The influence and reliability of weather parameters on incidence of downy mildew in grapes

A Statistical model was developed to study the influence and reliability of weather parameters on incidence of downy mildew in Grapes and subsequently to predict their incidence. The preceding week's weather variables were found to collectively predict mildew incidence, to the extent of 93.7 to 96.2 per cent. The coefficient of determination (R²) and mean squared error were used to evaluate the empirical model. Only three variables viz., Maximum temperature, Evaporation, and Relative humidity at 7.30 hrs could explain the variability in downy mildew incidence to the extent of 89.4 and 93.7%in backward pruning. Relative humidity minimum temperature and evaporation could explain the variability in Downy mildew incidence to the extent of 88% as against 96.2% in fore pruning. The model will be useful in determining the role of climatic factors in disease appearance and progression for devising suitable management strategy.