Introduction to Plantains and their Environment

Plantains (Musa spp., AAB genome) are plants producing fruits that remain starchy at maturity (Marriot and Lancaster, 1983; Robinson, 1996) and need processing before consumption. Plantain production in Africa is estimated at more than 50% of worldwide production (FAO, 1990). The majority (82%) of plantains in Africa are produced in the area stretching from the lowlands of Guinea and Liberia to the central basin of the Democratic Republic of Congo. West and Central Africa contribute 61 and 21%, respectively (FAO, 1986). It is estimatedthat about 70 million people in West and Central Africa derive more than 25% of their carbohydrates from plantains, making them one of the most important sources of food energy throughout the African lowland humid forest zone (Swennen, 1990).

Nigeria is one of the largest plantain producing countries in the world (FAO,2006). Despite its prominence, Nigeria does not feature among plantain exporting nations because it produces more for local consumption than for export. National per capita consumption figures show its importance relative to other starch staples (FAO, 1986).

However, these figures do not show regional reliance, which is often very important for highly perishable crops that are usually consumed in or near areas of production. The consumption of plantain has risen tremendously in Nigeria in recent years because of the rapidly increasing urbanization and the great demand for easy and convenient foods by the non-farming urban populations. Besides being the staple for many people 2in more humid regions, plantain is a delicacy and favored snack for people even in other ecologies. A growing industry, mainly plantain chips, is believed to be responsible for the high demand being experienced now in the country. This study reviews the trend of plantain production, its problems and prospects in Nigeria in the last two decades.

  1. Morphology

Bearing plants consist of:

(a) The Bunch or inflorescence: Composed of many flowers, the bunch emerges between the leaves and is attached to the plant by a rachis or fruit stalk. The many protuberances on the rachis are called glomerules. Each glomerule bears a group of flowers, also called a hand. Edible fruit (or fingers) develop from female flowers located at the first 10 glomerules of the bunch. Neutral flowers (also called hermaphrodite or intermediate flowers) appear next but do not develop into fruit as their ovaries cannot swell to form pulp. The purple bud at the end of the bunch is called the “male bud” and consists of bracts covering groups of so-called male flowers. This male bud may be absent or present when the bunch reaches maturity.

(b) ThePseudo stem with foliage leaves: The cylindrical structure rising from the soil and carrying the foliage is not a stem in the true sense. It is a “false” stem or pseudostem because the growing tip (or meristem) of the plant remains near soil level. As the false stem consists of overlapping leaf sheaths, plantains are like giant herbs and not like trees. The leaf sheaths render support to the rachis of the mother plant. Young suckers (shoots from the main plant which can develop into bearing plants) have narrow, lanceolated leaves which are called scales and are easily distinguishable from the large foliage leaves.

(c) The Underground corm with suckers and roots: The corm, sometimes wrongly called a bulb, is the true stem of the plant.

Numerous roots emerge from the corm, most of which grow horizontally at a depth of 0 to 15 cm. Roots are whitish if young and healthy and become brown with age. If infested by nematodes, they become brown or even black and/or show protuberances.

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The growing tip (or meristem) at the top of ·the corm continuously forms new leaves and later becomes the inflorescence. The corm produces many branches, called suckers, and the whole unit is often referred to as the “mat” or “stool”. After the plant crop has been harvested, the mother plant is cut down and the suckers are thinned. Although all suckers are followers or daughter plants, the cultivator selects one (the ratoon) to continue the next cycle of production. The second harvest from the plantain mat is called the first ratoon crop. The third harvest is the second ratoon crop, and so on.

  1. Cultivars

At least 116 plantain cultivars have been identified in West and Central Africa. Plant size and bunch type are the most important characteristics for production purposes.

Plant size depends on the number of leaves produced before flowering: giant more than 38 foliage leaves; medium between 32 and 38 foliage leaves; small fewer than 32 foliage leaves. When the plantains flower, leaf production has ended.

  1. Sources of planting material

Several types of conventional planting material exist:

Peeper:a small sucker emerging from the soil;

Sword sucker:a large sucker with lanceolated leaves, the best conventional planting material;

Maiden sucker:a large sucker with foliage leaves;

Bits:pieces of a chopped corm.

A new and most promising planting material consists of in-vitro plants which are small maiden suckers produced from meristem culture.

Planting material can be collected from:

(a) An existing field, preferably an old field which is becoming unproductive. Otherwise damage to the roots may be caused when the suckers are being dug out and many mother plants may later tip over.

(b) A multiplication plot, which is planted only for the production of suckers and not to produce bunches. Plant density (2 m x 2 m) is much higher than in production fields and suckers are obtained by either decapitation or false decapitation. Both methods consist of removing the growing point. In the first method, the pseudo-stem is removed to get to the growing point. Only a small hole or window is cut for the second method.

The foliage can remain active for up to 3 months after the removal of the meristem by the second method.

(c) A tissue culture laboratory, where in vitro plants which look like small maiden suckers are produced from meristems. In-vitro plants are healthy, vigorous, and free from pests and diseases (figure 4) and have a great future.

  1. Climate

Plantains, like other bananas. Require a hot and humid environment. Ideally, the average air temperature should be about 30°C and rainfall at least 100 mm per month. Rainfall should be well distributed throughout the year and dry seasons should be as short as possible. Irrigation is not suitable nor economically worthwhile for plantains grown by the family farmer but may become necessary when larger fields are cultivated in areas with a long dry season.

  1. Mulch

Organic matter is essential for plantain cultivation. External sources of mulch can consist of elephant grass (Pennisetumpurpureum), which is rich in potassium, or cassava peelings, wood shavings, palm bunch refuse, dried weeds, kitchen refuse, and so on. Collecting and transporting mulch are expensive in time and labor. The most convenient source consists of plants growing inside the plantain fields if they produce a great deal of organic matter without competing with the plantains.

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Suitable mulch material can be obtained from trees which were slashed when the fields were cleared and which are growing again; or from a deep-rooted legume shrub called Flemingiacongesta or F. macrophylla. F. congesta is seed drilled in the middle of the 3 m plantain alley. It can be difficult to establish, but from the second year onwards it grows vigorously. It can reach a height of approximately 2.5 to 3 m if left unpruned, but in the field it is cut back 4 times a year to a height of about 1.5 m.

The pruning’s are spread over the soil. Flemingia is not fertilized as it benefits from fixed nitrogen and leached fertilizers applied to the plantains. Grass growing between the plantains is not suitable as a mulch source because it competes with the plantains.

  1. Fertilizer

The plantain crop always benefits from the use of fertilizer (table 1). The yield from fertilized plants can be up to 10 times higher than that from unfertilized plants. The amount of fertilizer needed depends on soil fertility and soil type. General recommendations cannot be made as these should be based on soil or leaf analysis and the results of fertilizer experiments.

Since potassium and nitrogen are easily leached, they should always be applied at regular intervals (split applications) during the growing (rainy) season. Other important nutrients are phosphate, calcium and magnesium which are provided in one application. In some exceptional cases, micro-nutrients (for example, zinc or sulfur) have to be applied.

Control Fertilizer Mulch Mulch + fertilizer
Plant crop 0.6 11.9 14.1 18.8
First ratoon 0.6 2.8 10.2 10.4

 

  1. 550 kg of potassium oxide and 300 kg of nitrogen per hectare
  2. 80 tons per hectare of Pennisetumpurpureum (elephant grass)
  3. Weed control

Weeds can be hand-pulled or chemically controlled. Paraquat and simazine are appropriate herbicides since they control the weeds without affecting the plantains, unless leaves are accidentally sprayed. Glyphosate, diuron and gramuron are not recommended as they can be phytotoxic to plantains.

  1. Disease and pest control

Black sigatoka is the major disease attacking plantains; nematodes and stemborers are the major pests.

Black sigatoka is a leaf spot disease caused by the fungus Mycosphaerel/afijiensis. All known plantain cultivars are susceptible to this wind-borne fungus. Leaves first show yellow spots which later turn brown and black. Ultimately the leaf tissue becomes necrotic and dies. In this way entire leaves become nonfunctional and in many cases, bearing plants are left with hardly any green leaves at maturity. Photosynthesis is reduced and small bunches (sometimes with undeveloped fingers) are produced. Yield losses are estimated at between 30 and 50 percent.

Black sigatoka can be controlled with aerial applications of fungicides belonging to the groups of the benomyl, benzimi- dazoles, chlorothalonils, dithiocarbamates, flusilazoles, imazaliles, imidazoles, methylthiophanates, nuarimols, pro- chloraz, propiconazoles, triazoles and tridemorph, or soil- applied fungicides such as triadimefon and triadimenol. In any case, at least two types of fungicide should be used alternately to prevent the fungus from developing resistance to the active ingredient.

Plantain cultivars resistant to black sigatoka provide the only effective means of control since the fungicides are very expensive and can pose health hazards when applied in backyards. Breeding for resistance began at the one station of the International Institute of Tropical Agriculture (IITA) in Nigeria during 1988. For the time being, cooking bananas (“Fougamou

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1 “, “Bom”, “GiaHui”, “Foulah 4” and “Nzizi”) are available from IITA as a substitute for plantain. These varieties are resistant to black sigatoka and can be prepared and consumed in the same ways as plantains.

Nematodes are minute worms which live in the soil and infest plant roots. Several types of nematodes can extensively damage the plantain root system if the land was previously cropped with plantains or if they were introduced with infected planting material. Nematodes impair the transport of nutrients and water to the main stem, causing a reduction in yield and weakening of the plant. As a result, many plants may be lost through tip-over whenever winds become strong.

Nematodes can be controlled by applying nematicides in a circle, 25 cm in diameter, around the plant.

Some of these nematicides are:

Nematicides Rate per plant (grams) No. of applications per year
Isazophos 2.5 a.i. 3
Carbofuran 4.0 a.i. 3
Ethoprophos 4.5 a.i. 3
Phenamiphos 3.0 a.i. 3

a.i. = active ingredient

As carbofuran is effectively degraded by microorganisms, it should be used alternately with other nematicides.

The stem borer or banana weevil Cosmopolites sordid which usually lays its eggs near the corm of the main plant. The larvae attack the underground part of the plant; feeding on the corm and boring channels in it Plants become very weak, especially during the dry season, and tip over. Yield can be drastically reduced.

Stem borers can be controlled by leaving the land under fallow, by the application of coffee husks and by insecticides.

Nematicides Rate per plant (grams) No. of applications per year
Isazophos 2.5 a.i. 3
HCH (50%) 40 c.p. 3
Chlordecone 1 a.i. 2
Isofenphos 1.2 a.i. 3
Aldicarbe 1.5 a.i. 3
Carbofuran 2 a.i 3

c.p = Commercial product a.i. = active ingredient

The cost of insecticides should determine whether they should be used. The use of traps provides an alternative method for controlling banana weevils which is cheap but time-consuming and not as effective as the use of insecticides. Traps are made by cutting pseudo-stems in half longitudinally and laying the pieces cut side down on the soil near the plantains. One trap for every 20 to 30 plants is the current practice. Traps should be inspected daily early in the morning. The adult black weevils are then retrieved from between the soil and the cut surface of the pseudo-stem and killed. Traps remain effective for about 1 or 2 weeks and are renewed at harvest when an ample supply of pieces of pseudo stem is available.

  1. Fallow

A field that becomes unproductive should be left fallow when the plantain mats have been destroyed. Good results can be obtained with the use of kerosene, glyphosate or 2-4 0 but the plantain mats can only be completely destroyed by hand. This ensures that no live material remains to harbor pests and reinfect the field.

To restore fertility, the organic matter in the soil should be raised as high as possible during the fallow period by planting an improved fallow (for example, a leguminous cover crop).

Otherwise the fallow crop can consist of trees which were cut down at planting time and are growing back or of Flemingiacongesta which was grown between the plantain rows as a source of mulch. In addition to restoring fertility, the fallow crop should by itself completely eliminate all kinds of weeds, especially grasses. A grass fallow is not suitable as grass easily grows again and becomes a noxious weed.

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Author: Benadine

A Practical Farmer, An Agric. Consultant, An Author and A Model.

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