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Bursaphelenchus cocophilus
Introduction
Bursaphelenchus cocophilus (Cobb) causes red ring disease of palms. This disease was first seen in coconuts in Cedros, Trinidad in 1905. It is now wide spread in the Caribbean and Latin America wherever coconuts are cultivated.

Identity
Authority Classification Kingdom Phylum Class Order Family Genus Species Synonyms : Cobb, (1919)

: Animalia :Nemata : Secernentea : Aphelenchida : Aphelenchoididae : Bursaphelenchus : cocophilus : Aphelenchus cocophilus Cobb, 1919; A. (Chitinoaphelenchus) cocophilus (Cobb, 1919) Mico- letzky, 1922; Aphelenchoides cocophilus (Cobb, 1919) T. Goodey, 1933; Chitinoaphelenchus cocophilus (Cobb, 1919) Chitwood in Corbett, 959;Rhadinaphelenchus cocophilus (Cobb, 1919) Goodey, 1960. Common name: Red ring nematode.Signs & Symptoms
Red Ring Disease A ring of discoloured tissue is the most characteristic symptom of red ring disease of coconut and other palms (Fig.1). Trees are normally susceptible to the disease for two years before and after they come into bearing. Older and younger trees generally exhibit a high degree of resistance. Infected trees show yellowing, usually of the lower leaves, startingat the tips of the pinnae and progressing towards the leaf base. Fig. 1: Vertical and horizontal cuts The yellowing is followed by browning and the through trunk of coconut to reveal the leaves eventually die. The yellowing and typical “red ring”, the primary symptom browning spread to other leaves and the tree dies of “ red ring” disease of palms caused by Bursaphelenchus cocophilus between sixand 16 weeks after the first Photo Credit: Dave G. Hutton appearance of symptoms. Shedding of green nuts of all sizes takes place with or slightly in advance of leaf discoloration and sometimes is the first symptom of disease. Shedding of open and unopened flowers and partial withering of branches of the inflorescences may also occur. Trees with infected roots show drooping leaves and droopingbunches of coconuts, the nuts often falling prematurely. The advanced stages of infection may be associated with putrefaction of the soft tissues of the stem and base of the central

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column of unexpanded leaves and sometimes the tree breaks off at the neck. Infested roots change colour from white to yellow, pink, dark yellow or red-brown, and their bark sloughs off. Although the classical redring symptom occurs in most infected stems, solid red pith has been observed in infected trees in El Salvador. A toxin produced by the breakdown of coconut tissue may be associated with the disease. A toxic principle caused wilting in tomato (Lycopersicon esculentum) and in three small palms (Ptychoraphis augusta, Licuala spinosa and Thrimax morissi) which were used as indicator plants. Wateruptake of infected coconut palms was markedly less than that of healthy trees and showed that the xylem vessels of infested trees are occluded. B. cocophilus also causes little-leaf disease of coconut and oil palm in Surinam and Guyana. The disease is characterized by leaves being reduced in size and standing stiffly upright; pinnae are short, wiry and necrotic terminally; yellowish suberized patchesappear on leaf bases and petioles and older leaves turn yellow to grey. The disease was produced experimentally in oil palm and in the wild palm, Mauritria flexuosa. It has been reported from some of the same areas as red ring.

Morphology
Female: Body about 1 mm long and very slender (a = 60-96), arcuate to nearly straight when relaxed; cuticle thin, marked with transverse straie 0.6-1 apart;lateral fields with four incisures and a faint median line, suggesting a fifth incisure, occupying 0.25 of body-width; deirids and phasmids absent. Lip region smooth, high, anteriorly flattened with rather straight sides, slightly narrower than body; head framework prominent, sclerotized. Spear 11-13 long, attenuated, knobbed at base but knobs may be obscure, especially on immature specimens;...