RELATIONSHIPS BETWEEN CLIMATIC VARIABLES AND ASCOCHYTA BLIGHT OF CHICKPEA IN PUNJAB, INDIA

In a study of the correlations between Ascochyta blight disease of chi ckpea and weather variables over a 15-year period, maximum temperature and afternoon relative humidity (RH) were identified as two important variables for disease prediction. These variables provided consistent ly significant correlations from the 9th to 14th standard meteorologic al week. The relationship between disease and maximum temperature was linear, and that between disease and RH was an exponential asymptote. A ratio of these two weather variables, referred to as the humid therm al ratio (HTR), was best fitted by a quadratic function. Predictions o f disease over a 12-year period showed that there was better agreement (less scatter) between the predicted and observed values with HTR tha n either maximum temperature or RH alone. The use of HTR as a basis fo r a predictive scheme to advise on fungicide applications is suggested . (C) 1997 Elsevier Science B.V.