PREDICTION OF RED ROT COLLETOTRICHUM FALCATUM WENT INCIDENCE IN SUGARCANE UNDER FIELD CONDITIONS USING CLIMATIC VARIABLES ANIL KUMAR 1 SATYAVIR 1 and RAM NIWAS 1 1 Department of Plant Pathology, CCS Haryana Agricultural University, Hisar,125 004 -India 1 Background and objective Red rot caused by Colletotrichum falcatum Went is the most dreaded disease of sugarcane and occurs in most sugarcane growing countries of the world. Red rot become destructive during rainy season, indicating vital role played by environmental factors, Therefore, the present study was undertaken to develop quantitative relationship between climatic factors and red rot development in sugarcane- Materials and Methods Studies were conducted on susceptible cultivar Co 7717, planted during second fortnight of February in blocks of 7x3 meters with three replications. Canes (160-1901 plot) were inoculated by nodal method with freshly sporulating isolate CF02. There were six series of inoculations at an interval of 10 days starting from 5th July during 1994-95 and 1995-96. Observations and disease incidence (leaf sheath infection and systemic development of the disease in the canes) were recorded at weekly interval upto 12 weeks of inoculations. The data were analysed by taking 'Y' as dependent variable and climatic variable as independent variables using stepwise multiple regression analysis on MSTAT software. The best fit models of pooled data for both the seasons tested for all the inoculation periods. Results and Conclusions Red rot incidence on leaf sheath during July, 25 (R 2 =0.77) and August, 25 (R 2 = 0. 96) inoculation periods were better explained by weather parameters. The best fit model [Y=0.216-0.137RD+0.013RN] incorporates number of rainy days and rainfall for leaf sheath infection. Systemic development of red rot was also directly contributed by rainfall and number of rainy days. The multiple regression model accounts upto 86 per cent variation and have proved that rainfall, number of rainy days, evening relative humidity and minimum temperature are critical factors for systemic progress of red rot. These results confirms that of other studies on Colletotrichum spp. and pasture legumes [1] where temperature, humidity, rainfall and wetness duration have been most significant weather variables which influence infection. The role of air temperature plays significant role in red rot development [2]. During testing of models predicted red rot incidence followed the actual values in the field. Based on these regression models red rot risk can be estimated in the sugarcane field by using climatic variables and presence of pathogen inoculum on the cane leaf sheath. References <1b> 1. Chakraborty S, Billard L, 1995. Plant Pathology 44, 63-72- 2. Beniwal M S, Satyavir, 1991. Indian Phytopathology 44, 333-338