Evaluation of newer fungicides against diseases of rice especially rice blast

Abstract

The experiments for the evalution of newer fungicides against rice diseases were conducted at the Rice Research Station and Instructional Farm at Mannuthy during the first and second crop season of 1979-80. The objectives of this study were to find out the efficiency of the new foliar fungicide Panolil, against four rice diseases viz., blast, brownspot, sheath blight and stackburn and to evaluate the efficacy of the newer fungicides Panolil, Panoctine and Panoram as seed treatment fungicides. In the bioassay studies in vitro cent per cent inhibition of Pyricularia oryzae was obtained in 1000 ppm of Panolil, 2000 ppm of Panoctine, 500 ppm of Panoram, 250 ppm of Hinosan and Kitazin and 100 ppm of Agallol in potato dextrose agar medium. In all the fungicide incorporated liquid medium no growth was observed. Panolil (500 ppm), Panoctine (500 ppm), Panoram (1000 ppm), Hinosan (1000 ppm), Kitazin (1000 ppm) and Agallol (100 ppm) completely inhibited the growth of Drechslera oryzae in solid medium. In liquid medium also no growth was observed even in lowest concentration of Panoli, Panoctine and Agallol, 250 ppm and above concentration of Panoram and Kitazin. But growth was observed in all the lower concentrations of Hinosan. Cent per cent inhibition of corticium sasakii was not noticed even in 2000 ppm concentration of Panolil and Panoctine. Panoram and Kitazin at 250 ppm concentration and Hinosan at 500 ppm gave 100 per cent inhibition of C. sasakii. In liquid medium no growth of the fungus was obtained in any of the fungicidal treatments except in the lowest concentration of Kitazin. Panolil, Hinosan and Kitazin gave 100 per cent inhibition of Alternaria padwixkii only at 2000 ppm. Panoram at 1000 ppm and Agallol at 100 ppm gave 100 percent inhibition. In liquid medium growth was observed only in the lowest concentration of Panoram and Kitazin and in all the concentrations of Hinosan. The incidence of blast was low in both the seasons and in both the varieties. Two higher concentrations of panolil (1.5 kg/ha and 1 kg /ha) were equally effective as organophosphorus fungicides in reducing leaf infection, while against neck blast, Hinosan and Kitazin were better than Panolil. Brown spot disease was low in both the varieties during first crop and while in second crop season disease was notices only in Jaya. Panolil 1.5 kg/ha was found to be superior to Hinosan and Kitazin in reducing the disease. Sheath blight infection was low and was noticed only during the first crop in the variety Triveni. Panolil was as effective as organophosphorus fungicides in controlling the disease. Stackburn disease appeared on both the varieties in both the seasons. This disease was best controlled by higher concentrations of Panolil. Seed treatment and storage studies were conducted using the seeds collected from the first crop season. Newer fungicides panolil, Panoctine and Panoram and Agallol were used as seed treatment fungicides. The effect of delayed drying and storage, on seed microflora and deterioration of viability were also studied by using the seeds treated with different fungicides. An increased number of fungal flora was observed in untreated seeds compared to the treated ones. Generally the number of seeds associated with fungal flora increased on storage. For both rice varieties Agallol was found to be the best in reducing association of fungal flora on seeds while when the storage period was extended upto 32 weeks the highest concentration of newer chemicals were found to be on par with Agallol. When the seeds were stored for 16 weeks, the influence of delayed drying on germination was pronounced only when the drying was delayed beyond 6 days then the germination fell below 80 per cent. After 24 weeks of storage, the germination fell below 80 per cent even when the drying was delayed for three days. Agallol was found to be the best seed dresser, followed by the higher concentrations of newer fungicides. When the storage was prolonged for 32 weeks, satisfactory germination was obtained only for the seeds dried immediately and pretreated with Agallol and Panoram 1 g/kg and 1.5 g/kg.