Effect of temperature and ph on growth of Alternaria tagetica, leaf blight of marigold

Marigold (Tagets erecta) is one of the most important major floriculture crop in India. The leaf blight of marigold is caused by Alternaria tagetica is becoming a common disease on marigold Alternaria blight appeared in mild to severe form in many regions of Maharashtra and sometimes resulting in complete failure of the crop especially during rainy season. The fungal pathogen are greatly influenced by environmental factor therefore the present work undertaken to study the effect of temperature and pH on growth of Alternaria tagetica. The effect of temperature and pH were determined by colony diameter method by using different media like potato dextrose agar and oat meal agar medium. It is clearly evident from the result that all the temperature pH tested showed variation in the diameter of colony. The temperature 25°C encouraged better growth of Alternaria tagetica as compared to 15°C and 35°C. The result also revealed that pH 6 and 7 encouraged better growth of Alternaria tagetica it is concluded from the result that temperature 25°C and pH 6 is optimum temperature and pH for the growth Alternaria tagetica.