05 Jul Purple Blotch- A major threat for onion growers
प्याज उत्पादकों के लिए बड़ा खतरा जांभळा करपा या बैंगनी धब्बा रोग Onion is susceptible to numerous foliar, bulb and root pathogens that reduces the quality and yield. Among the pathogens Alternaria porri, which causes purple blotch disease of onion is a serious menace in onion producing countries of the world. Found in all places where onions and garlic grow. The disease is also known as leaf spot or blight disease of onion and is the most destructive disease during kharif and rabi and drastically reduces the yield by upto 97%. The intensity of the diseases varies from season to season, variety to variety, and region to region. Symptoms: In this disease, initially small, suppressed, oval spots on the leaves which turn mostly purple-brown in colour. These spots gradually increase and initially purple spots later turn black. The leaves fall due to the wound. The lesion starts from the upper part of the old leaves. Plants become soft and weak from the neck. The flower stems also twist and fall. This disease can cause 50 to 70 percent damage. Symptoms of Purple blotch Colony and conidial morphology of Alternaria Porri Disease cycle and favourable conditions: The disease is more prone to outbreak in Kharif season. Normally 18 to 20°C. Temperature and more than 80 percent humidity, frequent...