Steer, Joan D.; Coates-Beckford, Phyllis L.
Author Affiliation, Ana.
Department of Life Sciences
A comparison of the pathogenicity of microorganisms associated with premature nutfall and budrot diseases of coconuts and black pod of cocoa
JAGRIST: The bulletin of the Jamaican Society for Agricultural Sciences
Date of Publication
Laboratory experiments were conducted to evaluate the effects of 17 isolates of various fungi and one bacterium associated with premature nutfall and budroot diseases of coconut and also Phytophthora palmivora from cocoa with black pod disease on the detached button nuts of various coconut cultivars. The pathogenic effects of different isolates of P. palmivora and Phytophthora katsurae on tetached pods of the cocoa cultivars >ICS 1', >ICS 95' and >ICS 98' were determined also. Lesions developed after button nuts of the red colour form of the 'Malayan Dwarf' cultivar were wound-inoculated with all the best organisms but their radii varied greatly, ranging from 1 to 30 mm after incubation for four days at 25°C. Thielaviopsis paradoxa, P. palmivora and P. katsurae produced lesions considerably larger than those caused by the other organisms. P. palmivora frequently produced larger lesions than P. katsurae. Unwounded, inoculated button nuts were not parasitized by any of test organisms. P. katsurae and P. palmivora from disease tissue of a coconut crown, a fruit and a cocoa pod were pathogenic to the button nuts of all the colour forms tested of the coconut cultivars 'Indian Dwarf', 'Malayan Dwarf', Maypan' and 'Panama Tall'. These fungal isolates, except that of P. palmivora from the coconut crown, were pathogenic to 'Jamaica Tal' also. For all cocoa cultivar tested, pods developed lesions of a significant size only when wound-inoculated with the coconut fruit isolate of P. palmivora and wound- or surface-inoculated with the cocoa pod isolate. It appears that, in Jamaica, premature nutfall disease can result from field infection of coconut fruit mainly by T. paradoxa, P. palmivora and P. katsurae, fungi known to cause budrot diseases here. However, field studies are needed to confirm this hypothesis. Many of the other associated fungi probably are involved in these coconut diseases as well. Also, in fields intercropped with cocoa and cocnuts, probably the black pod pathogen can serve as inoculum for cocnut diseases and some coconut strains of P. palmivora may be pathogenic to cocoa.....