Rev 08/04/2023
Bursaphelenchus cocophilus (Cobb, 1919) Baujard, 1989
Red Ring Nematode
Synonym: Rhadinaphelenchus cocophilus
Rhadinaphelenchus was designated a junior synonym of Bursaphelenchus by Baujard (Revue Nematol 12:323-324, 1989) as it has all the same characters including a subterminal bursa; but differs only in having a greater length to width ratio ('a' ratio), being very long and slender.
Caudal papillae occur throughout the Aphelenchina.
Drawing from Cobb and Maggenti
Nematode is 1.0-1.2mm long.
Female: Genus is characterized by vulval flap.
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
West Indies, South and Central America.
No California pest rating.
Naturally infects coconut and oil palms, can be artificially inoculated into cabbage palm and a few others.
Ecophysiological Parameters:
Nematode has a 10 day life cycle, and can migrate and survive in soil, especially moist areas, but tree to tree spread seems minimal.
Nematodes can be transmitted by putting infected tissue in soil near healthy trees, but nematode survives free in soil only 3-4 days.
Insect vector is Palm (Coconut) Weevil, Rhynchophorus palmarum.
Nematodes are carried on body surface and also enter body through spiracles and mouth.
Transmission to leaf axils occurs as beetle feeds.
Trees may die 4 months after first symptoms appear.
Symptoms include band of discolored, reddish-brown tissue about 5 cm from edge of leaf stems; discoloration extends into leaf petioles. Red ring (3-4 cm wide) may appear up to 8'(2.4 m) above soil line. Nematodes are numerous in and around the discolored tissues; adults are usually located at inner edge of red ring.
Up to 5000 nematodes can be found per gram of tissue; greatest numbers occur 6-12" (15-30 cm) below upper limit of ring.
Roots are similarly discolored, with soft, spongy cortex.
There is apparently a phytotoxin in the red ring. Damage causes reduction in water uptake by tree.
Discoloration occurs before appearance of leaf symptoms (and can be detected by stem borings); allows roguing to prevent spread.
Bait traps for vector control: ground coconut shells and Sevin (Cocosev) in Trinidad or use of Lannate bait traps.
In Mexico, Palm Weevil control has reduced incidence of nematode infestation from 10% to 1%.
Recent developments with baited traps include use of a pheromone (Rhynkolure) to attract the palm weevil to banana treated with insecticide (Cid del Prado, pers. communication). The combination of removal of infested plants and the use of pheromone traps is very effective.
Resistance
Host Plant Resistance, Non-hosts and Crop Rotation alternatives:
Baujard, P. 1989. Remarques sur les genres des sous-familles Bursaphelenchinae Paramonov, 1964 et Rhadinaphelenchinae Paramonov, 1964 (Nematoda: Aphelenchoididae.Revue de Nematologie12:323-324