Abscission Chemicals Research Articles

Experiments on the Mechanical Harvesting of Litchi and its Effects on Litchi Storage

Abstract. This article presents a fruiting branch shaker designed for litchi ( Sonn.) harvesting and field testing results of the mechanical shaker with abscission chemical treatment. During the mature litchi season, mechanical harvesting experiments were conducted on Feizixiao litchi trees with and without applying the abscission chemical (Ethrel, 2-chloroethyl phosphoric acid). Fruit detachment force (FDF) and fruit weight (W) were measured to determine the effect of chemical treatment on the FDF/W ratio. Fruits harvested by different methods were transported to the laboratory in Guangzhou city and stored at 6°C. Testing results showed that more than 88% of litchi fruits untreated with the chemical were removed at a frequency of 26 or 32 Hz and that the harvesting rate was roughly 3.5 times greater than that of hand harvesting. Application of the abscission chemical increased the removal percentage and harvesting rate of litchi fruits by about 10% while showing a decreased damage rate. Storage tests also indicated no significantly different characteristics between untreated fruits harvested by the shaker and by hand. However, there were significant differences between treated fruits and untreated fruit in browning index and total soluble solids content. Keywords: Abscission chemical, Detachment force, Litchi (Litchi chinensis Sonn.), Mechanical harvest, Multi-finger branch shaking.

Effect of harvesting with a trunk shaker and an abscission chemical on fruit detachment and defoliation of citrus grown under Mediterranean conditions

Spain ranks as the world’s leading exporter of citrus for fresh consumption. Manual harvest accounts for 50% of the total production costs. Mechanical harvest would increase labor productivity and benefits of growers. Efficiency of these machines depends on the varieties and operating conditions. Use of abscission chemicals has been promoted to increase the detachment rate of fruit without affecting its quality. This work is aimed at studying whether the mechanical harvest and/or the application of an abscission agent affect the quality and quantity of harvested fruit and tree defoliation under the conditions of citrus cultivation in Spain. Trials were made in a completely randomized experimental design. From 2008 to 2011, different orchards of mandarin and orange trees were sprayed with different doses of ethephon as abscission agent and harvested with a trunk shaker. Harvest related variables (detachment percentage, defoliation and fruit without calyx) were measured. The percentage of fruit detached by the trunk shaker ranged between 70 and 85% and it did not depend on the orchard. The shaker produced minimal damage to the bark when gripped incorrectly. Increased doses of ethephon increased fruit detachment except in ‘Clemenules’ orchard, but also increased the fruit without calyx in 1-9%. Moreover, ethephon promoted significant defoliation. Neither gummosis nor death of branches was observed. This work demonstrates that mechanical harvesting with trunk shakers may be a feasible solution for citrus cultivated in Spain for fresh market. Use of ethephon could only be recommended for citrus destined to industry and only for certain varieties.

Olive removal with pneumatic branch shaker and abscission chemical

This study involves designing a branch shaker operating with an air compressor and its application for harvesting olives. Fruit detachment force (FDF) and fruit weight ( W) were measured and hence the changes in the percentage of removed fruits with shaking were determined at different maturity times. During the harvesting season, two sets of experiments were conducted to test the shaker in the removal of Halhali cultivar olives ( Olea europaea L.) with and without application of abscission chemical (ethrel). Experiments were also carried out to determine the effect of the chemical on fruit detachment force, fruit weight, and mechanical harvesting efficiency. Shaking tests showed that the removal percentage of olives without chemical application was lower than 50%. However, application of abscission chemical reduced the FDF/ W ratio and thus increased the removal percentage of olives. The lowest fruit detachment force and the highest fruit removal (96%) were obtained by employing a frequency of 24 Hz and 12.5 mL/L concentration of abscission chemical with constant amplitude of 60 mm. Moreover, it was found that the fruit removal efficiency increases with decreasing olive detachment forces.

Effect of Application Techniques on Abscission Chemical Deposition and Mechanical Harvesting of `Valencia' Oranges

Field experiments were conducted to investigate the effect of sprayer type, airflow rate, and nozzle output on deposition of active ingredient and mechanical harvesting of `Valencia' orange (Citrus sinensis). Fruit detachment force (FDF) and percentage of fruit removal (PFR) by trunk shaker were used as mechanical harvesting parameters. A PowerBlast sprayer discharging radially and a Titan sprayer discharging over the entire canopy were used. The spray mixture contained an abscission chemical (CMN-pyrazole), a surfactant (Kinetic) and a fluorescent tracer (Pyranine-10G). Deposition was determined at three different heights outside and inside of the canopy. With the PowerBlast, higher airflow and lower nozzle output reduced deposition of the active ingredient. The mean FDF of sprayed treatments was less than that of the non-sprayed control but the difference among the four spray treatments was not significant. The lower airflow rate with lower nozzle output had higher PFR than that of the control. With the Titan sprayer, the mean deposition at lower airflow was similar to or higher than the higher airflow. At higher airflow, the lower nozzle output gave higher mean deposition. The Titan sprayer treatments resulted in less FDF than the control. At both airflow rates, the FDF was less at lower nozzle output than at higher nozzle output. The PFR of these treatments were not different from that of control.

Naphthalene Acetic Acid and 2,3,5-triiodobenzoic Acid Affect the Response of Mature Orange Fruit to Abscission Chemicals

Effects of NAA, TIBA, ethephon, and CMN-Pyrazole on fruit detachment force (FDF) of mature `Valencia' and `Hamlin' orange [Citrus sinensis (L.) Osb.] fruit were examined in 2000 and 2001. NAA effectively inhibited the reduction in FDF or fruit abscission caused by ethephon when applied to the abscission zone 24 hours before ethephon application, but had no significant effect when applied to the fruit without contacting the abscission zone, or to the peduncle ≈4 cm above the abscission zone. TIBA, an auxin transport inhibitor, decreased FDF of mature fruit and promoted fruit abscission when applied alone as a spray to the canopy or directly to the fruit peduncle. This response was dependent on TIBA concentration. TIBA was more effective when applied in combination with ethephon or CMN-Pyrazole than alone. These results are consistent with our previous data that endogenous auxin concentration in the abscission zone of mature `Valencia' orange fruit is one of the factors controlling the sensitivity and thus the responsiveness of the abscission zone of mature fruit to abscission chemicals. Chemical names used: 5-chloro-3-methyl-4-nitro-pyrazole (CMN-Pyrazole); 2-chloroethylphosphonic acid (ethephon); naphthalene acetic acid (NAA); 2,3,5-triiodobenzoic acid (TIBA).

SPRAY DEPOSITION AND ABSCISSION EFFICACY OF CMN–PYRAZOLE IN MECHANICAL HARVESTING OF VALENCIA ORANGE

Tests were conducted to investigate the efficacy of an experimental abscission chemical, CMNPyrazole(CMNP), in a commercial orange grove in south Florida. Application variables included sprayer type, spray volume rate,spray release height, and application time. Spray deposition was assessed by fluorometry and the chemical efficacy wasquantified by measuring fruit detachment force and fruit removal by a trunk shaker.<br><br>CMNP deposition decreased when spray volume increased. However, high volume applications produced betterloosening effects and fruit removal. At low volumes, nighttime application resulted in higher depositions than daytimeapplication. Spray release height had significant effects on spray penetration within the canopy, fruit detachment force, andfruit removal. Depositions on the outside and at lower canopy locations were generally higher than those on the inside andat higher canopy locations.

Physiological Factors Affecting Response of Mature `Valencia' Orange Fruit to CMN-Pyrazole. II. Endogenous Concentrations of Indole-3-Acetic Acid, Abscisic Acid, and Ethylene

Endogenous concentrations of IAA and ABA in the peel, pulp, seed, and abscission zone of mature `Valencia' oranges [Citrus sinesis (L.) Osbeck] were determined by high-performance liquid chromatography and enzyme-linked immunosorbent assay from early November 1998 to mid-June 1999. Ethylene production of mature `Valencia' oranges during the same period was determined by gas chromatography. IAA concentrations in the pulp and seed were three to five times lower than those in the peel over the 7-month observation period. IAA concentration in the abscission zone and peel was high from late April to mid-May, the period of less responsiveness to abscission chemicals. ABA concentration in the pulp was low over the entire observation period. ABA concentration in the abscission zone and peel was low during the less responsive period. Ethylene production was always low except for a slight increase during late December and early February. The IAA to ABA ratio was high in the fruit abscission zone during the less responsive period. Fruit detachment force of CMN-pyrazole-treated fruit was positively correlated with the ratio of endogenous IAA to ABA or endogenous IAA, but negatively to endogenous ABA in the fruit abscission zone. These data suggest the balance between IAA and ABA in the fruit abscission zone may be an important factor in determining sensitivity and thereby the response of mature `Valencia' orange fruit to abscission chemicals. Chemical names used: abscisic acid (ABA); indole-3-acetic acid (IAA); 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-pyrazole).

THE EFFECT OF TRUNK SHAKER PATTERNS ON FLORIDA ORANGE REMOVAL

Trunk shakers use multidirectional shaking patterns to remove oranges from trees. Bark slippage has been aproblem on some of the more susceptible orange trees using these patterns. A linear shaking pattern offered potential forreducing bark damage (slippage) but its effect on fruit removal performance was unknown. Three field experiments wereconducted in matureHamlin orange trees to measure the fruit removal performance of multidirectional and linear shakingpatterns. An abscission chemical was applied in two of the experiments to reduce the fruit detachment force of the oranges.The linear shaking pattern removed 1 to 6 percentage points more oranges than did the multidirectional shaking pattern witha 6 to 7cm displacement at 7Hz frequency and a shaking time of 5 to 10 s/tree.

SPRAY VARIABLE EFFECTS ON ABSCISSION OF ORANGE FRUIT FOR MECHANICAL HARVESTING

An experimental abscission chemical, CMN-Pyrazole (CMN-P), was applied to Valencia orange trees toinvestigate the effects of spray variables on fruit detachment force and mechanical harvesting efficiency of a trunk shaker.Spray variables included sprayer type, spray volume, ground speed, and CMN-P application rate. Harvesting efficacywas assessed in terms of fruit detachment force, pre-harvest drop of fruit, and percent fruit removal by the shaker. Atcomparable volume rates, CMN-P deposition was not significantly different for the Titan tower and AirFlow sprayers;however, harvesting efficacy was slightly better with the latter. Lower volume sprays resulted in higher deposition thanhigher volumes. However, more uniform deposition, lower fruit detachment force, and higher percent fruit removal wereobserved with higher volume sprays. Increasing the ground speed at constant sprayer output improved depositionefficiency, but more uniform spray distribution, better canopy penetration, and higher harvesting efficiencies wereobtained at lower ground speeds.

ORANGE REMOVAL WITH TRUNK SHAKERS AND ABSCISSION CHEMICALS

Trunk shake-catch systems have been used commercially to a limited extent to mechanically harvest Floridaoranges for processing for the past four seasons. In most cases, oranges left on the trees by the shakers and those missingthe catchframes must be gleaned by hand harvesters. The cost of gleaning reduces or may eliminate the profit for themechanical harvesting operation. During the past two seasons, abscission chemicals to reduce the detachment force oforanges have been tested to determine to what extent they increase the fruit removal efficiency of the shakers. This articlediscusses orange removal results with various chemicals. In general, removal efficiencies were increased 10 to 15percentage points when orange detachment forces were reduced 50 to 80%.

Trunk Shakers for Citrus Harvesting—Part II: Tree Growth, Fruit Yield and Removal

i TTAMLIN' and 'Valencia' oranges were harvested for XX5 seasons to evaluate the effectiveness of 4 trunk shaking patterns (2 linear, and 2 multidirectional, with and without abscission chemicals). Fruit yields, removal efficiencies, and trunk circumferences were measured. Hamlin yields were not affected by the shakers; Valencia yields were significantly reduced by one of the multidirectional shaker patterns. Abscission chemicals did not reduce the yields of either Hamlin or Valencia. Abscission chemicals increased shaker removal efficiencies from 64% to 90% in Hamlin and from 74% to 91% in Valencia. Trunk growth was not affected by shaking. The most vigorous linear shaking pattern provided superior harvesting efficiency.

Trunk Shakers for Citrus Harvesting—Part I: Measured Trunk Shaker and Tree Trunk Motion

THE motions of shaker and trunk were measured in 'Hamlin' and 'Valencia' oranges for two harvest seasons on linear and mulidirectional shaking patterns. Trunk amplitudes ranged from 20 to 32 mm and shaker amplitudes ranged from 21 to 30 mm. The average difference between the simultaneous position of the tree trunk and shaker ranged from 6 to 11 mm. Trunk amplitude was negatively correlated to trunk circumference. Percent fruit removal was positively correlated to trunk amplitude for the treatments without abscission chemicals.

Shakers Affect Florida Orange Fruit Yields and Harvesting Efficiency

ORANGE harvesting studies were conducted with air and trunk shakers plus abscission chemicals and compared with hand harvesting from the 1979-80 through the 1984-85 seasons. These harvesting methods were also superimposed on several tree size management practices. Severe freezes occurred during four of these seasons. The air shaker reduced yields on average of 16% while the trunk shaker reduced yields an average of 5%. Harvesting efficiencies of the air and trunk shakers average 77 and 87%, respectively. Tree size management practices did not affect the fruit removal performance or harvesting efficiencies of the shakers.

Shaker Stroke Affects Selective Removal of Valencia Oranges

ABSTRACT AN experiment was conducted to determine the effect of three shaker strokes with and without an abscission chemical on the selective removal of mature Valencia oranges as measured by subsequent fruit yields. Subsequent fruit yields were reduced an average of 15% over the corresponding initial yield for all shaker strokes. The reduction in yield was less with the 15.2 and 20.3 cm strokes compared to the 25.4 cm stroke shaker treatments. The abscission chemical (RELEASE)^ did not improve selectivity over no chemical check when the 25.4 cm shaker stroke was use..

Trunk Shaker Removal of Oranges

ABSTRACT TWO types of trunk shakers were each used in two shaking modes to harvest oranges of two major cultivars over three harvest seasons. Treatments were applied with and with no use of fruit abscission agents. Fruit removal in 'Hamlin' and 'Valencia' oranges was increased an average of 26 and 12 percentage points, respectively, by the use of abscission chemicals. The two shaking modes of the linear shaker gave the highest and lowest fruit removal results in both cultivars while the multi-directional shaker modes were in between. The shaking amplitudes obtained were not consistent from season to season. Abscission chemicals did not affect yields of either cultivar in any season but shaking treatments did significantly affect 1983 fruit yields. Trunk circumference did not affect operating frequencies of the shaker treatments. Mass removal of various deciduous fruits and nuts by means of limb or trunk shakers has been a reality for many years (Brown et al. 1983). Application of this technique to harvesting citrus has been difficult because of factors such as high fruit bonding force, machine reliability, marginal economics, and presence of dual crop in late season 'Valencia' oranges (Hedden et al. 1983). Trunk shakers, in particular, have not been accepted because of low fruit removal, bark damage, and lack of adequate tree trunk area for shaker clamp attachment in a large percentage of Florida grove conditions. Previous citrus harvesting experiments (Whitney, 1975) with a multi-directional trunk shaker achieved 98% fruit removal in 'Queen' oranges and 86% removal in 'Valenica' oranges with the abscission chemical RELEASE (5-chloro-3-methyl-4-nitro-pyrazole). Subsequent fruit yields were reduced 15% from the effects of shaker and abscission chemical. However, the potential for shaking a tree with a single attachment point, the advent of abscission chemicals for fruit loosening, and an increase in tree numbers of a size and shape adaptable for trunk shaking make this fruit removal method look increasingly attractive. The objectives of the experiments described in this paper were to determine fruit removal efficiencies and subsequent yield effects of four modes of trunk shaking.

Citrus Rollout Harvest System

ABSTRACT A citrus rollout harvest system was designed for minimum investment cost and operational risk. It consisted of a tractor-mounted limb shaker, abscission chemical, and a rollout fruit collector. A harvest capacity of 21.25 t/day (8-h) was obtained at a cost of 46.36 dollars/t. A mode of operation change was indicated that would increase the capacity to 35.39 t and decrease the cost to 33.91 dollars/t.

Citrus Harvest Mechanization in Florida-Current Situation

ABSTRACT MECHANICAL harvesting systems consisting of abscission chemicals, shakers, windrow and pickup machines, and bulk-handling trucks are economically close to competing with hand harvesting, in good grove conditions, for about 22% of Florida orange production..

Evaluation of abscission chemicals in various combinations for loosening Valencia oranges during re-greening

SummaryAll chemicals, tested alone or in combinations with Ethrel, had little effect until late in the Valencia season after January. Despite less force required to detach the fruit, the overall percentage of fruit removed declined due to natural fruit re-tightening until March, when true abscission increased with natural senescence. The combination of Ethrel+Pik-off+Harvade caused the lowest fruit detachment force, the highest fruit removal, the most true abscission and had the most consistent effects throughout the season. The next best treatments were Ethrel+Pik-off, and Ethrel alone. Ethylene production from the chemicals was highest for the triple combinations and for Ethrel and its double combinations. Natural fruit detachment had two main periods of weak fruit attachment: December-January, the physiological fruit drop period, and February- March, the early fruit senescence phase.

Shaker Methods for Selective Removal of Oranges

ABSTRACT FIVE fruit removal methods were evaluated on three dates in each of 3 years under simulated commercial conditions to determine their ability to selectively remove mature 'Valencia' oranges without damage to the follow-ing year's young fruit crop. Fruit yields were not materially affected by harvesting at 90 percent removal efficiency with shaker removal methods early in the season before young fruit drop diminished. The slider crank shaker plus abscission chemical (RELEASE) removal method reduced subsequent fruit yield the least and the air shaker plus abscission chemical method reduced subsequent yield the most. Application of the abscission chemical did not affect the subsequent fruit yield response to the shaker-catchframe removal method.

Relative Effectiveness of Dilute and Concentrated Abscission-chemical Sprays in Loosening ‘Valencia’ Oranges from Trees1

Abstract Ethylene production, hydrolytic enzyme activity, and fruit removal force (FRF) were more uniform and consistent when abscission chemicals were applied as dilute as compared to concentrated sprays to ‘Valencia’ orange (Citrus sinensis (L.) Osbeck). Cycloheximide (Acti-Aid), glyoxal-dioxime (Pik-Off), 5-chloro-3-methyl-4-nitro-1H-pyrazole (Release), and Acti-Aid plus chlorothalonil (Sweep) were applied to ‘Valencia’ orange branches, each holding 100 to 120 fruit. The FRF's resulting from commercial concentrate and dilute sprays of Acti-Aid and Acti-Aid plus Sweep were similar to those in the branch tests. Equal amounts of chemical were applied in the dilute and concentrate sprays. Likely, the variation in coverage from concentrate sprays caused ethylene levels to vary greatly in the fruit (0 to 5.7 ppm). In turn, levels of hydrolytic enzyme activity varied as much as 10×, and fruit loosening was inconsistent (0 to 9.7 kg FRF). Release and Acti-Aid plus Sweep were more consistent than Pik-Off and Acti-Aid in dilute spray applications.