Field Evaluation of Fungicides against Alternaria and Corynespora Leaf Spot Pathogens on Cotton

Author: Duddu Mahesh, S.L. Bhattiprolu, V. Prasanna Kumari and Ch. Chiranjeevi

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Abstract

In India, cotton crop is affected by foliar diseases estimated to cause yield losses ranging from 20 to 30 per cent. Among them Alternaria and Corynespora are the major leaf spot diseases. In view of the importance a field experiment was conducted to evaluate common fungicides for both leaf spots during kharif 2020-21. The experiment was laid out in randomized block design (RBD) with seven treatments viz., myclobutanil @ 0.1%, propiconazole 0.1%, hexaconazole @ 0.2%, metiram + pyraclostrobin @ 0.3%, copper oxychloride @ 0.3% and fluxapyroxad + pyraclostrobin @ 0.06%along with control and three replications. Severity of leaf spots was recorded by adopting 0-4scale at seven days interval before and after spraying and per cent disease index (PDI) was calculated. Propiconazole @ 0.1% was found effective against Corynespora leaf spot with lowest per cent disease index of 4.67 and 87.61 per cent decrease in disease whereas hexaconazole @ 0.2% reduced Alternaria leaf spot (6.08 per cent disease index) to an extent of 70.08 per cent. The highest cotton seed yield (2493kg ha-1), benefit cost ratio (1.68) and maximum incremental benefit cost ratio (15.25) were obtained with propiconazole @ 0.1% with 37.50 per cent increase in yield over unsprayed control. Next best was hexaconazole @ 0.2% with 2347 kg ha-1 seed cotton yield, 1.55 benefit cost ratio and 8.31 incremental benefit cost ratio.

Keywords

Alternaria, Corynespora, Cotton, fungicides, management

Conclusion

On the basis of these results it is concluded that three sprays of hexaconazole @ 0.2% and propiconazole @ 0.1% at 15 day interval gave highest disease control of 70.08 per cent and 69.67 per cent, respectively, against Alternaria leaf spot. In case of Corynespora leaf spot disease, three sprays of propiconazole @ 0.1% at 15 days interval resulted in the highest disease reduction of 87.61 per cent Propiconazole @ 0.1% recorded the highest seed cotton yield of 2493 kg ha-1 with B:C ratio of 1.68 and maximum ICBR (15.25) followed by hexaconazole @ 0.2% with seed cotton yield of 2347 kg ha-1, 1.55 BCR and 8.31 IBCR.

References

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How to cite this article

Duddu Mahesh, S.L. Bhattiprolu, V. Prasanna Kumari and Ch. Chiranjeevi (2022). Field Evaluation of Fungicides against Alternaria and Corynespora Leaf Spot Pathogens on Cotton. Biological Forum – An International Journal, 14(4): 292-297.