Chrysanthemum leaf blight caused by Alternaria alternata (Fr.)Keissler

Among the several diseases, Alternaria leaf blight is one of the most destructive foliar disease which causes heavy loss in chrysanthemum. Survey during kharif/rabi 2007 revealed that Alternaria leaf blight was severe in all four districts of survey. Isolation and morphological studies revealed Alternaria alternata (Fr.) Keissler as causal organism. The per cent disease index (PDI) was found positively correlated with maximum temperature and rainfall, while minimum temperatures, relative humidity (morning and evening) were negatively correlated with PDI. In vitro evaluation revealed that, Propiconazole, Hexaconazole, Iprodione and Chlorthalonil were found effective. Out of six plant extracts Nimbicidin was found effective. Among bio agents, Trichoderma harzianum was most effective against Alternaria alternata. In field evaluation of fungicides, botanicals and bioagents Hexaconozole (0.1%) was found effective in reducing the PDI. It gave higher quality and yield of flowers and also found economical to the farmers.