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ThesisItem Open Access Studies on the management of bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2004-08) Acharya, Sushant; Sinha, A.P.Bacterial blight of rice caused by Xanthomonas oryzae pv. oryzae is known to occur in all the rice growing states of India. The severity and significance of damages caused by infection have necessitated the development of strategies to manage the disease, so as to reduce crop loss and to a best, an epidemic. The present investigation was undertaken to evaluate fungicides, antibiotics, botanicals /natural products against Xanthomonas oryzae pv. oryzae in vitro and under field conditions and to screen out rice germplasm/varieties against Xanthomonas oryzae pv. oryzae. Among the four antibiotics screened in vitro, against Xanthomonas oryzae pv. oryzae, chloromycetin was found most effective which gave maximum inhibition zone at all the concentrations tested followed by streptocycline, Kasu B and Penicillin. Of the four fungicides evaluated, carbendazim was found best in inhibiting the bacterial growth. Copper oxychloride was next in order of effectivity against the test organism. Among commercial formulations of botanicals tested, neem gold at 2000 ppm concentration resulted in maximum inhibition zone (13.6 mm) followed by Neem Azal, Trichure, Spictaf and Wanis, which produced inhibition zones of 10.6, 7.6, 6.0 and 3.6 mm, respectively. Among the five plant extracts, neem leaf extract was found best against the test organism. Cold water extract of haldi and hing did not produce inhibition zone at all the concentrations tested. Of the three natural products tested at 100 per cent concentrations, cow urine produced maximum inhibition zone (7 mm) followed by cow dung extract (4 mm). Field experiments were conducted during kharif 2003, to find out the most effective chemicals/botanicals/natural products against the disease. Among the antibiotics/fungicides tested, streptocycline + copperoxychloride gave maximum disease control and increase in the grain yield. Neem leaf extract was found next in order of effectivity in reducing disease index and increasing grain yield. Foliar spray with Neem gold, Neem Azal, haldi, hing, cow urine, cow dung and buffalo urine significantly reduced disease index and enhanced grain yield. Of the 197 rice germplasm/ varieties screened during kharif 2003 by artificial inoculation, under field conditions, 57 showed resistant/moderately resistant type of reaction. The use of botanicals/natural products identified in the present investigation offers a cheaper and environmentally safer alternative to antibiotics/fungicides for foliar sprays against bacterial leaf blight of rice.