Sheath Blight (ShB) (C.O. Rhizoctonia solani Kühn) is one of the most devastating diseases of rice particularly in wet season. The disease has spread in all rice growing areas in large scale and in some areas it is due to widespread cultivation of susceptible variety, as in case of West Bengal and Odisha where ‘Swarna’ (MTU 7029) which is widely cultivated and is highly susceptible to sheath blight pathogen ‘R. solani’. Damage is estimated upto 100% in favourable climatic condition and yield loss of rice varies from 5.2-50% depending on disease severity. Though cultivation of resistant variety is the best option to cope up the attack of this pathogen but till date no such variety is available to the growers. Thus, in present situation cultural practices combined with foliar spray of fungicide is the most common practice to manage the disease and even in integrated pest management system need based application of fungicide has been recommended.
In this context, a long term experiment was conducted to evaluate the efficacy of new generation bio-rational fungicide of ‘strobilurin derivatives’. Strobilurins (also known as β-methoxyacrylates) or QoI (Quinone outside Inhibitors) fungicides, launched in 1996 are analogues of strobilurin-A originally derived from natural products (Strobilurus tenacellus, a wild mushroom growing in forests). Strobilurins, are now the second largest chemistry group of fungicides, widely used on cereals and, more recently, on soybeans (a market that reached $600 million in 2004). The strobilurin fungicides mainly act on mitochondrial synthesis in cytochrome bc1, are highly effective, and are suitable for a wide range of crops include Azoxystrobin, Fluoxastrobin, Kresoxim-methyl, Metominostrobin, Picoxystrobin, Pyraclostrobin and Trifloxystrobin