Producción de frutas y hortalizas
  


Current Situatuon of citriculture in Marocco
Mohamed El-Otmani
Department of Horticulture, Institut Agronomique et Vétérinaire Hassan II
melotmani@iavcha.ac.ma


Economic importance and destination of the production

In Morocco citrus in cultivated on a total area of 76310 ha with an annual production of » 1.4 million metric tons. This industry employs thousands of workers at various levels of production, transport, packing, etc. in the farm and post-harvest.
Morocco has a Mediterranean climate with cool winter temperatures and citrus fruit develops good taste and acceptable color for fresh consumption. In fact » 50% of the crop is exported as fresh fruit and ~40% is consumed fresh in the domestic market . Only ~10% goes to processing. Export markets are mainly the European Union (50% of total export), Canada, Russia, the USA and the Arab Gulf States. Export value is estimated to 300 million USD/year.

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Production areas

Citrus is grown in 6 major areas located within the latitudes of 30° and 35° North (Fig.1) within which producing distctricts are localized because of climate, topography and water availability. In fact, rainfall rages from 600 mm in the Northernmost area (Loukkos) and 200 mm in the Southernmost area (Souss). Therefore, citrus is irrigated almost all year round with the lowest water needs in the writer (Nov.-Jan.) and the greatest needs in the summer (June-Sept.)
The soils are generally of the heavy type, calcareous and low in organic matter. Soil pH ranges from 7.0 to 8.6 in most areas.
The Gharb area, on the Atlantic coast, produces essentially oranges with Valencias and navels dominating (Tables 1 and 2). Because of its low range and humidity in the fall and winter, the Souss and Oriental districts have most of the clementine acreage of the country (70% of the total). The inland areas of Haouz (Marrakech) and Tadla (Beni Mellal) produce mainly Valencias and navels. The Loukkos district has sandy soils allowing for rapid drainage of rainfall water and produces mainly clementines.
Table 1 shows that the largest citrus acreage is located in the Souss region followed by the Gharb. In addition, in terms of yield, the Souss has the greatest values since 52% of the total tonnage is produced on only 37% of the total area (Tables 1 and 2). The Souss area is characterized by younger orchards, use of up-to-date fertigation and other cultural practices and employment of highly qualified managers and technical manpower. Yield is lowest in the Gharb and Tadla districts as these have some of the oldest groves with many trees showing virus symptoms such as psorosis and stubborn or cryptogamic diseases such as phytophthora gummosis lesions and gumming at the bud union.



Fig.1 Citrus growing regions of Morocco

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Table 1

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Table 2

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Varieties, rootstocks and period of production

Citrus acreage has remained relatively steady for the last 10 years and production fluctuates in the range of 1 to 1.5 million metric tons depending on climate and the cycle of the alternate bearing cultivars.
Because of its Mediterranean climate with cool Autumn nights and Winters and warm Springs and Summers, citrus fruit is produced from late September (for the early clementine mandarins such as the ?Marisol? and the ?Bekria?) to the end of June (for the late cultivars such as the ?Valencia? late orange). The variety profile is very diverse with some 30 commercial varieties but only 3 fruit types predominate:

1) The clementine group with several selections (?Bekria? (early selection), ?Cadoux? (Fig. 3), ?Nules?, ?Larache?, ?Sidi Aïssa? (mid-season selections) ?Muska? and ?Nour? (late selections; Fig. 2). Currently, clementine is the most sought citrus fruit for fresh consumption because of its easy peeling, taste and aroma.



Fig. 2. Heavy crop on "Cadoux" clementine trees.

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Fig. 3. Mature fruit of "Musaka" and "Nour" clementine.

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2 ) The navel group with the ?Washington? dominating over the other selections such as ?Navelate? and ?Thomson?. ?Lane late? navel is increasing in area. The ?Washington? matures in November and ?Lane late? matures in February-March.
3) The orange group: ?Salustiana? orange and blood oranges such as ?Sanguinelli? mature in January-February. The blood oranges are essentially located in the Gharb area where the climate is warm and humid. ?Valencia? late, more known to Moroccans as ?Maroc? late, is the most dominant orange type (Tables 1 and 2) making up 36% of total annual production.
In the mandarin group, ?Ortanique?, ?Nova?, ?Afourer? (a Moroccan selection of the ?Murcott? citrus type but seedless when planted in solid blocks and far away from any pollinators; Fig. 4) and ?Fortune? constitute the major cultivars representing this citrus type. ?Ortanique? and ?Fortune? are greatly declining in acreage because of their erratic yields and postharvest quality problems. ?Ortanique? fruit is difficult to peel, and often too big in size, whereas ?Fortune? is often too small, acidic and presents crease problems if left on the tree too long. Both cultivars also have the problem of splitting although to a much lesser extent than for ?Nova?.
Morocco also produces some lemons and grapefruit but only for domestic consumption.



Fig. 4. Young tree of "Afourer" mandarin.

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Propagation, rootstocks and planting densities

Scion varieties are mostly propagated by budding on rootstocks. Propagation is under the responsibility of 4 registered nurseries where tree production follows the national tree certification scheme and the trees are certified as 1) free of tristeza, exocortis, psorosis, stubborn and cachexia-xyloporosis, viral diseases and 2) ?true-to-type?. Propagation is done under greenhouses (Fig. 5) using a substrate composed of 2/3 virgin soil +1/3 sand complemented with a little organic manure.
Until the 1980?s the most current tree spacing was varied from 6x7 to 5x 6, mXm for both oranges and clementines. Recently, several spacing were tested by various growers including various combinations of 3x4, 4x4, 4x5, 3x6 mXm, etc. However, 4x6 and 3x6 are becoming the most common spacings, respectively for oranges and clementines.



Fig. 5. Citrus propagation under greenhouse.

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Sour orange has been the ideal citrus rootstock in Moroccan soils, characterized by their high pH mostly due to their high lime content. This rootstock is resistant to Phytophthora gommosis common in heavy soils, wet areas such as the Gharb and even more common where flood irrigation is common practice. However, with the risks of tristeza introduction and outbreaks, there is a move towards diversification of rootstocks and many new orchards are planted on ?Troyer? or ?Carrizo? citranges. A few hectares have recently been planted on Citrus macrophylla and Citrus volkameriana.


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Irrigation, fertilisation and soil surface management

Irrigation is necessary all year round except during the periods of heavy rains. Implementation of water-saving technologies and irrigation systems in the farms is increasing every year. In many cases, water needs are calculated using information obtained from Class A Evaporative Pan. Daily evaporation can reach 14 mm/day in the Summer and less than 3 in the Winter. In many other cases, water supply is very empirical and approximate.
Fertilisation is based on conventional procedures using foliar and soil analyses as well as tree current and potential yield. On the average, growers supply 180-250 units of nitrogen, 60-120 units of P2O5 and 150-220 units of K2O. Application is from February to August for early-maturing varieties such as clementines and from April to early October for late-maturing varieties such as ?Valencia? orange locally named ?Maroc Late?. For the late cultivars, N application starts in April for groves that are harvested and can start as late as June for those plantations that are harvested late. This is because N enhances the regreening process in the fruit rind which takes place under hot weather of Spring months particularly in the warm areas such as the Souss Valley with the heat influence from the nearby desert. Fertilisation in the areas where water is scarce is essentially by fertigation (Fig. 6) using drip or microsprinklers but continues to be done by hand with 3 applications a year in the groves where flood irrigation is used. Because the soils are highly calcareous, micronutrient deficiencies occur, particularly for iron, zinc, manganese, cupper and magnesium. Consequently, foliar applications of microelements are common in the Spring.



Fig.6. A citrus orchard with its fertigation station.

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Weeds are common in periods following rain and in the irrigated parts of the orchards. Herbicide usage is not common but weed control is done manually or by soil tillage at least 2-3 times a year using tractors.

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Pruning and fruiting

Pruning of citrus trees starts from the nursery where the trunk height is set by heading the trees which usually develop a single main central stem. After removal of apical dominance, the tree develops lateral branches from which 3 to 4 are kept and the rest is removed. Young trees are shaped on these main scaffold branches during the initial years of planting. For mature trees pruning is a yearly operation in clementine plantings but is often an every-other-year operation in the orange plantings. It is generally performed immediately after harvest and entirely by hand using hatches, handsaws and clippers.
Use of gibberellic acid to increase fruit set is a common practice on clementines with application during the stage of full bloom-to-petal fall. In addition, clementine fruits are generally small and various auxin-like substances are used to increase fruit size with application during the end of the physiological drop.
In areas where frequent winds occur, wind breaks are a very important component of a citrus planting because winds can cause severe flower and fruit drop, and severe scarring and damage to the remaining fruit, thus making the fruit valueless and increasing packinghouse discards.

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Pests and diseases

The list of insects and mites attacking citrus is long but four constitute key pests for Moroccan citriculture. California red scale (Aonidiella aurantii) can cause damage on fruits, leaves and twigs. Its control measures still heavily rely on insecticides (organo-phosphates mainly) but biological control using Aphytis is being introduced into the pest management scheme of many orchards. Timing of treatment is based on monitoring the scale population and composition.
The Mediterranean fruit fly (Ceratitis capitata) can also cause serious damage when its population increases beyond a threshold limit. Its control is essentially by chemicals following a monitoring system using pheromone traps.
Citrus leaf miner (Phyllocnistis citrella) causes serious damage to new leaves and is of particular concern in the nursery and in young plantings (less than 5 years of age). At these stages, trees receive specific chemical treatments. In general, in older orchards, the Spring flush, which constitutes the most important vegetative growth component, generally escapes insect damage but the Summer and Fall growths are significantly impaired by the insect. However, because Spring growth is heavy and trees provides satisfactory yields, no specific control is done to mature trees.
The mites Panonychus citri (the red mite) and Tetranychus sp. are prevalent from June to November and their abundance is temperature-dependent. The predatory mite, Euseius stipulatus can have a depressing effect on the population of the pest mite provided that chemical use is avoided or at least minimized and properly used.
The most common tree pathogens are Phytophthora gummosis but dry root rot is also becoming an important fungal disease on ?Nour? clementine trees grafted on citrange rootstocks. Brown rot due to to the fungus Phytophthora can develop in the field in years of frequent rains particularly on fruits of the loose-skinned cultivars. Brown rot can also cause significant damage on other cultivars particularly on fruits located in the lower part of the tree canopy and for trees that have quite low ?skirts? and heavy foliage. Green and blue molds due to Penicillium develop mostly postharvest. Sour rot due to Geotrichum candidum develops mostly postharvest on degreened fruit and can cause severe damage to fruit not only before packing but also afterward if fruit sorting is not properly done in the packing line.
The scaly bark type of Psorosis is the most common viral disease, particularly on old orange trees. Exocortis symptoms are rare but occur on trees grafted on citrange rootstocks but either made by the grower using unhealthy budwood or purchased from an unreliable nursery. Stubborn disease occurs on trees grown in inland hot areas.

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Harvest and postharvest

Fruit harvest is entirely done by hand (Fig. 7) with maximum care to avoid fruit bruising which may lead to decay during storage or during transit from the packinghouse to the destination market.



Fig. 7. Harvest of "Valencia oranges.

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Because of high day temperatures in the Autumn, early varieties such as clementines can reach internal maturation while external skin color is still green. Ethylene degreening (5 ppm) is performed on the fruit for color development. Immediately after harvest, fruits destined to degreening receive a postharvest 2,4-D treatment at low concentration (4-8ppm) to keep the button (calyx) green and inhibit its abscission. Green calyx is seen by the consumer as a sign of freshness.
Virtually 90% of Moroccan citrus transits through packinghouses (Fig. 8). Annual discards range from 30 to 50% and vary with variety and season of harvest. In clementines for example, discards are usually higher after rains due to damage done to the rind or during years of heavy crop with a large proportion of small size fruit. For ?Valencia? orange, discards are higher due to regreening of the fruit skin as a result of rising spring temperatures.
In the packinghouse, fruit is washed, then waxed to improve fruit shine and reduce weight loss, and treated with fungicides to inhibit development of decay postharvest. After sizing, fruit is packaged in either cardboard or wooden boxes of various weights according to the specifications given by the destination market.
Fruit is shipped almost totally by boat and the duration of transit takes one to three weeks depending on the distance to destination markets.



Fig.8. View of a citrus packingghouse.

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Estos contenidos están realizados para Ud. por © Ediciones de Horticultura, S.L. - 2003
Queda prohibida la reproducción total o parcial de estos contenidos sin autorización previa.

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SUMARIO

Economic importance and destination of the production

Production areas

Varieties, rootstocks and period of production

Propagation, rootstocks and planting densities

Pruning and fruiting

Pests and diseases

Harvest and postharvest