Incidence of seedling blight disease of Raphia palm (Raphia hookeri Mann and Wendl.), the disease agent and its phytotoxic effect in the seedlings and nutrient property of soil at the Nifor sub-station, Onuebum, Bayelsa State

Abstract

A study of the incidence of seedling blight disease among Raphia hookeri palm seedlings in the Nigerian Institute for Oil Palm Research, Raphia Substation, Onuebum, Bayelsa State, Nigeria was carried out to determine the causal agent of the disease, phytotoxic- effect of the causal agent on the seedlings and assess the nutrient status of the R. hookeri seedling blocks. The disease incidence was 5%. Advanced stage of seedling blight was characterized by the lamina of the leaflets becoming fragile and gradually falling off, leaving tattered leaflets. Overall soil fertility was adequate, although the soil was poorly drained. Pathogenicity test and molecular analysis revealed that Diaporthe sp. was responsible for the disease. Results also showed that Diaporthe sp. likely released toxic substances which damaged the photosynthetic layer of the leaf tissues. This is the first report of Diaporthe sp. causing seedling blight in R. hookeri. Symptoms of the disease were similar to those caused by Glomerella cingulata usually seen in the rainy season. A study of the incidence of G. cingulata and Diaporthe sp in the seedling blight of R. hookeri during both rainy and dry seasons is suggested. Improved soil fertility might contribute towards the successful management of seedling blight disease caused by Diaporthe sp.