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Agricultural Science
Crop Description and Climate
Pineapple (Ananas comosus) is a perennial crop grown for its fruits and used as a fresh and processed product. World production is about 13.7 million tons fresh fruit.(FAOSTAT, 2001 from FAO source).
The origin of the pineapple is still uncertain but the Parana-Paraguay Basin has been considered as a possible area. For good growth pineapple requires mean daily temperatures of 22 to 26°C with an optimum of 23 to 24°C. Mean daily maximum and minimum temperatures of 30 and 20°C respectively for the whole growing period are considered optimum. Temperatures below or above this range affect fruit quality or the acid and sugar content.
The crop is grown between 31°N and 34°S, primarily in regions with high relative humidity. A combination of optimum temperature and high humidity results in soft, large leaves and juicy fruits, low in acid content. Fruits ripening in periods with cool temperatures and low radiation levels, e.g. in winter or at high altitudes, are of inferior quality because of poor shape for canning. Requirements for canning are: a cylindrical shape, fruit eyes of a relatively shallow surface and a small fruit core in relation to the fruit.
Pineapple can grow on a wide range of soils but a sandy loam texture is preferred. Optimum soil pH is 4.5 to 6.5. The soil should have a low lime content. The crop is sensitive to waterlogging and therefore requires a well-drained soil with good aeration. For high production the fertilizer needs are 230 to 300 kg/ha N, 45 to 65 kg/ha P and 110 to 220 kg/ha K.
Pineapple is usually grown in double rows on raised beds. With a spacing of 0.6 x 0.3m in beds 0.75 to 0.90m apart, plant population is about 50000 per ha. Shading is sometimes used where temperatures are high and radiation intense to protect the crop from scorching. The crop is multiplied using slips, crowns and shoots or suckers, but in comparison with using suckers as planting material, the period from planting to harvest is about 20 percent longer when slips are used, and about 35 percent longer when crowns are used. Use of different planting material allows a manipulation of the crop growing period and particularly in selection of the time of harvest when climatic conditions are favourable for high quality fruits. Normally the plant crop is followed by one ratoon crop, but when climatic conditions are favourable, the crop will continue to bear fruits but quality rapidly declines after the first ratoon. However, in warm tropical climates, e.g. at low altitudes near the equator, no ratoon crop is possible because suckers do not develop. The period from planting to harvest of the plant crop is 1 to 2 years and of the ratoon crop 9 months to 1.5 years depending on planting material and climate.
Water Uptake
The rooting system of pineapple is shallow and sparse. In deep soils, maximum root depth may extend up to 1m but roots are generally concentrated in the first 0.3 to 0.6 m, from which normally 100 percent of the water is extracted (D = 0.3-0.6 m). Under conditions when maximum evapotranspiration is 5 to 6 mm/day, water uptake starts to be reduced when about 50 percent of the available soil water has been depleted (p = 0.5).
Irrigation Scheduling
Adequate water supply is essential particularly during the vegetative period. The interval of application can be based on the prevailing rate of maximum evapotranspiration (ETm) and the fraction (p) of the total available soil water. Where rainfall is small and irrigation water supply is restricted, irrigation scheduling should be based on avoiding water deficits during the period of vegetative growth (1). Supply of water can be restricted during the period of ripening (4) whereas some water savings can be made by allowing higher depletion levels up to 75 percent during flowering (2). During the month prior to harvest irrigation is discontinued. The method of irrigation is mostly by sprinkler.
Yield
The fruit contains about 80 to 85 percent water and 10 to 14 percent sugar. Irrigation has an effect on the sugar/acid ratio, particularly in the period prior to harvest when frequent high irrigation decreases the sugar content. The infestation by soil-borne fungus diseases is increased. Under commercial production, weight per fruit is about 1. 5 to 1.8 kg, and total yield between 75 and 90 ton/ha fresh fruit. The water utilization efficiency for harvested yield (Ey) for fresh fruit is about 5 to 10 kg/m3for the plant crop and 8 to 12 kg/m3for the first ratoon crop.
Pests and diseases control
Pineapples rarely suffer from pests and diseases when good growth conditions have been cared for. The following diseases and pests occur especially in systems which lack diversification.
1. Pineapple Mealybug Wilt-associated closterovirus (PMWaV)
••>Infected plants become yellowish-red to bright red at the leaf tips, this coloration spreading down the leaf with time. •Soon other leaves turn colour and also show signs of wilting. •The inner heart leaves remain normal. •Severely infected plants become stunted and produce small, under-grade and immature fruits
•The first effect of the disease usually appears in the roots, which stop growing, collapse and then rot; this results in leaves symptoms similar to the effect of drought.
•The disease is probably introduced in planting material, which may not show obvious disease symptoms. Once established, it is spread by mealybugs, sedentary insects, which are moved from plant to plant by attendant ants.
Management:
Use planting material from wilt-free areas. Heating pineapple crowns in a large water bath at 50°C for 30 minutes enables 100% plant survival and renders 100% of the plants free of pineapple wilt-associated virus. Growth of the heat-treated plants is more rapid than in non-heat-treated plants. Plant resistant varieties if available. Some varieties of pineapple are more resistant to the virus than others, the variety Cayenne (and 'Masmerah') being highly susceptible. ‘Spanish’ shows some resistance.
2. Pineapple mealybug (Dysmicoccus brevipes)
The mealybugs are oval, pink in color, up to 3 mm long, covered with a whitish waxy secretion, which develops into waxy filaments around the body.
•This mealybug is the most serious pest of pineapples, because it is a vector of the Mealybug or Pineapple Wilt Virus.
•The mealybug is common on the roots of pineapple and large colonies develop on the stems just above ground level.
•The mealybugs may spread upwards to feed in the floral cavities, on both small and mature fruit, and on the crown leaves.
•Heavy infestations are conspicuous because of the white waxy adults, which often occur at the growing points, around the stem nodes, on the undersides of leaves, on the fruit and on the roots.
Management:
Control ants to give a chance to natural enemies to keep mealybugs under control. See also what to do by pineapple wilt virus, specified above.
3Yellow spot virus: Syptoms:
The yellow spot virus has been shown to be identical to up the tomato spotted wilt virus. It infects over a 100 species of plants including peppers, tomato, tobacco, eggplant, potato, broad bean, spinach, chicory and peas. A number of wild plants, including some common weeds such as the black jack (Bidens pilosa) and Datura stramonium, are also host of this virus. Thrips are vectors of this virus.
When host plants of the virus are grown near to pineapple plants, the incidence of the yellow spot virus is considerable enhanced due to thrips migrating into the pineapple field. Wind carries thrips long distances and thus also plays an important role in the transmission of the virus.
Symptoms i
In the fruit is a blackened, dry cavity in the side of the fruit due to one or more "eyes" having died. Thrips feeding on the crown of fruits results in concentric ring patterns developing on crown leave
Management: Control weeds in and around pineapple fields. This is very important for disease control because the presence of certain weeds leads to increased number of thrips. Cut off the fruits showing early symptoms of infection. This will prevent the spread of infections into the fruits. •Where this disease is a problem avoid planting near host plants of the thrips and the virus. •Even if thrips are not strongly inclined to migrate from their favored host plants, they will do so if disturbed, for instance by human passing, animals or machinery. Control thrips. 4.Thrips (Thrips tabaci and Frankliniella schultzei) Symptoms:
The blossom thrips feeds mainly on flowers and its feeding results in the development of "dead-eye" in the fruit. Thrips feeding on the crown of fruits results in concentric ring patterns developing on crown leaves.
Management:
•Control weeds in and around pineapple as certain weeds leads to increased number of thrips. Remove heavily infested plant material. •Control thrips in the early stages, in particular immature thrips; adult thrips are unable to pick the virus from infected plants. Once the immature thrips are infected with the virus they remain vectors for the rest of their lives. •Spray with insecticide (Lambda-Cyhalothrin,... (1ml/1L of water). Also a garlic bulb extract can be sprayed thoroughly on the whole plant, preferably early in the morning. Spraying should be particularly directed to the neck area of the plant for good penetration into the plant.
5. Pineapple top and root rot
The leaf edges curve back and leaves are easily pulled out from the plant. Internally, the stem and leaf bases become soft, rotten and have an unpleasant smell. The growing point of the stem has a cheese-like appearance. It is common in young plants of 3-8 months. Splashing rain, irrigation water and biting insects act as agents to spread disease.
Management:
•Do not plant pineapples in soils prone to waterlogging.
•Ensure good drainage.
•Improve soil by selective fruit rotations and application of organic compost material.
•Avoid overhead irrigation.
•Control insect pests.
•Planting materials can be dipped in copper fungicides before planting or use resistant plants.
•Fungicides can be used to control any fungal complications.
6. Black rot of pineapple (Ceratocystis paradoxa)
•White leaf spots are yellow to brown and several centimeters long. •Later they dry to become papery and straw colored. •Black rot is a post-harvest disease occurring only on injured pineapple fruit. •Only freshly cut or injured tissue is infected, and a soft black rot with dark colored mycelium develops Management:
•Use crop management practices that promote germination and rooting. •In disease prone areas, if possible, plant varieties that are quick to germinate. Varieties that are slow to germinate should be treated in hot water (50°C for two hours). •Avoid extremely wet or dry soil conditions. •Do not plant freshly cut pineapples unless dried out To prevent the spread of the pathogen, avoid wounds to tissue and remove infected pineapple plants. •Improve soil drainage and avoid planting during wet weather.
When will it be harvested
When the fruit is one-third or more yellow, you can go ahead and harvest it. You can also harvest pineapple when it is in the late mature green phase, or when it is full-sized. You can then ripen the pineapple at room temp. Don’t refrigerate it until it is completely ripe! Refrigerating an unripe pineapple can ruin the fruit. To harvest the pineapple, simply cut it from the plant with a sharp kitchen knife where the pineapple joins the stalk. Then either leave it to further ripen at room temp if need be, refrigerate the fruit if completely ripe, or, ideally, devour immediately!
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