Effect of environmental factors on disease and spore population development of Colletotrichum lagenarium causing anthracnose of bottle-gourd in Haryana

The role of weather parameters on the development of anthracnose of bottle gourd revealed that there was gradual increase in the disease severity up to end of October, however, steep increase in disease intensity was recorded from 3^rd to 15^th October. The weather parameters observed favourable for the maximum disease development were temperature (maximum) 34°C, temperature minimum around 18°C, relative humidity (morning) > 80%, evening > 40% and Growth Degree Days (GDD) > 16. The regression analysis of disease data with weather variables revealed that all the factors resulted R² value 0.90. However, temperature (minimum) and relative humidity (evening) alone gave R² value 0.88. It showed that these two factors contributed maximum in the progression of the disease. The spores of Colletotrichum lagenarium were first trapped on 12th September and their concentration increased up to end of October. The maximum spore population/day was recorded on 6^th October. The weather variables favourable for the disease development as mentioned above were also favourable for the spore production. The stepwise regression analysis of the data revealed that all the weather parameters produce R² value 0.62. However, temperature (minimum) and relative humidity (evening) were most contributing factors and produced R² value 0.58 alone. The correlation coefficient analysis revealed that all these factors contributed positively in the spore population production. The minimum leaf wetness period of 6 hrs was required for initiation of the disease. However, leaf wetness of 24 hrs. was essential for maximum diseases development