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8 HARVESTING I. METHODS OF HARVESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 A. Manual Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 B. Mechanical Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 I. METHODS OF HARVESTING Harvesting is a very crucial operation in which fresh fruit is removed from the plant after completion of its growth and development. This also marks the last cultiva- tion operation for the crop in the orchard and beginning of its postharvest handling. The method of harvesting, injury to fruit during harvesting, and weather conditions during harvest greatly determine the extent of decay losses during subsequent han- dling and storage. The snap method (twisting the fruit stem and pulling) is very common in manual harvesting. Clipping is done in specialty fruit. Mechanization of fruit destined for the fresh fruit market is yet to be commercialized, although research efforts have been going on in this direction for quite some time. A. Manual Harvesting Citrus fruits are non-climacteric and they mature on the tree. Oranges and man- darins do not fall on the ground at optimum maturity. Overripe fruits fall on the ground long after the development of acceptable taste; however, it is not advisable to wait until that time. It is advantageous in that fruit can be kept longer on the tree for fresh fruit market. It depends on the maturity of the fruit and also its stem- wood, which can break while snap-harvesting or can separate at the abscission zone near the fruit. Oranges harvested in early season (November–December) do not separate at abscission zone but the stem breaks at the junction of button and the fruit stem, leaving the button attached to fruit (Fig. 8.1). This also happens in most other citrus fruits, as the natural abscission zones are at two places in 215 Citrus Fruit: Biology, Technology and Evaluation Copyright © 2008 by Elsevier Inc. All rights of reproduction in any form reserved.

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8HARVESTING

I. METHODS OF HARVESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215A. Manual Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215B. Mechanical Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

I. METHODS OF HARVESTING

Harvesting is a very crucial operation in which fresh fruit is removed from the plant after completion of its growth and development. This also marks the last cultiva-tion operation for the crop in the orchard and beginning of its postharvest handling. The method of harvesting, injury to fruit during harvesting, and weather conditions during harvest greatly determine the extent of decay losses during subsequent han-dling and storage. The snap method (twisting the fruit stem and pulling) is very common in manual harvesting. Clipping is done in specialty fruit. Mechanization of fruit destined for the fresh fruit market is yet to be commercialized, although research efforts have been going on in this direction for quite some time.

A. Manual Harvesting

Citrus fruits are non-climacteric and they mature on the tree. Oranges and man-darins do not fall on the ground at optimum maturity. Overripe fruits fall on the ground long after the development of acceptable taste; however, it is not advisable to wait until that time. It is advantageous in that fruit can be kept longer on the tree for fresh fruit market. It depends on the maturity of the fruit and also its stem-wood, which can break while snap-harvesting or can separate at the abscission zone near the fruit. Oranges harvested in early season (November–December) do not separate at abscission zone but the stem breaks at the junction of button and the fruit stem, leaving the button attached to fruit (Fig. 8.1). This also happens in most other citrus fruits, as the natural abscission zones are at two places in

215Citrus Fruit: Biology, Technology and EvaluationCopyright © 2008 by Elsevier Inc. All rights of reproduction in any form reserved.

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216 CITRUS FRUIT: BIOLOGY, TECHNOLOGY AND EVALUATION

citrus – one between the button and the stem and another between the fruit and the button with the calyx. When harvesting an orange, about 8–9 kg of fruit removal force is required to detach it from stem (Juste et al., 1988). Detachment force decreases as the fruit maturity advances.

Most of the world’s citrus crop for the fresh fruit market is harvested manu-ally. If citrus fruits are all harvested at one time, the result is a mix of good- and poor-quality fruits. For the fresh fruit market, fruit has to be spot-picked. Fruits are harvested normally by snap method, either keeping some part of the pedicel attached to the fruit or without any pedicel at all. The peel is torn off while pull-ing, particularly when mandarin fruits are over-mature and puffy, because the peel becomes brittle. In Florida, the usual method is to snap-pick, which breaks or pulls the stem and sometimes part of the button from the fruit if not properly done (Jackson, 1991). In California and Arizona, citrus fruit are clipped – particularly mandarins – to avoid the danger of infection. While a certain amount of injury to citrus fruits is unavoidable during harvesting, the extent of decay is directly

proportional to the amount and severity of injury (Eckert and Eaks, 1989).The use of ladders and some type of bag or container tied/strapped to

the back or waist of the picker is a common practice. In most areas the picker places the fruit into a canvas or plastic sack, which he then empties into a larger wooden, plastic, or metal container kept on the ground. In an improved method of picking, the bag is strapped on over the left shoulder and the picker climbs a ladder and picks fruit between the ladder rungs and on his right side. After reaching the highest point he shifts the bag to the right and picks fruit on left side (Seamount et al., 1972).

The container is then moved from the orchard to the truck for transport to the packinghouse, or the fruit is dumped from the containers into large trailers for transport to a processing plant. The fruit is transported out of the orchard by lift trucks, tractor-drawn trailers, small vehicles on rail systems (Japan), or

Abscissionat style

Abscissionat calyx

Abscissionat peduncle

Branch

FIGURE 8.1 Abscission Zones (Layers) of Citrus Fruit.

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HARVESTING 217

manually (China). Cable ways or ropeways with trolleys are used to carry fruits on steep slopes in Japan.

South African citrus is harvested traditionally by hand using specially designed clippers. Snap-picking is also common if the crop is mature and results in less rotting. In snap-harvested fruit, Alternaria rot was found to increase, but an accompanied benefi t was a greater decrease in Diplodia rot (Pelser, 1977). Therefore, fruits for export are mostly harvested by snap method. In Morocco, fruit harvest is done by hand, taking maximum care to avoid any damage to fruit that could result in decay (El-Otmani, 2003). In Australia, citrus fruit for the fresh fruit market is hand-harvested, which is a major cost to the grower. Aluminum ladders and mobile power ladders are used to reach the fruit, which is collected in canvas picking bags. Harvested fruit is collected in 0.5–1.5-tons bins and taken to packinghouses in trucks (Gallasch and Ainsworth, 1988). In Spain, harvesting is normally done manually using clippers and baskets. The fi lled baskets are unloaded into boxes of 18 kg capacity. These boxes are loaded onto trucks for transportation to the packinghouses (Juste et al., 1988).

In Florida, pickers standing on ladders (6–7 m long) generally remove the fruit and collect it in 25 kg-capacity canvas bags strapped over their shoulders. Canvas bags of 20 kg capacity and two shoulder straps are found to be conven-ient to most pickers regardless of age and sex (Grierson and Wardowski, 1986). Fruit is emptied into pallet boxes with about 400 kg capacity. These pallet boxes are then lifted with forklift trucks and loaded onto trucks for transportation to the packinghouse. In the 1950s, smaller fi eld boxes of 90 lbs capacity were used to collect harvested fruit in the fi eld. In the U.S., harvested citrus fruit is usually estimated in terms of boxes of fruit instead of tons, as in other countries. A box of oranges in Florida has net weight of 40.9 kg (90 lbs), while in California it is 31.8 kg (70 lbs). In California, a lemon box weighs 34.5 kg or 76 lbs. The Florida tangerine harvest unit is a box of 18.1 kg or 40 lbs. Grapefruit in California and Florida are harvested in a box with 36.3 kg (80 lbs) net weight. In Florida, opera-tors other than growers do the harvesting. These operators are cooperatives of growers or private fi rms. They also do marketing and maintain crews for harvest-ing, loading, and transporting. Specialized citrus dealers perform the harvesting and deliver the fruit to market.

Pickers are usually paid on a piece-rate basis but also may work at an hourly rate. In Florida, pickers are paid usually for each box rather than on an hourly basis. There is generally a crew foreman who oversees the harvesting and records the number of containers harvested by the picker. The foreman also inspects for improperly harvested fruit, such as off-sized or plugged fruit or fruit harvested with a portion of long stem attached. The long pedicel or stem may cause punc-turing of the adjacent fruit. Plugging (rind tearing) occurs in mandarin-type fruit that is not clipped, but poor harvesting leads to plugging of all citrus. In manda-rins, economic analysis usually indicates that the higher cost for clipping is jus-tifi ed. Plugging predisposes the fruit to fungal infection and desiccation during transit and packing. Foremen are also responsible for ensuring that the entire crop

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or the properly sized or colored portion is harvested from a particular orchard or area of an orchard.

Hand-harvesting is arduous work – it is diffi cult and time-consuming to harvest the fruit of large trees. Out of total harvesting time, a picker spends 75 percent and 60 percent of his time in picking (reaching and detaching) oranges and grapefruits, respectively (Coppock and Jutras, 1960). In California, a picker spends 75 percent and 85 percent of his time picking oranges and lem-ons, respectively (Ross, 1968).

In some parts of South India, acid limes and mandarins are harvested by pulling off the fruit with the help of a bamboo pole with a scythe attached to one end (Naik, 1948). Harvesting of Kinnows is conventionally done using garden secateurs and even tailors’ scissors. ‘Kinnow’ plucking scissors have also been developed. The sac-bag, basket, bucket with rope, and Israeli auto-empty bags have all been found to be inconvenient. A harvesting device with fl exible, wire-reinforced PVC tube with an enlarged feeding mouth has been developed. The picked fruit has to be put into the tube by the picker; the fruit then rolls down to the ground (Jai Singh, 1999). ‘Nagpur’ mandarins are harvested by the snap method using ladders and bags and sometimes clippers. Pickers collect fruit in a bag or a cloth tied around the waist and collect in round baskets made of bam-boo. Fruits are heaped at one place in the orchard on paddy straw and sorted before transportation. Sweet oranges are manually picked by snap method and collected in bags. For ‘Sathgudi’ oranges, careful clipping with shears, leaving 2 mm of stem, is recommended (Satyanarayana and Ramasubba Reddy, 1994). Sweet oranges and acid limes on the lower part of the canopy, which is eas-ily accessible, are picked by the snap method and collected in bags. To reach acid lime fruit at the top and inside of the canopy, a pole with hook is used and dropped fruits are collected. This is a common practice in some parts of India because acid lime trees are large and thorny. Usually the ground is plowed and soft and most of the time grass or polyethylene or cloth is spread on the ground so that fruit is not damaged (Fig. 8.2, see also Plate 8.1).

The speed of harvesting is slower in clipping because both the hands of picker are engaged in harvesting one fruit. In snapping, picker can harvest two fruits at a time. A picker can harvest 350 ‘Nagpur’ mandarin fruits in an hour by the snap method as opposed to 316 by clipping. The speed of harvesting also depends on the bearing habit of the tree and how much time the picker has to spend to reach the fruit. If mobile, height-adjustable platforms are used instead of ladders, the effi ciency of picker is likely to increase because it will be con-venient for him to reach the fruit. In Cuba, oranges are harvested using a multi-stand harvesting platform. Harvesting productivity using platforms is 0.48 ton/ha greater and labor requirements and costs are less than conventional manual harvesting (Alonso et al., 1989).

Keeping labor availability and consumption patterns in mind, hand-picking continues to be the only method of harvesting citrus fruits in India and many

218 CITRUS FRUIT: BIOLOGY, TECHNOLOGY AND EVALUATION

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HARVESTING 219

other underdeveloped and developing countries in the near future. More than 95 percent of produce is consumed fresh and hence mechanical harvesting, which is expensive and most likely to cause bruises and injuries, has little scope in the near future.

1. Injuries to Fruit

Careful harvesting and handling are very important to maintain fruit qual-ity. Although most citrus cultivars have a rigid, tough peel, poor or delayed han-dling in the fi eld has a signifi cantly deleterious effect on subsequent fruit quality. Reduced fresh marketing is often related to poorer handling, resulting in unrelia-ble delivery condition of the fruit (Grierson, 1981). Fruit for export must be picked with reasonable care, even if a premium has to be paid to ensure this. Oleocellosis is the common hazard and peel turgor should be less. Injury should be minimal to the stem end. The pulling (snapping) method can be preferable to clipping if it is done carefully without plugging. No fruit should ever touch the ground. Care should be taken that pallet boxes are not fi lled above the top rim. Lemons are to be picked only in rigid framed bags, and once picked, the fruit should be shaded from sun. Oranges and mandarins should be hauled as quickly as possible and never allowed to dry out. Lemons are left undisturbed in the shaded grove for a day or two (for slight water loss/curing) to avoid injury to the peel.

Bruising, plugging, stem-end tears, scratching, and pitting of fruit are com-mon injuries observed in fruits collected from pallet bins (Burns and Echeverria,

FIGURE 8.2 Harvesting of Acid Lime with a Hook as a Practice in Central India. Note the Plain Field Inside the Canopy Covered with Cloth to Avoid Fruit Injury and Contact with Soil.

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220 CITRUS FRUIT: BIOLOGY, TECHNOLOGY AND EVALUATION

1990). Maximum damage is observed at pallet bin collection at the packinghouse. Improper harvesting and handling cause extensive fruit injuries and immediate decreases in pack-out percentages for fresh fruit as well as later increases in decay during storage or transit.

Plugging (rupture of skin at stem-end) or severe button-hole injury and longer peduncle were observed in ‘Nagpur’ mandarin fruit harvested by conven-tional methods. Harvesting injuries in the form of button holes at the stem-end have been found to be 8.79–9.14 percent in snap-harvested fruit as compared with negligible (less than 1 percent) injury in clipping. As a result of longer pedicels left on the fruits, particularly during clipping, puncture injuries were recorded in another 1.72 percent of fruits (Sonkar et al., 1999). In the spring-blossom crop, plugging and slight skin rupture at the stem-end (near the collar) accounted for 4.3 percent and 4.49 percent of injured fruit, respectively in snap method. Longer stems/pedicel (10–40 mm and even longer) on 1.58 percent of fruits resulted in injury to 0.25 percent fruits during harvesting and handling operations (Fig. 8.3, see also Plate 8.2). In the monsoon- blossom crop harvested in February–March, the extent of injury or plugging at the stem end has been very low (�0.5 percent). In warm and dry weather – particularly if irrigation is stopped at least 2–3 weeks before harvest – fruit can be readily harvested by snapping. Higher injuries to fruit in the spring-blossom crop harvest season is probably due to more moisture con-tent in peel, resulting in brittleness. This may also result in the slowing of abscis-sion-zone formation. In general, the relative humidity range in spring-blossom (November–December) and monsoon-blossom crop season (February–April) are 60–70 percent and 30–40 percent, respectively. Low humidity in the February–March season results in drying of the stem (a sort of stress) and easy detachment of fruit.

FIGURE 8.3 Injury to ‘Nagpur’ Mandarin Caused Due to Long Stems of Other Fruit during Handling.

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HARVESTING 221

It is observed that at times, ‘Nagpur’ mandarin fruits with greener stems (where a normal abscission layer is not formed) are harvested by the pickers keeping longer stems/pedicels. In the snap method, the pedicel/button usually does not remain attached to the fruit. However, when the pedicel is still green though the fruit is mature, the picker has to struggle to harvest these fruits. Thus longer stems are left on such fruit, which can injure other fruit. Clippers can be selectively used to harvest such fruit.

In Kinnow mandarins, conventional harvesting methods have been found to cause injuries to fruit. With use of garden secateurs and scissors, a 4–5 mm peduncle is left on the fruit, resulting in puncture damage to 17 percent of other healthy fruit (Jai Singh, 1999).

Christ (1966) showed that the amount of Penicillium decay in Navels and Valencias could be directly correlated with the level of injury infl icted during commercial picking and packing. In clipped ‘Nagpur’ mandarin fruit, whether treated or non-treated with fungicidal wax, decay losses were signifi cantly less as compared with snapping (Sonkar et al., 1999). Although the harvesting rate is slightly less in clipping, the injuries to fruit and subsequent decay can be consid-erably reduced by this method. Since harvesting injuries are more frequent in the spring-blossom crop, the decay losses are likely to be greater in stored fruit of this season. This corroborates with and proves the popular belief among growers and traders that ‘Ambia’ crop (spring-blossom) fruits have low keeping quality (due to decay losses).

The addition of 2.4-D as ethyl ester (500 ppm) in fungicidal wax resulted in a higher percentage of greener pedicels in clipped ‘Nagpur’ mandarin fruit after storage. In 2.4-D-treated lemons, Stewart et al. (1952) reported delayed button deterioration and a reduced rate of coloration and water loss during storage. The vitality of the fruit button is considered to be the major impediment to develop-ment of stem-end rots. To keep buttons green, 2.4-D applications to lemons is a commercial practice in California (Eckert and Eacks, 1989). Wax (highshine wax 2.5 percent) treatment with 2.4-D (500 ppm) and carbendazim (2000 ppm) reduced decay from Penicillium rot, particularly in clipped ‘Nagpur’ mandarin fruit. The carbendazim treatment was ineffective, especially in snap-harvested fruit with slight to severe injury (Sonkar et al., 1999).

2. Cost of Manual Harvesting

Harvesting and handling costs of citrus fruit often equal or exceed total pro-duction costs of the crop. The pickers’ rate of harvesting varies depending on the kind of fruit (for example, orange or mandarin, diffi culty in picking etc.). The total costs of picking, loading, and handling to the plant have been lowest for grapefruit (73.8 cents/56 lit equivalent) and highest for tangerines (1.62 US$/56 lit equivalent) in 1976–77 (Brooke and Spurlock, 1977). Spain is a major producer and exporter of fresh citrus. Fruit harvesting accounted for more than 25 percent of the total produc-tion costs, entailing 50–60 percent of hand labor used in cultivation. The high costsand shortage of labor for harvesting poses a major problem (Juste et al., 1992).

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222 CITRUS FRUIT: BIOLOGY, TECHNOLOGY AND EVALUATION

In mandarins, economic analysis indicated that the higher cost for clipping (because of a slower rate of harvest) is justifi ed (Davies and Abrigo, 1994), keep-ing harvesting losses in mind.

B. Mechanical Harvesting

Mechanical harvesting has been tried since the 1970s in Florida for fruits sent for processing. Although most of the world’s fresh citrus fruits are harvested manually, research on mechanical harvesting continues to develop the system with fewest bruises and least damage to fruit at a lower cost of picking. Injuries to fruit at the time of harvesting lead to subsequent decay. The percentage of splits, fruits with stems attached, and punctured fruits is higher in mechanically harvested fruits than in manually picked fruits (Whiteny et al., 1973). Fungicide (thiabendazole) treatment has been found to reduce decay in mechanically har-vested fruit (Rekham and Grierson, 1971). Keeping in mind labor problems, individual fruit picking using robotics is being considered as a long-term solu-tion in Spain. The mechanical harvesting work for fresh citrus is focussed on this aspect of robot development (Juste et al., 1992).

There are several problems in the mechanical harvesting of citrus fruits. Valencia oranges particularly pose problems because two crops are on the tree (the mature crop of the current season and the green small fruits and even bloom of next year’s crop). Mechanical harvesting of fruit destined for processing using mass removal method is usually stopped during peak bloom until immature fruit is 6 mm in diameter (late April to May). Juste et al. (1992) list the major prob-lems encountered in mechanization of harvesting of fruit as follows:

1. The presently used harvesting machinery is very large, while fi eld holdings are small with varying tree sizes, spacing, and age.

2. Irrigation layouts and soil-management practices are different in different fi elds.

3. In many countries, citrus is grown on slopes, presenting diffi culties for mechanization.

4. Breakage of limbs and damage to fruit.5. Cost/benefi t ratio.6. Some leftover fruit after mechanical harvesting has to be manually

removed.7. Adverse effect of loosening chemicals on tree physiology.

These problems are specifi cally related to the Spanish citrus industry considering the use of mass-removal machines, but these constraints are true for many other citrus-growing areas.

In mechanical harvesting where a robot arm is used, the detection of fruit and its selective picking under fi eld conditions at the desired rate of picking is also a major challenge keeping in view that fruit is destined for the fresh fruit market.

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HARVESTING 223

1. Mechanical Harvesters

Mechanical harvesting machines can be broadly classifi ed as contact machines and mass-removal machines (Coppock, 1978; Coppock et al., 1981). The contact machines consists of (1). the positioning mechanism and (2). the picking hand or arm. The mass-removal machines operate by applying external force, shaking the limb or tree trunk mechanically by holding it or applying force in the form of a jet of water or air to vibrate limbs, foliage, and twigs. In mass-removal machines, fruit drops onto padded catch frames or is allowed to drop on plowed ground. Fruit is collected in pallet bins or open trucks and transported. In general, mass-removal type mechanical harvesting is suitable for fruit destined for processing (Whitney, 1978), while contact machines are useful for harvest-ing fruit destined for fresh consumption. The contact machines are based on the principle of selective picking and may use mechanical fi ngers, which are fl exible and imitate human fi ngers (Chen et al., 1982).

For citrus destined for the fresh fruit market, robots or mechanical arms and the torsion method of detachment is considered effective because the calyx is not removed. The distribution of fruit in the canopy has to be considered in designing a robot. The cultivars with maximum fruits in the outer periphery are most suitable since electronic detection and selection is easier. Satsumas and Clementines are the most suitable for this purpose, as 80 percent of the fruit is available 70 and 30 cm from the periphery, respectively in these cultivars. Fruits of Washington Navel and Salustiana oranges are borne 140 and 100 cm inside the periphery, respectively (Juste et al., 1988). According to Juste et al. (1992), some promising results have been obtained in developing prototypes of mechani-cal arms, vision systems, fruit detectors, and end effectors. Fruit peduncles in 85 percent of fruit have been less than 5 mm and 98 percent of fruits presented intact calices. The injuries to fruit have been negligible to none. The system is very useful for fruit destined for the fresh fruit market.

The use of spectral refl ectance and chrominance information to enhance digital color images to control a robotic manipulator for harvesting is possible (Slaughter and Harrell, 1987; Slaughter et al., 1986). The spectral information is useful to differentiate the fruit image from background leaves, tree limbs, soil, and sky. The ability to harvest citrus fruits automatically by means of image processing (vision system) has also been investigated by Kawamura (1985). The fi eld conditions pose diffi culties in fruit recognition by automatic mechanical systems or robots for selective harvesting of fresh fruit. The important task for the robot is to recognize fruit against varying backgrounds (green leaves, blue sky, brown branches, and black soil) that have different colors under different light conditions. Fruits are also clustered most of the time. Cerruto et al. (1996) conducted experiments in which images of fruit are taken in RGB (red, green, and blue) system and analyzed under HIS (hue, saturation, and intensity) system because the HIS system offers several advantages, and recognition by this system is very close to the human eye. These researchers have reported real-time fruit recognition by color imaging using video cameras. The automating of system

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224 CITRUS FRUIT: BIOLOGY, TECHNOLOGY AND EVALUATION

settings and procedures for different light conditions is likely to provide recogni-tion without error. Molto et al. (1998b) reported usefulness of machine-vision technology to properly detect oranges and the exact location of the stem based on image analysis. The electronic arm of the harvester therefore will be able to identify and selectively harvest fruits under the grove conditions.

On the large commercial plantations of Florida and Brazil, where fruit is mostly utilized for processing, mechanization is benefi cial as the manual har-vesting is becoming uneconomical and laborers are not available when needed. Effi cient mechanical harvesting is a key factor in economical fruit production for industrial processing. Mechanical harvesting by a conventional trunk shaker works well in young and uniform orchards, where shaker parameters are pre-adjusted to the uniform trees. In an old or non-uniform orchard, most shakers cannot be operated properly unless the shaker properties are adjusted to the indi-vidual tree during the harvesting operation (Galili et al., 1999).

The Florida Department of Citrus has been working with inventors and manufacturers to develop technologies that reduce harvesting costs for process-ing oranges and increase worker productivity (Brown, 1998). Mechanical har-vesting systems are in various stages of development and fruit-abscission compounds are being evaluated. Peterson (1998) has described an experimental, direct-drive, double-spiked-drum canopy shaker to harvest oranges from high-density groves. The drums have horizontal whorls on a vertical shaft and each whorl has nylon rods that penetrate the canopy up to 1 m. Shaking frequency is 4–5 Hz, with maximum horizontal displacement of the rod tip of 250 mm. The shaker can be towed by a tractor along a tree row at travel speeds of 1.4–3.2 km/h.In the canopy space penetrated by the shaking rods, mature fruit removal aver-aged 71–91 percent. The shaker drums are 3.66 m in diameter with height to har-vest trees up to 4 m high. Fruit catching and conveying components are added under the shaker mechanism to collect and transport the detached oranges to the rear center of the shaker unit. A self-propelled bulk transport unit follows the harvest unit at a synchronized speed. The bulk transport unit has a conveying system that receives the oranges from the harvester and transfers them to its rear hopper (with a 6-ton capacity). The system has trash-removal devices also. The grade of fruit received at the processing plant has been as good as hand-harvested fruit.

Trunk shake-catch systems are being commercially used to some extent to mechanically harvest Florida oranges for processing. Whitney and Wheaton (1987) studied the effi ciency of air and trunk shakers plus abscission chemicals for orange harvesting. Harvesting effi ciencies of the air and trunk shaker aver-aged 77 percent and 87 percent, respectively. Tree-size management practices did not affect the fruit-removal performance or harvesting effi ciencies of the shakers.

Fruits left on the trees by the shakers and those missing the catch frames must be gleaned by hand harvesters. The cost of gleaning reduces or may elimi-nate the profi t for the mechanical harvesting operation. Abscission chemicals to reduce the detachment force of oranges are being tried to increase the removal

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HARVESTING 225

effi ciency of the shakers. Shaker removal effi ciencies increase by 10–15 percent when orange detachment force is reduced 50–80 percent (Whitney et al., 1999).

2. Loosening Chemicals

In mass-removal harvesting, some chemical aids (plant growth regula-tors, particularly abscission agents) are applied so as to loosen the fruit before mechanical harvesting. The effects of these chemicals and the mass-removal method of mechanical harvesting have been studied by several researchers. The important criteria that abscission chemical should meet are (1) selective action on mature fruit within 3–4 days and (2) non-phytotoxic. The chemical should also be inexpensive and eco-friendly.

Ethephon (350 ppm) reduced the fresh fruit quality of Washington Navel oranges and increased wastage, while ‘Pick-off’ (glyoxal dioxime, 200 ppm) increased wastage in Valencias (El-Zeftawi et al., 1978). Mechanical harvesters reduced fruit quality and increased wastage in all varieties and losses were higher in Washington Navels. Different types of mass mechanical shakers have different impacts and the extent of losses varied. Burns et al. (2005) reported that appli-cation of abscission agent ‘Release’ (5-chloro-3-methyl-4-nitro-1H-pyrazole, CMPN, 17 percent a.i.) ranging from 10–500 ppm at 300 gallons/acre to Hamlin and Valencia trees increased the harvesting capacity of trunk and canopy shak-ers by reducing the time necessary to harvest each tree while maintaining a high percentage of mature fruit removal. CMPN is selective and non-phyto-toxic.

In various methods of mechanical harvesting (limb shakers, air-blast and trunk shakers, foliage shakers, and robotic arms), when abscission chemicals are not used, a large percentage of fruit comes off with stems that could puncture adjacent fruit during the transporting and handling processes. The de-stemming machine (including roller-cutter assembly) and the oscillating conveyer have been reported to cut stems of oranges at a speed of one fruit per second with destemming of 90–95 percent of the fruit (safe length of 3 mm) fed on the machine (Chen, 1994).

3. Cost of Mechanical Harvesting

The increased necessity of mechanical harvester is mainly due to rising labor costs. According to estimates of Brooke and Spurlock (1977), at least 105 ha of fruit needs to be harvested annually for mechanical harvesting to be cheaper than hand-picking. One trunk shaker and catch system harvests 90–140 trees/h. Adoption of the mechanical harvester eliminates fi ve jobs for each job of equipment operator it creates. Mechanical harvesting is an important tool that enables the Florida citrus industry to be competitive in a global juice mar-ket (Futch and Roka, 2004). Growers save 20–50 percent per box compared to conventional harvesting systems. In Sao Paulo (Brazil), the cost of harvesting one box is 0.52 US$, while in Florida it is relatively higher. Therefore, more and more growers are following mechanical harvesting (Neff, 2004).

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226 CITRUS FRUIT: BIOLOGY, TECHNOLOGY AND EVALUATION

REFERENCES

Alonso, A., Cardenas, T., Sadourian, S., and Suarez, J.L. (1989). Technical – economic evaluation of multi-stand platform APC – 9 M in citrus fruit harvesting. Ciencia Y Techica en la Agric.: Mecaniza cion de la Agric. 12, 15–22.

Brooke, D.L., and Spurlock, A.H. (1977). Production costs – fruit production, harvesting, packing-house, processing. In Citrus science and technology (S. Nagy, P.E. Shaw, and M.K. Veldhuis, eds.), Vol. 2. AVI Publishing Co., Westport, CT, USA pp. 141–170.

Brown, G.K. (1998). Florida citrus can be mechanically harvested. ASAE Annu. Int. Meeting, Orlando, FL, USA, 12–16 July 1998, 6 pp., ASAE Paper no. 981091.

Burns, J.K., and Echeverria, E. (1990). Quality changes during harvesting and handling of ‘Valencia’ oranges. Proc. Fla. State Hort. Soc. 103, 255–258.

Burns, J.K., Buker, R.S., and Roka, F.M. (2005). Mechanical harvesting capacity in sweet orange is increased with an abscission agent. Hort. Technol. 15, 758–765.

Cerruto, E., Manetto, G., and Schillaci, G. (1996). Trials on citrus fruit recognition by colour image. Proc. Int. Soc. Citric, Sun City, South Africa, pp. 1122–1125.

Chen, P. (1994). Mechanical de-stemming of oranges. In ‘Post-harvesting operations and quality sensing’ (F. Juste, ed.). IVth Int. symp. fruit veg. prod. Engg., Valencia, Spain, Vol. 2, pp. 205–221.

Chen, P., Mehischan, J., and Ortiz-Cafl avate, J. (1982). Harvesting Valencia oranges with fl exible curved fi ngers. Trans. ASAE 25, 534–537.

Christ, R.A. (1966). The effect of handling on citrus wastage. S. African Citrus J. 587, 7, 9, 11, 13, 15.Coppock, G.E. (1978). Mechanical harvesting and handling citrus fruits. Proc. Int. Soc. Citric. Int.

Citrus Congress, Australia, pp. 87–91.Coppock, G.E., and Jutras, P.J. (1960). Mechanizing citrus fruit harvesting. Trans. ASAE. 3(2),

130–132.Coppock, G.E., Sumner, H.R., Churchill, D.B., and Hedden, S.L. (1981). Shaker method for selective

removal of oranges. Trans. ASAE. 24, 102–104.Davis, F.S., and Albriago, L.G. (1994). Citrus. CAB International, Wallingford, Oxon, UK, 254 pp.Eackert, J.W., and Eaks, I.L. (1989). Postharvest disorders and diseases of citrus fruits. In ‘The citrus

industry’. (W. Reuther, E.C. Calavan, and G.E. Carman, eds.) Vol. V, pp. 179–260. Divinan. Agriculture Science University of California, Berkeley, California.

El-Otmani, M. (2003). Citriculture in Morocco. Citrus Ind. 84 (11), 22–23.El-Zeftawi, S.M., Thornton, I.R., and Gould, I.V. (1978). Effects of mechanical shake-removal on

citrus fruit quality. Proc. Int. Soc. Citric. Int. Citrus Congress, Australia, pp. 106–109.Futch, S.H., and Roka, F.M. (2004). Trunk shaker mechanical harvesting system. Citrus Ind.

85(7), 20–21.Galili, N., Rubinstein, D., and Shdema, A. (1999). Adaptive shaker for mechanical harvesting of olives

and citrus fruits. ASAE-CSAE-SCGR Ann. Int. Meeting, Toronto, Ontario, Canada, July 18–21, 1999, 13 pp., ASAE Paper No. 997061.

Gallasch, P.T., and Ainsworth, N.J. (1988). Developments in the Australian citrus industry. Proc. 6th Int. Citrus Congress, Israel, Vol. 4, pp. 1613–1623.

Grierson, W. (1981) Harvesting Florida citrus for overseas export. Proc. Fla. Sta. Hort. Soc. 94, 252–254.

Grierson, W., and Wardowski, F. (1986). Transportation to packing house. In Fresh citrus fruits (W. Wardowski, W. Grierson, and S. Nagy, eds.), AVI Publishing Co., Westport, CT, USA. pp. 227–242.

Jackson, L. (1991). Citrus growing in Florida. University of Florida Press, Gainesville, FL, USA, 293 pp.

Jai Singh (1999). Equipments to mechanize harvesting and handling Kinnow. Proc. Nat. Symp. Citri-culture, Nagpur, 17–19, 1997. NRCC, Nagpur.

Juste, F., Gracia, C., Molto, E., Eranez, R., and Castillo, S. (1988). Fruit bearing zones and physi-cal properties of citrus fruits for mechanical harvesting. Proc. 6th Int. Citrus Congress, Israel, Vol. 4, pp. 1801–1809.

Ch08-P374130.indd 226Ch08-P374130.indd 226 11/12/07 1:41:39 PM11/12/07 1:41:39 PM

HARVESTING 227

Juste, F., Ferres, J., Pla, F., and Sevila, F. (1992). An approach to robotic harvesting of citrus in Spain. Proc. Intn Soc. Citric, Italy, pp. 1014–1018.

Kawamura, N. (1985). Vision of fruit for the development of fruit harvesting robots. Proc. Third Int. Conf. on Physical Properties of Agricultural Mater., Prague, Czechoslovakia, pp. 445–450. Agri-cultural Engineering Department, Kyoto Univeristy Japan.

Molto, E., Ruiz, L.A., Aleixos, N., Vazquez, J., and Juste, F. (1998). Machine vision for non-destructive evaluation of fruit quality. Acta Hort. 421, 85–90.

Naik, K.C. (1948). South Indian fruits and their culture. P. Varadachari Co. Madras. 335 pp.Neff, E. (2004). Mechanical harvesting: it is all about the costs. Citrus Ind. 85(4), 18.Pelser, P. (1977). Postharvest handling of South African citrus fruit. Proc. Int. Soc. Citric., Florida

Vol. 1, pp. 244–249.Peterson, D.L. (1998). Mechanical harvester for process oranges. Appl. Engg. Agric. 14(5), 455–458.Rackam, R.L., and Grierson, W. (1971). Effect of mechanical harvesting on keeping quality of Florida

Citrus for fresh fruit market. HortScience 6, 163–165.Ross, J. (1968). Multiman picking machines and systems in California. Proc. First Int. Citrus Symp.,

California, Vol. 2, pp. 647–651.Satyanarayana, G., and Ramasubba Reddy, M. (1994). Citrus cultivation and protection. APAU and

Department of Horticulture, Andhra Pradesh, Walley Eastern Ltd. New Delhi. p. 66.Seamount, D.T., Nash, P., and Opitz, K.W. (1972). An improved method of ladder and bag picking.

Citrograph. 58(11), 397–398.Slaughter, D.C., and Harrell, R.C. (1987). Colour vision in relative fruit harvesting. Trans. ASAE

30(4), 1144–1148.Slaughter, D.C., Harrel, R.C., Adsit, P.D., and Pool, T.A. (1986). Image enhancement in robotic fruit

harvesting. Trans. ASAE 29, 1137–1152.Sonkar, R.K., Ladaniya, M.S., and Singhs (1999). Effect of harvesting methods and post- harvest

treatments on storage behaviour of ‘Nagpur’ mandarin (Citrus reticulata Blanco) fruit. Indian J. Agric. Sci. 69, 434–437.

Stewart, W.S., Palmer, J.E., and Heild, H.Z. (1952). Packing house experiments on the use of 2,4-trichlorophenoxy acetic acid and 2,-4-5 trichlorophenoxy acetic acid to increase storage life of lemons. Proc Am. Soc. Hort. Sci. 59, 327–334.

Whitney, J.D. (1978). Air-shakers for removal of oranges in Florida. Proc. Int. Soc. Citric, Australia. pp. 91–93.

Whitney, J.D., and Wheaton, T.A. (1987). Shakers affect Florida orange fruit yields and harvesting effi ciency. Appl. Engg. Agric. 3, 20–24.

Whitney, J.D., Hartmond, U., Kender, W.J., Burns, J.K., and Salyani, M. (1999). Orange removal with trunk shakers and abscission chemicals. ASAE-CSAE-SCGR Ann. Int. Meeting, Toronto, Ontario, Canada, 18–21 July 1999, 9 pp. ASAE Paper No. 991078.

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CITRUS FRUIT: BIOLOGY, TECHNOLOGY AND EVALUATION

PLATE 8.1 Harvesting of Acid Lime with a Hook as a Practice in Central India. Note the Plain Field Inside the Canopy Covered with Cloth to Avoid Fruit Injury and Contact with Soil.

PLATE 8.2 Injury to ‘Nagpur’ Mandarin Caused Due to Long Stems of Other Fruit during Handling.

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