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
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.
Nematode has a 10 day life cycle, and can migrate and survive in
soil, especially moist areas, but tree to tree spread seems
Nematodes can be transmitted by putting infected tissue in
soil near healthy trees, but nematode survives free in soil only
Insect vector is Palm (Coconut) Weevil, Rhynchophorus
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
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
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.
Host Plant Resistance, Non-hosts
Baujard, P. 1989. Remarques sur les genres des sous-familles Bursaphelenchinae
Paramonov, 1964 et Rhadinaphelenchinae Paramonov, 1964 (Nematoda:
Aphelenchoididae.Revue de Nematologie12:323-324