Pineapple

Description

Pineapple, Ananas comosus, is an herbaceous biennial or perennial plant in the family Bromeliaceae grown for its edible fruit. The pineapple plant has a short stout stem and a rosette of sword-shaped leaves with needle-like tips. The leaves are waxy, have upturned spines on the margins and may be soild green or striped with red, white or cream. When the plant flowers, the stem begins to elongate and produces a flower head of small purple or red flowers, each with a pointed bract. The stem continues to elongate and sets down a tuft of of short leaves called a 'crown'. Individual fruits develop from the flowers and fuse to form one large cylindrical fruit topped by the crown. This fruit, known as a pineapple, has a tough rind made up of hexagonal units and a fibrous, juicy flesh which may be yellow to white in color. Pineapple may reach 1.5–1.8 m (5–6 ft) in height and some varieties can grow for in excess of 20 years. Pineapple originates from the tropical regions of the Americas.


Uses

Pineapple fruit is commonly eaten fresh or it may be cooked in a variety of dishes. Pineapple may also be canned or used to produce juice.


Propagation


Basic requirements
Pineapple is a tropical plant and grows best in temperatures between 23–32°C (73.4–89.6°F). The plant can tolerate colder temperatures for short periods but will be killed by frosts. Pineapple will grow optimally in well-draining sandy loam which is rich in organic matter. The optimum pH for pineapple growth is between 4.5–6.5. Established pineapple plants are tolerant of drought but will not tolerate waterlogged soil which quickly leads to root rot.

Propagation
Pineapple is propagated from crowns, slips or suckers, with slips or suckers being the preferred method for commercial growers. Pineapple suckers arise from leaf axils, while slips grow from the stalk below the fruit. These are cut from the parent plant and used to produce new plantings. The cuttings are usually cured for a day or two prior to planting by sitting them in the shade. Pineapple plantings are normally set out in double rows with the material staggered 25–30 cm (10–12 in) apart within the double row and allowing a further 60 cm (2 ft) between double rows.

General care and maintenance
Pineapples require supplemental irrigation during dry spells for optimum production. Mulching around the plants will help to conserve soil moisture. Ratooning may also be utilized as a means of encouraging growth. After the first crop of fruit, ratooning the plants will result in new fruit within 18 months. This process may be repeated a second or third time but then the crop will be rotated to prevent build up of disease. Removing suckers and slips from developing plants helps the plant to focus energy on growing the fruit and leads to larger fruit that develops quicker. Pineapples benefit from the application of additional nitrogen and potassium. Application rates depend largely on the type of soil the plants are growing in. Generally, little fertilizer is required during the first few months following planting but requirements increase rapidly in the period leading up to flower development. Fertilizers are usually applied as foliar sprays.

Harvesting
Pineapples are ready to harvest when at least one third of the fruit rind has turned from green to yellow. Fruits are harvested by hand by cutting the crown and peduncle from the plant. The fruit will continue to ripen off of the plant.



References

Bartholomew, D. P., Rohrbach, K. G. & Evans, D. O. (2002). Pineapple cultivation in Hawaii. University of Hawaii Cooperative Extension Service. Available at: http://www.ctahr.hawaii.edu/oc/freepu.... [Accessed 27 March 15]. Free to access.

CABI Crop Protection Compendium. (2013). Ananas comosus (pineapple) datasheet. Available at: http://www.cabi.org/cpc/datasheet/5392. [Accessed 27 March 15]. Paid subscription required.

Crane, J. H. (2013). pineapple growing in the Florida home landscape. Available at: http://edis.ifas.ufl.edu/mg055. [Accessed 27 March 15]. Free to access.

Ploetz, R. C., Zentmyer, G. A., Nishijima, W. T., Rohrbach, K. G. & Ohr, H. D. (eds) (1994). Compendium of Tropical Fruit Diseases. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.


Common Pests and Diseases

Marbling
Acetobacter spp.
Erwinia herbicola

Symptoms
Yellow to red or very dark brown discoloration of fruit flesh; infected tissues develop a granular texture with woody consistency and speckled color; single or multiple fruitlets may be affected; vascular system may appear speckled right down to core of fruit; symptoms develop during the last month of fruit maturation
Cause
Bacteria
Comments
Emergence of the disease is favored by warm, wet weather
Management
There are currently no methods of controlling the disease; the pineapple variety Smooth Cayenne appears to be moderately resistant to the disease

Bacterial heart rot and fruit collapse
Erwinia chrysanthemi

Symptoms
Water-soaked lesions on the white basal sections of leaves in the central whorl which may spread to all leaves in the central whorl; midportions of leaves become olive green in color with a bloated appearance; infected fruits exude juices and the shell becomes olive green; cavities form within the fruit
Cause
Bacterium
Comments
Disease is thought to be spread from the juices of infected fruits; bacteria in the juice can enter leaves through wounds; ants acts as vectors for the bacteria
Management
Remove and destroy infected fruits; avoid the use of infected crowns for seed material to prevent spread of the disease; planting to avoid flowering when adjacent field is fruiting can reduce disease development; use of miticides and control of ants can significantly reduce disease incidence

Butt rot, Black rot & White leaf spot
Chalara paradoxa

Symptoms
Soft black rot which begins at the area where the seed piece detaches from the mother plant; entire seed piece may be rotted; black rot of fruit causes a soft, watery rot which darkens with time; small brown, wet spots develop on leaves; leaf spots enlarge and turn gray-brown with light brown margins
Cause
Fungus
Comments
Fungus survives in soil and pineapple residue; infects plants through fresh wounds
Management
Seed material should be stored on mother plants during dry weather and with good air circulation; freshly removed seed material should be dipped in an appropriate fungicide within 12 hours of removal from the mother plant; avoiding bruising and wounding of fruit during harvest helps to reduce black rot; harvested fruit should be dipped in an appropriate fungicide within 6-12 hours of harvest to prevent disease development during shipping

Mealybugs (Pineapple mealybug)
Dysmicoccus brevipes

Symptoms
Flattened oval to round disc-like insect covered in waxy substance on tree branches; insects attract ants which may also be present; insect colony may also be associated with growth of sooty mold due to fungal colonization of sugary honeydew excreted by the insect; plants may show symptoms of mealybug wilt (see entry)
Cause
Insect
Comments
Insects have a wide host range; often tended by ants which farm them for their sugary honeydew secretions; transmit mealybug wilt in pineapple
Management
Mealybugs can potentially be controlled by natural enemies such as lady beetles; ant populations which tend the mealybugs should be treated with an appropriate insecticide

Phytophthora heart and root rot
Phytophthora spp.

Symptoms
Young leaves failing to elongate and turning chlorotic; heart leaves wilting and turning brown; terminal whorl can be easily pulled from mother plant; water-soaked tissue at base of leaves; foul smell; leaves may be turning red and yellow with necrotic leaf margins and leaf tips; plants can easily be pulled out of the ground; fruits color prematurely
Cause
Oomycete
Comments
Fungi can survive in soil and plant debris for many years
Management
Planting in raised beds helps to drain the soil and reduces incidence of the disease; mulch from pineapple debris should be avoided; pre-planting dips and foliar applications of Fosetyl Al are very effective at controlling the disease

Mealybug wilt
Pineapple wilt virus (PWV)

Symptoms
Leaves turning red; tips of leaves become withered and turn brown; plants can be easily removed from the soil
Cause
Virus
Comments
Virus is transmitted by mealybugs; ants protect mealybug populations from predators and parasites and can allow mealybugs populations to reach very damaging levels if left uncontrolled
Management
Ants should be controlled with an appropriate insecticide