A wilt disease of coconuts from Trinidad associated with Phytomonas sp., a sieve tube‐restricted protozoan flagellate

Abstract

SUMMARYA wilt disease of coconut palms in Trinidad has been responsible for the death of more than 15 000 palms in the last 2 years. Symptoms of the disease include: loss of nuts, premature browning of successively younger leaves, necrosis of open and unopened inflorescences and of the young unexpanded leaves at the centre of the crown; rotting of the growing point, stem apex and roots.Samples from each of 10 diseased palms contained flagellates which were classified as trypanosomatid protozoans of the genus Phytomonas. The protozoans, which by squeezing could be expressed easily from tissues for observation by phase contrast light microscopy, were 1–1.5 μm wide and 27 μm long including the flagellum which was approximately 7 μm long.Sections of inflorescence rachillae from diseased palms revealed that the phytomonads were restricted to the sieve tubes. Phytomonas was always associated with diseased palms but it was never found in healthy palms.A brief description of the ultrastructure of the presumed pathogen of wilt disease is also given.