Dates

Description

The date palm, Phoenix dactylifera, is an erect palm tree in the family Arecaceae grown for its edible fruit, the date. The trunk of the tree is covered in upward-pointing, overlapping, woody leaf bases and terminates in a crown of 20–30 leaves. The leaves are feather-like with spiny petioles and thick midrib. The leaf blades are pinnately divided and are blue-green in color. The uppermost leaves of the crown stand more erect while the lower ones droop and recurve toward the trunk. The tree produces small, fragrant cream-white flowers and the inflorescence may possess as many as 10,000 flowers. The fruits are produced in clusters and are oblong to ovoid berries with single stones and red-brown flesh. Date palms can grow to a height of 30 m (98 ft) and can live for up to 150 years, although they are usually replaced in commercial plantations when their productivity begins to decline. The date palm is believed to originate from Western Asia.


Uses

Dates are consumed as a fresh or dry fruit. They are considered a staple in the deserts of North Africa and the Middle East. The fruit may also be used to make juice concentrates, fermented products (e.g. wines) or pastes for use in baking and confection.


Propagation


Basic requirements
Date palms grow best in semi-arid climates close to water bodies such as rivers or oases, with an annual average temperature of 12–27°C (53.6–80.6°F) in regions where there is a long hot summer and mild winter. A mean temperature of 21–30°C (69.8–86°F) for at least one month is necessary for fruit production in addition to a period of no rainfall during flowering to prevent damage to the flowers. Date palms grow well in a wide range of soils provided they are well-draining, have a pH between 5.2 and 8 and are in close proximity to a body of water. Fruit production is highest when grown in sandy loams.

Propagation
Date palms for commercial cultivation are usually propagated from suckers removed from the base of mature trees to allows desirable characteristics to be maintained. The suckers should be between 3 and 6 years old and are separated from the mother along with some root. Separating of suckers is usually carried out in late summer of Fall. The newly detached suckers are planted to a depth of 80 cm (31.5 in) leaving 9–10 m (30–33 ft) between plants. The newly planted suckers should be watered daily for the first week to aid in establishment and once weekly thereafter.

Pollination
Date palms are protandric which means that the male flowers are produced before the females. In order for successful pollination to be guaranteed, commercial date palms are pollinated by hand or with the use of machinery. Hand pollination is achieved by cutting the male inflorescence from the palm and joining strands to the female inflorescence. Alternatively, the pollen is extracted and mixed with flour and the mixture is then applied mechanically to the female flowers. Mechanical pollination is conducted with the aid of a small insecticide duster known as a ‘puffer’.

General care and maintenance
Date development is aided by removing dead leaves and thorns from the trees, thinning of fruit and bunches and also the removal of bunches if the number per palm is too high. Allowing palms to over produce will reduce yield the following year. Each of these practices also aims to maximize fruit size and promote regular fruit production. When bunches begin to develop, they are pulled down and tied to lower leaves in order to protect them from damage from wind. Dates require dry and hot conditions to ripen in combination with the large amount of irrigation of the soil.

Harvesting
Harvesting of ripe dates requires reaching the top of the palm tree. This is achieved through the use of ladders which may be permanently fixed to the tree or through the use of machinery that can raise the worker on a platform. In the Northern Hemisphere, harvest begins at the end of the summer into early Fall and ends around November depending on the variety. Some varieties continue to be harvested after the onset of the rainy season but rain can damage the fruit and reduce its quality so the fruits are usually protected with the use of waxed paper or nylon sleeves.


References

CABI Crop Protection Compendium. (2014). Phoenix dactylifera datasheet. Available at: http://www.cabi.org/cpc/datasheet/40698. [Accessed 20 November 14]. Paid subscription required.

Elliott, M. L., Broschat, T. K., Uchida, J. Y. & Simone, G. W. (2004). Compendium of Ornamental Palm Disease and Disorders. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.

Morton, J. (1987). Date. In Fruits of Warm Climates. Morton, J. F. Echo Point Books & Media. Available at: http://www.hort.purdue.edu/newcrop/mo.... [Accessed 20 November 14]. Free to access.

Zaid, A. (2002). Date Palm Cultivation. Food and Agricultural Organization of the United Nations (FAO). Available at: http://www.fao.org/docrep/006/y4360e/.... [Accessed 20 November 14]. Free to access.


Common Pests and Diseases

Bayoud disease
Fusarium oxysporum

Symptoms
Leaflets of mature leaves becoming chlorotic at the base on one side; leaf death progressively to the leaf tip; brown or white lesions on underside of leaves
Cause
Fungus
Comments
Soil-borne disease; currently restricted to Morocco and Algeria where it can be devastating; the popularity of susceptible cultivars means it has a massive potential to continue to spread
Management
Cultural control is not recommended for the control of the disease as conditions which favor high yield of dates also favors growth of the fungus; if disease is confirmed then infected tree should be uprooted and burned to prevent spread; soil should be treated with methyl bromide or chloropicrin and the area closed off

Black scorch disease
Ceratocystis paradoxa

Symptoms
Dark brown-black, hard lesions on leaves; foliage with scorched appearance
Cause
Fungus
Comments
Palms may recover from disease; fungi can enter through pruning wounds
Management
Prune out infected fronds, leaf bases and inflorescenses and burn the material immediately; pruning wounds should be protected by spraying with Bordeaux mixture

Diplodia disease
Diplodia phoenicum

Symptoms
Death of suckers either while still attached to mother or after planting
Cause
Fungus
Comments
Fungus usually enters through cutting or pruning wounds
Management
Disinfect all tools and equipment regularly; protect pruning wounds and cuts with Bordeaux mixture or other appropriate copper based fungicides

Graphiola leaf spot
Graphiola phoenicis

Symptoms
Small spots on both sides of leaves; yellow spore masses on leaves; black crater-like lesions on leaves
Cause
Fungus
Comments
Disease emergence favored by high humidity
Management
Infected leaves should be pruned out and destroyed; disease can be controlled by sprays of Bordeaux mixture or other appropriate broad spectrum fungicide

Khamedj disease
Mauginiella scattae

Symptoms
Brown or rust colored area on unopened spathes; partial or complete distruction of flowers
Cause
Fungus
Comments
Disease emergence favored by hot, humid conditions in neglected plantations
Management
Good sanitation practices and maintenance of the plantation helps to control the disease; infected spathes and inflorescences should be removed and burned; diseased palms should be treated with Bordeaux mixture or appropriate copper based fungicide after harvest and approximately 1 month before emergence of spathes

Parlatoria date scale
Parlatoria blanchardi

Symptoms
Discolored areas on leaflets where insects are feeding; leaflets turning yellow and fronds dying; discolored fruits; insect is a circular-oval scale
Cause
Insect
Comments
Insect is a serious pest in Algeria, Kuwait, Libya, Mauritania, Morocco and Tunisia; attacks by the scale are very serious on young palms
Management
Population of natural enemies coupled with pruning of palms usually keeps scales under control; mineral based oils are effective against nymphs

Coconut rhinoceros beetle
Oryctes rhinoceros

Symptoms
V-shaped cuts in palm fronds or holes in leaf midribs caused by beetles boring into crown to feed; adult insect is a large black beetle with a curved spine on its head; larvae are creamy white grubs with brown heads and 3 sets of prolegs at the anterior (head) end
Cause
Insect
Comments
Beetles are nocturnal and fly at night; also a damaging pest of oil palm
Management
Destroy any decaying logs in plantation by chopping and burning to kill any larvae that may be inside; remove any dead trees from plantation and destroy by burning; plant a cover crop to deter egg laying by females as they do not lay eggs in areas covered by vegetation; hooked wire can be used to extract larvae that are boring into young crowns

Lethal yellowing
Lethal yellowing phytoplasma

Symptoms
Fronds drying out and turning gray-brown; growing tip rotting and turning into a slimy mass with foul smell; crown collapses from trunk leaving a naked trunk
Cause
Phytoplasma
Comments
Disease is transmitted by planthoppers
Management
Disease severity can be reducced by injecting the antibiotic oxytetracycline HCl into the trunk; antibiotics can also be administered as a protective measure if the disease is known to be in the area; control of the disease long term relies on planting resistant or tolerant varieties