Also called “Le Coeur qui penche” in French, the bending head is a minor disease observed in Algeria, Egypt, Mauritania and Tunisia (Munier, 1955). The central cluster of fronds takes the form of an erect fascicle with a bent tip. The trunk bends and may even break.
Thielaviopsis paradoxa and Botryodiplodia theobromae Pat are fungi commonly isolated from declining palms (Brun and Laville, 1965). Effi cient maintenance and appropriate sanitation of the date plantation is the first control measure. Diseased parts of infested palms are to be collected and burnt in order to limit the spread of the disease.
Originally this disease was first reported by Fawcett and Klotz (1932) in USA. Other cases were found in Algeria, Egypt and Tunisia (Djerbi, 1983). According to Djerbi, the disease is characterised by whitish, irregular blotches and streaks on the leaf stalks, midribs and pinnae that become outlined by reddish brown margins.
The name “dry bone” comes from the drying out of the surface of the leaf stalk with a hard, smooth and white appearance. Lesions, from one to several centimetres, involve only the epidermis and a thin layer of subjacent tissue. According to Fawcett and Klotz (1932), a bacterium is commonly found associated with the lesions, and certain palms are more susceptible than others.
Laville and Sachs (1967) reported this disease of unknown cause from Mauritania. Affected palms, present a parasol form produced by the old and mid-level fronds, while new fronds present a short rachis with an irregular arrangement of pinnae and spines. Leaves remain green during the first stages and then decline and become yellow. The terminal bud assumes a conical form and becomes a stunted rosette.
All these symptoms are accompanied by the abortion of the axillary buds, resulting in failure of fl owering for one or two seasons before foliage symptoms appear. Two to four years is the average duration of the disease from the appearance of the symptoms to the death of the palm. According to Djerbi (1983) no varietal resistance has been observed.
Also called “Rapid decline”, rhizosis is a minor but fatal disease of unknown cause. The first symptom is premature falling off of fruits. However, if the attack is sometime after fruit development, the fruit withers and shrivels on the bunch. A reddish-brown discolouration of pinnae appears on mature fronds and the disease progresses from the bottom to the top of the fronds which rapidly die.
Offshoots die with the diseased mother palm and the disease is hence self-limiting. According to Djerbi (1983), no varietal resistance has been observed.