Fungal Diseases

Bayoud, a consequence of the fungus Fusarium oxysporum f. sp. Albedinis, is the name given to fusariosis of the date palm, which is found in the soil, and derives from “abiadh” (white in Arabic), given the color that the plants’ leaves take on when attacked by the fungus. Since the end of the 1800s, this devastating disease has mostly struck the Moroccan palms -more and more aggressively for almost a century- destroying over 12 million of the most prestigious species. From there, it extended as far as the Algerian Sahara where 3 million date palms have been attacked, even though the advancement of the disease towards the east and south appears to be arrested, due to the interventions of the Algerian government.
The parasite is particularly insidious inasmuch as it is present in the soil and various host plants (medicinal herbs, henna, etc.) and transmitted from plant to plant through normal irrigation, since it begins in the roots of the data palm.
Although there is no specific cure, methods to prevent and limit the spreading of this fungus are: chemical treatment of the soil (not very effective); digging trenches of approximately 2 meters deep around the infected plants (to prevent spreading from the roots); reduction of irrigation in the hottest months (considering that the fungus needs constant humidity to proliferate); commercial isolation of the areas affected by Bayoud (no part of the infected plant is worked or exported to other regions); selecting varieties of date palms that are resistant to the fungus; mycorrhization of the date palms (a technique used to bio-remediate the soil); the choice of organic fertilizers that limit spreading of fungus; and recently, the use of autochthonous Algerian desert plants, which are poisonous to the parasite.

“Medjnoon” (from the fungus Thielaviopsis paradoxa), also called black scorch, is an occasional disease that strikes the palms groves throughout the world, causing necrosis in various parts of the tree. This disease is controlled by removing the blackened areas and treating them with a fungicide. Similarly, the fungus Mycosphaerella tassiana causes necrosis of the leaves with a typical brown color, without affecting the health of the whole tree.

Diplodia (from the fungus Diplodia phoenicum) is typically caused by lack of disinfestation of the tree.

Graphiola (from the fungus Graphiola phoenicis), or Grafiola leaf spot, occurs following cutting and grafting of the tree, and is one of the most diffuse diseases worldwide, striking palm groves in the more humid areas (particularly in Egypt, Saudi Arabia, and also in Niger and Mauritania). The disease sensibly shortens the lifespan of the trees which is revealed through the slow and progressive appearance of miniscule spots that vary in color from yellow to black. Control measures are intense treatments with fungicides.

“Khamedj” (from the fungus Mauginiella scaetae) is another disease that is diffuse worldwide in the more humid palm groves, and which sensibly reduces the productivity of the palm. The disease is manifested through the appearance of brown rot on the inflorescences, and is spread by the same spores of the flowers. It is controlled by burning the infected parts and disinfecting with fungicides.

Omphalia (from the fungus O. tralucida or O. pigmentate), diffuse in Mauritania, predominately strikes older trees, blocking the growth of new foliage and causing the roots to rot.

Belâat (from the fungus Phytophtora sp ), or bud rot, strikes the palm groves of North Africa causing whitening and death of the new fronds, and then progressively the rest of the plant, releasing a typical acetic odor. The disease is controlled with fungicides.

And lastly, fruit rot (from the fungi Aspergillus niger; Alternaria spp.; Fusarium spp.; Penicillium spp. etc.), which is caused by delay in harvesting the fruit, by an increase in the humidity level, and lack of ventilation in the fruit bunches. It can easily strike between 10% and 50% of the harvest.

Phytoplasmic Diseases

Lethal Yellowing (Candidatus Phytoplasma asteris) is a deadly disease which manifests itself in the date palm with a progressive greyish-brown coloring of the fronds followed by the putrefaction and falling of the crown of the tree, leaving a nude trunk. The stricken palms must be removed and the affected areas must be isolated. Antibiotic treatments exist.

Al Wijam, diffuse in Saudi Arabia, is a lethal disease that manifests itself through slow and reduced growth of the foliage, which is marked by a characteristic yellow line. The leaves die rapidly and the productivity of the tree is suddenly and sensibly reduced.

Brittle leaves disease, or “Maladie des Feuilles Cassantes” in French, is diffuse in Tunisia and Algeria and manifested by clorosis of the fronds whose tips then become brittle.

Unknown Causes of Disease

The so-called “Le Coeur qui penche”, or bending head, is easily recognizable by the fact that the upper part of the palm bends progressively downwards.

“Dry Bone” causes whitening and progressive hardening of the fronds, which indeed resemble bones.

Rhizosi is a lethal disease that causes the fruit to fall with subsequent reddening of the foliage and death of the tree.

Physiological disorders

“Blacknose” is caused by excessive humidity which causes blackening and flaking of the tip of the date’s skin, while “Whitenose”, due to excessive ventilation, causes dryness, hardening and whitening.

Freezing (at temperatures below zero, which is the seasonal rule for desert nights) causes considerable damage to the date palm but can be controlled by irrigating the palm grove in the coldest moments. Lack of, or excess irrigation, just as soil salinity above 6%, are all factors that can endanger the health of the tree.

Insects

The red palm weevil (Rhynchophorus ferrugineus) is a deadly insect of Asian origin which spread to the Mediterranean in the 90s and currently strikes more than 5% of the palms on the Arabian peninsula. The infection is recognizable by the yellowing of the plant’s leaves and the characteristic odor of rot. Once the palm is attacked, it must be isolated and treated with integrative methods; the entire plantation must be put in quarantine and treated with chemical disinfectants.

White scale (Parlatoria blanchardii) is an enemy of the date palm cultivators at a global level. The insect sucks the lymph from the leaves and dates leaving discolored areas and ruining the production. Various insects (natural enemies) and sometimes mineral oils and chemical insecticides are used to control it.

Red scale (Phoenicococcus marlatti) is very diffuse, but difficult to detect, and does not cause serious damage to the plantations.

Bou Faroua (Oligonychus afrasiaticus), or Old World date mite, is diffuse in North Africa and the Middle East. It feeds on dates and reproduces within them, causing them to drop.

The caroub moth (Ectomyelois ceratoniae), also called “Ver de la Datte” in French, is a larvae that is diffuse in Asia and the Mediterranean, and particularly fond of dates. It strikes the dates in the plantation as well as those that are stored. It can be warded off by fumigations, protecting the fruit bunches and removing the fallen dates.

The rhinoceros beetle (Oryctes rhinoceros Linné) is a large insect that feeds on palm leaves and date stems. It can be controlled by placing special types of traps.

The desert locust (Schistocerca gregaria Forskal) is diffuse in North Africa and the Middle East, and causes severe damage to the plantations. When a swarm of locusts arrives in the palm grove, the insects devourthe leaves and fruit, leaving the trunk of the palm nude. After such an attack, it takes about three years before the plantation can return to produce.

The date stone beetle (Coccotrypes dactyliperda) is a species that reproduces inside the date pit, damaging the fruit.

Termites (Microcerotermes diversus) can attack the roots and the trunk of the palm by burrowing vertical canals to reach the lymph. These can be controlled by removing and burning the affected trees and spreading poison for termites.

Root-knot nematodes (Meloidogyne spp.) parasites found in the soil, are miniscule worms that are only visible through a microscope. They attack the roots of the palm, causing blister-like formations. They are largely diffuse in the vegetation that surrounds the palm groves and are impossible to eradicate, unless the plant is removed and the land is subsequently regenerated.

Rodents

The black rat (rattus rattus) and the common rat (mus musculus) feed exclusively on dates, in both plantations and stock houses. Their underground galleries can damage irrigation canals and the trees’ roots, causing them to fall. They can be eliminated with poison.