Abstract

After a brief review of the literature on diseases of Albizia falcataria, the results are reported of a survey of diseases of the species in nurseries and plantations in Kerala, and of research on their characteristics and control. The nursery diseases found were web blight caused by Rhizoctonia solani, and seedling wilt caused by Fusarium solani. Extensive investigations reported on the former disease (which was very common) include: symptoms; pathogenicity; host/parasite relations; influence of isolate type, inoculum concn. and seedling age on infection; the effect of soil moisture on fungal growth; and chemical control - 'Bavistin' [carbendazim] was the most effective of 13 fungicides tested. Three diseases of plantation trees were found: dieback caused by Botryodiplodia theobromae; shoot dieback caused by Phomopsis mendax; and a partial bacterial wilt caused by a Pseudomonas species resembling P. solanacearum. The B. theobromae dieback was the most common and serious disease of the three and investigations are reported on its incidence and severity, progress and spread, symptoms, identification of the pathogen, and its pathogenicity. The disease was less severe in plantations with no fire history, no cattle grazing and no tapioca [cassava, Manihot esculenta] cultivation (as a taungya crop); absence of these factors (or use of a different taungya crop) is therefore recommended as a control measure against this wound pathogen