Effect of selected fungicides on Brown spot disease of rice caused by Helminthosporium oryzae
Abstract
The in-vitro test of selected fungicides against brown spot disease incidence of rice and development of a disease prediction model base on weather variable was conducted during two Kharif seasons from 2014-2015 to 2015-2016. Results revealed that among the selected fungicides treatment lowest percent disease incidence was found in Propiconazole in both the cropping season (2014-15) and (2015-16) with minimum mean percent disease index (PDI) value bcd (7.76) and (7.03) with percent disease control of 72.39 and 73.09 respectively over the control, followed by Propineb (PDI) value bcd (8.6) and (7.23) with percent disease control of (69.40) and 73.09 respectively of the two cropping seasons. Among the fungicides treatment highest disease incidence was found in Thiophanate with maximum mean percent disease index (PDI) value bcd (17.03) and (14.98) with percent disease that control of 39.41 and 42.67 respectively in both the cropping seasons. It was also found disease intensity was higher during the first cropping season (2014-15) as indicated by higher mean percent disease index (PDI) value abcd (12.5**) whereas in the following cropping season (2015-16) with lower value of (PDI) value abcd (11.18**).
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Introduction
Proper evaluation of fungicides available in the market is required to identify the efficacy of a particular chemical against the target pest which will avoid economic losses as most chemicals are costly. Its indiscriminate use has serious effect on natural environment and is a global issue that needs to address through judicious application system. Brown spot disease of rice caused by Heminthosporium oryzae (Breda de Haan) is a major fungal disease which has been reported to occur in all rice growing countries including Japan, China, Burma, Sri Lanka, Bangladesh, Iran, Africa, South America, Russia, North America, Philipines, Saudi Arabia, Australia, Malaysia and Thailand (Ou, 1985; Khalili, et al. 2012). In India the disease was known to occur in all rice growing states but more severe in dry and direct seeded rice in the state of Bihar, Chhatisgarh, Madhya Pradesh, Orissa, Assam, Jharkhand and West Bengal (Gangopadhyay, 1983; Ou, 1985; Sunder, et al., 2014). This particular disease has been reported to cause enormous losses ingrain yield upto 90% particularly when leaf spotting phase assumes epiphytotic proportions as observed in great Bengal famine in 1942 (Ghose et al. 1960) and in general can cause yield loss upto 45% when no protection was given.
Conclusion
Chemical indiscriminate use need to be addressed through proper screening and evaluation and its judicious application practices need to be advocated at the highest level by the end users or the farming community. In our present investigation among the selected fungicides, Propiconazole and Propineb at 1000ppm applied at 48 days after the paddy transplantation and consecutive two sprays at 10 intervals was found most effective against brown spot disease of rice and its severity.
