Fungal diseases of sesamum in Kerala

Abstract

Only limited information is currently available on the fungal diseases of sesamum in Kerala. During the course of the present study 12 fungal diseases could be identified and among these, leaf spots caused by Botryodiplodia theobromae and Pestalotia sp. are new records. Investigations were carried out to find out the losses caused by the major fungal pathogens, viz., Alternaria sesami, Colletotrichum gloeosporioides, Curvularia lunata, Botryodiplodia and Fusarium oxysporum f. sp. sesami. Loss estimation studies conducted revealed that all the above fungi reduced the yield considerably. Rhizopus nigricans, Aspergillus flavus, A. niger and Mucor haemali were the common fungi found associated with sesamum seeds. Mode of entry, histopathology and toxin studies were conducted with the five major fungal pathogens. These varied with different organisms. Survival ability of the five species of fungi ranged from three months in A. sesami to elevan months in B. theobromae and F. oxysporum f. sp. sesami. In vitro evaluation of fungicides, in general, revealed that, Bavistin, Bordeaus mixture and Dithane M-45 were superior to the other fungicides tested, and in the field experiment Bavistin was found to be the best. The residue levels of carbendazim of Bavistin sprayed sesamum leaves and pods were below the maximum residue level fixed. Application of fungicides caused alterations in the acid value, iodine value and saponification value of sesamum oil. Bavistin was found to be the most efficient as well as economical fungicide in controlling the leaf spot diseases of sesamum. Varietal screening trials showed Si. 866, Kayamkulam-2, Si.44, Trivandrum local and North Kerala local No.24 as resistant/tolerant varieties against the five species of fungi.