A Wilt of Coffea liberica in Surinam and its Association with a Flagellate, Phytomonas leptovasorum Stahel

SYNOPSIS. A description is given of a disease of Coffea liberica Bull ex Hiern. occurring in Surinam, British Guiana and, according to previous investigations by Stahel, also in Brazil, San Salvador, and Colombia. The symptoms and spreading of the disease are described and its relation to a fungus disease of coffee with very similar wilting symptoms. Special attention has been paid to the concurrence of the observed flagellate Phytomonas leptovasorum Stahel and the multiple division of the phloem vessels on account of the scepticism with which Stahel's discovery of the flagellates in sieve tubes of wilting coffee trees was met by other research workers. Moreover a short description is given of experiments to transmit the disease to healthy coffee trees by grafting, with special reference to the successful root grafting. Furthermore it could be ascertained that no viruses or nematodes are involved as pathogens. The possible relation between the disease and insects is still unsettled; observations of flagellates in the midgut of certain bugs, found on the roots of coffee trees, seem to indicate that the vector of the phloem necrosis disease is a Hemipteran insect. Although no final proof of the pathogenicity of the flagellate can be given, secondary indications support the theory that the flagellate Phytomonas leptovasorum is the cause of the phloem necrosis disease of Coffea liberica in Surinam.