Epidemiology And Control of Brown Leaf Spot (Drechlera Oryzae) of Paddy Under Upland Condition

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Date
1994
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Birsa Agricultural University, Ranchi
Abstract
(0.055 per cent day-1) and severity (0.036 per cent day-¹) were recorded during September month. The disease incidence and severity were (+)vely correlated with temperature (0.885 and respectively), 0.8374, relative humidity (0.7888 and 0.7889, respectively), and rainfall (0.7996 and 0.8313, respectively) but, (-)vely with sunshine hours (-0.3287 and -0.6968, respectively). The optimum levels of N, P and K with respect to disease suppression and maximum grain yield, were observed to be 100, 60 and 40 kg h -1 respectively. Disease incidence and severity showed highly significant (+)ve correlation, but, both of them showed (-) ve correlation with grain yield. The loss in grain yield ranging from 45.51 per cent to per cent were observed while assessing three rice 56.20 cultivars for their loss in grain yield due to brown leaf spot disease under upland field conditions. Of the 71 different cultivars screened against D. oryzae under both natural and artificially inoculated conditions, 7 varietiesviz IR-12-9-4, Mutant-7, Ratna x RAU 40.45-3-17, BR 8 Mutant, BR 8 Mutant (Ma) Kr and IR 18348-36-3-3 and OR 164-5 (IED 7252) were found to be resistant, 44 moderately resistant and 20 moderately susceptible. Five sprays of crude extract (10 per cent) of Impatiens balsamina or Solanum nigrum at an interval of 15 days gave satisfactory control of the disease. In biological control, three sprays of Bacillus megaterium at a concentration of 10000 cells m1-1, 48 hours ahead of pathogen's inoculation and at an interval of 20 days could control the disease under upland conditions. The best control was achieved with three sprays of Kitazin (0.1 per cent) followed by that of Salvistin (Carbendazim). Maximum economic turn-over of Rs 4.12 from an investment of Rs 1.00 was obtained from spraying Kitazin (0.1 per cent) thrice during fungicidal control of the brown leaf spot disease of rice.
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