Epidemiological Studies of Alternaria tenuissima Causing Leaf Spot and Flower Blight of Marigold

Marigold is one of the most popular traditional flower crop and commercially grown in the South Gujarat. In the present study, field experiment was conducted on epidemiological studies of leaf spot and flower blight incidence of marigold caused due to Alternaria tenuissima during Kharif 2020 and 2021 at Floriculture Research Farm, NAU, Navsari on variety Punjab Gainda-1 under natural conditions. The maximum per cent disease intensity of leaf spot and flower blight incidence were recorded when maximum temperature was in the range of 29.8°C to 32.3°C, minimum temperature in the range of 23.2°C to 24.3°C, rainfall in the range of 67 mm to 148 mm, evening relative humidity in the range of 81.2% to 85.1% and bright sunshine hours of 2.9 hrs/day to 4.5 hrs/day, as they were most favourable conditions for the rapid development of leaf spot and flower blight of marigold. Correlation matrix revealed that the per cent disease intensity and flower blight incidence had highly significant positive correlation with maximum temperature and bright sunshine hours. By working out the stepwise regression it was noticed that at least 90.5 per cent variation in per cent disease intensity of leaf spot was due to function of weather parameters viz., rainfall and minimum temperature and for flower blight incidence 74.3 per cent variation was due to bright sunshine hours.