Vol. 10, Issue 6 (2021)

Author(s):
CH Yamuna, SL Bhattiprolu, V Prasanna Kumari and CH Chiranjeevi

Abstract:
The effect of weather factors on the development of fungal foliar diseases in LHDP-1 cotton variety was investigated during kharif 2018-2019. The data on per cent disease index (PDI) of Corynespora leaf spot, grey mildew and rust were recorded at three days interval under high density planting system (HDPS) and normal planting system (NPS) along with weather parameters. Correlation between progress of disease severity and weather factors was calculated and multiple regression equations with independent weather variables were derived using Excel programme to identify the critical parameters for development of diseases. Maximum temperature, morning relative humidity and evaporation accounted for 74 per cent (R²=0.74) variation in PDI of Corynespora leaf spot under HDPS whereas minimum temperature, morning relative humidity and rainfall contributed for 79 per cent variation under NPS. In case of grey mildew evaporation in combination with rainy days and wind speed caused 71.5 per cent variation in PDI while morning relative humidity coupled with minimum temperature accounts for 88.6 per cent variation in NPS. Morning and evening relative humidity along with minimum temperature accounted for 82.9 per cent variation in rust PDI under HDPS whereas morning relative humidity, sun shine hours and wind speed contributed for75.9 per cent variation under NPS. The differences in the significant parameters indicate the role of microclimate in both planting systems.