Stemphylium Blight of Onion: A Review

Onion (Allium cepa) is one of the most important crop grown throughout the world. Onion suffers from many diseases caused by fungi, bacteria, viruses, nematodes and abiotic factors. Among them fungal diseases stemphylium blight is the most serious and devastating disease of onion limiting the quality and quantity of both bulb and seed. The present review is mainly focused on variability associated with Stemphylium vesicarium and its integrated management. Variability studies are important to document the changes occurring in the population and individuals with variability in morphological, cultural and pathogenic characteristics so as to breed the varieties with durable resistance to the stemphylium blight of onion andidentification of source of resistance against the range of virulence present in the pathogen population. Further, management of stemphylium blight of onion through fungicide application is feasible, however, long term usage of fungicides has led to the resistance development in pathogens besides hazardous environmental consequences associated with their use. The most efficient and economical method to mitigate the menace of this disease is therefore, integrated disease management (IDM) approach where other non-chemical ecofriendly management strategies are integrated with chemical methods in order to manage the diseases more efficiently with reduced use of chemicals. Among non-chemical ecofriendly management strategies biological control is gaining interest as an alternative or complement to chemical treatment of the disease. The present review paper deals with distribution, symptomatology, pathogenicity, variability and integrated management.