost leaf mass, with no rain before harvest, results from Spring 2011 and 2012 indicated that short-term drought stress had no effect on citrus leaf area irrespective of harvest method. Drought stress significantly increased fruit detachment force in low and moderate density but not in high-density trees resulting in increased force required to remove fruit from trees with moderate- to low-density canopies. Yield increased from 2010 to 2011 for mechanically harvested trees compared with hand-harvested for low-canopy density trees by 17% and moderate-canopy density trees by 8%, whereas high-density plots indicated similar yield after mechanical harvesting. Comparatively, yield in 2012 decreased in the low and moderate densities compared with yield in 2011 but increased in the high density by 14% and 53% in hand- and machine-harvested trees, respectively. Despite finding 2- to 3-fold more debris in the mechanically harvested trees than the hand-harvested trees, yields and other measured parameters were unaffected suggesting that mechanical harvesting of citrus trees did not have an adverse effect on growth and production of well-watered citrus trees.

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Section: Discussioncontrasting

confidence: 43%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 94%

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Effects of Short-term Drought Stress and Mechanical Harvesting on Sweet Orange Tree Health, Water Uptake, and Yield

Morgan

Barkataky

Kadyampakeni

et al. 2014

horts

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“…At the onset of the cell elongation stage of fruitlet growth, certain growth regulators such as CMNP can be applied at concentrations that loosen mature fruit but not fruitlets, whereas ethephon will cause abscission in both (Burns, 2002). In this case, CMNP can be used to selectively loosen mature fruit without removing fruitlets, provided that machine harvesting is performed at reduced frequency (Burns et al, 2006). Developmental changes in sensitivity to abscise naturally or in response to growth regulator applications in fruit such as citrus have been described (Abeles et al, 1992;Brown, 1997;Guardiola and García-Luis, 2000).…”

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confidence: 99%

Organ Loss and Yield Impacts of ‘Valencia’ Sweet Orange in Response to Fruit Abscission Agents

Pozo¹,

Burns²

2009

horts

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To successfully use abscission agents for ‘Valencia’ sweet orange mechanical harvesting throughout the harvest season, unwanted flower, fruitlet, and leaf drop must be assessed and minimized. Ethephon (400 mg·L−1), 1-methylcyclopropene (1-MCP; 5 mm), ethephon + 1-MCP, 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP; 200 mg·L−1), and a kinetic adjuvant control [0.15% (v/v)] were applied to ‘Valencia’ branches at various times from full bloom in Mar. 2006 to the end of full bloom in Mar. 2008. Effects of these treatments on fruit detachment force (FDF) and abscission of developing and mature fruit, flowers, and leaves were recorded. Three separate response periods to abscission agent applications were observed: the first spanned the first 100 days after bloom (DAB) and was characterized by high initial response followed by decreasing sensitivity; the second spanned between 100 and 225 DAB and was characterized by little to no response; and the third spanned from 225 DAB to harvest and was characterized by a gain in sensitivity. Young fruitlets in the first response period were highly sensitive to ethephon but were less sensitive to CMNP or ethephon + 1-MCP. Mature fruit in the third response period were highly sensitive to CMNP and less sensitive to ethephon or ethephon + 1-MCP. The application of ethephon resulted in high leaf abscission and showed no clear sensitivity pattern throughout both cropping years. CMNP or ethephon + 1-MCP application caused minimal leaf abscission. The same abscission agent treatments were applied on whole tree canopies 6 and 28 DAB in Mar. 2007. Application date had no significant effect on the measured parameters. Although ethephon application induced high initial leaf drop, leaf area indices determined 7 months after any compound application were not significantly different. However, subsequent 2008 yield in trees sprayed with ethephon in 2007 was significantly less, whereas 2008 flower number was higher. The results indicate a complex interaction of fruitlet abscission and leaf loss during the first response period contributed to yield reduction and increased flower number in ethephon-treated trees.

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“…Reducing the intensity of the harvest machine to prevent green fruit removal during late season harvesting has shown to be impractical due to decreased efficiency of the harvesting operation. However, removal of mature and young green fruit could be differentiated by using fruit abscission compounds (Burns et al, 2006), provided the compounds are selective for mature fruit and nonphytotoxic.…”

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confidence: 99%

Recovery from Phytotoxicity after Foliar Application of Fruit-loosening Abscission Compounds to Citrus

Li¹,

Burns²,

Syvertsen³

2008

J. Amer. Soc. Hort. Sci.

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The use of abscission compounds to loosen fruit from stems can be accompanied with various levels of phytotoxicity. To determine the effects of a promising abscission compound, 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP), and ethephon on sweet orange [Citrus sinensis (L.) Osbeck] leaf function, water relations, and young fruit growth, we sprayed CMNP at 0, 200, 500, 1000, or 2000 mg·L−1 or ethephon at 400 or 800 mg·L−1 to fruiting branches of potted and field-grown sweet orange during the 2005–06 harvest season. Both compounds induced abscission of mature fruit and leaves 3 days after application but had little effect on leaf chlorophyll content, water content, and midday leaf water potential (Ψleaf) of remaining leaves. CMNP sprayed at 200 mg·L−1 or either concentration of ethephon did not affect leaf photosystem II efficiency, as indicated by leaf chlorophyll fluorescence (Fv/Fm). High CMNP concentrations (1000 or 2000 mg·L−1) reduced Fv/Fm 1 day after treatment, but Fv/Fm of leaves remaining on sprayed branches gradually recovered to the level of control leaves by 4 days after treatment. Similarly, high concentrations of CMNP and ethephon temporarily reduced net gas exchange of leaves for about 4 days. Young fruit growth also was temporarily inhibited by CMNP concentrations greater than 200 mg·L−1. We conclude that CMNP sprayed at recommended concentrations (200–500 mg·L−1) caused mature fruit abscission with little long-term phytotoxic effect on leaves or young fruit.

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

Cited by 21 publications

References 6 publications

Effects of Short-term Drought Stress and Mechanical Harvesting on Sweet Orange Tree Health, Water Uptake, and Yield

Effects of Short-term Drought Stress and Mechanical Harvesting on Sweet Orange Tree Health, Water Uptake, and Yield

Organ Loss and Yield Impacts of ‘Valencia’ Sweet Orange in Response to Fruit Abscission Agents

Recovery from Phytotoxicity after Foliar Application of Fruit-loosening Abscission Compounds to Citrus

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