Studies on Leaf Spot Disease of Croton: Codiaeum Variegatum L. Blume

Six locations were surveyed for the incidence and severity of leaf spot disease of croton. Four different fungi; Rhizopus sp., Aspergillus niger, Fusarium sp. and Botryodiplodia theobromae were isolated from the diseased leaves. Fusarium sp. and B. theobromae were found to be causal pathogens of the leaf spot disease. Three Trichoderma species namely; T. viride, T. harzianum and T. longibrachianum were tested as potential antagonists of the causal organisms and were found to inhibit the growth of the pathogens when paired in-vitro. The pairing was done simultaneously, antagonist before pathogen and pathogen before antagonist. Statistical analysis of the result showed that the effect of the three antagonists is significant as well as the effect of the treatment(timing of inoculation). The effect of the pathogens on the antagonists is insignificant. The mode of antagonism was found to be by competition for space, antibiosis and mycoparasitism.