Sumatra disease in cloves induced by a xylem‐limited bacterium following mechanical inoculation

Suspensions of a Gram negative, non motile nutritionally fastidious bacterium, cultured from clove trees affected by Sumatra disease and inoculated by needle puncture into the xylem of seedling cloves and young trees, caused the death of over 60% of the plants withing 2 year. Bacteria, confined to zylem vesssels, occurred throughout the vascular systems of dying plants and were also still active in some of the plants which survived for 3 years after inoculation. Bactria resembling those used as inoculum were readily reisolated form dying plants but not from any water‐treated controls. Symptoms in experimental plants and the appearance and distribution of vessels occluded by bacteria were indistinguishable from those resulting from natural infection. All clove types tested were susceptible, including progeny from trees which had survived past disease attack. Result suggest the importance of using vigorously growing plants and providing protection against full sunlight during incubation for the successful establishment of beacterial infection in juvenile clove plants follwing mechanical inoculation.