Alternaria blight of linseed (Linum usitatissimum L.) and its chemical management: A comprehensive review

Alternaria blight is an important disease of Linseed (Linum usitatissimum L) that hampers its productivity and oil content. Symptoms first appears on lower leaves as black point that gradually increased in size to become circular to oval or irregular in shape. During severe infections, spots coalesce and cover the large area of the leaves. The pathogen also attack on the other foliar part of the plant. Alternaria linicola Groves & Skolko and Alternaia lini Dey are two fungi known to cause Alternaria leaf blight in linseed. Studies of relative dominance of pathogens associated with the diseased tissue revealed the dominance of Alternria linicola in infected tissue in comparison to A.lini. Evaluation of genotypes against Alternaria leaf blight under artificial epiphytotic condition revealed that resistance and tolerance is present in the linseed germplasm. Various number of plant protection chemicals were tested during the past years and Rovral @ 0.2% and mancozeb @ 0.2% was found most effective in many experiments. propiconazole @ 0.1% and hexaconazole @ 0.1% were found effective to combat against the Alternaria blight. Iprodione, Propiconazole, Hexaconazole, Difenconazole, Carbendazim 0.10%, Capton 0.20%, Carbendazim 12% + Mancozeb 63% and iprobenphos have been noted to manage the disease economically. Early sowing was also found effective for reduction of Alternaria. Aqueous leaf extracts of Azadirachta indica and Lawsonia inermis was also found suppressive to disease. Spray of Salicylic acid and Benzoic acid was reported to reduce the disease by enhancing the immunization in the linseed plant.