Control measures of sheath blight on aromatic rice caused by Rhizoctonia solani Kuhn
1993
Siriwat Thuwangkawat
Rice sheath blight, causing by Rhizoctonia solani. The objective of this research was, therefore, aimed at finding control measures using biological and chemical control methods. Antagonistic effects of some microorganisms against R. solani were evaluated by both in vivo and in vitro methods. Two isolates of Trichoderma spp., T1 and T2, and one isolate of Chaetomium sp. (Ch) were obtained from paddy soil. Two strains of Bacillus spp. were obtained from water (Bw) and sclerotium of R. Solani (Bs). The results of in vitro experiment indicated that T1 and T2 showed high inhibitory effects on both vegetative growth and sclerotium production of R. solani. Chaetomium sp. and Bacillus spp. The average numbers of sclerotium in petridish with R. solani and each of the antagonists were 0, 7.25, 27.50, 28.00 and 30.50 for T1, T2, Ch, Bs, and Bw, respectively, as compared to 30.80 sclerotium in control plates. In vivo experiments were conducted in the greenhouse by using seed treatment and spraying techniques on Khaodokmali 105 and Basmati rice. Spraying of antagonists suspension to leaves and shoot of rice plants produced no significant effect on disease symptom and sevevity. Seed treatment, resulted in higher number of healthy seedling. Several fungicides were also evaluated for their effectiveness against R. solani under laboratory conditions using poison media technique. Carboxin and Terrachlor showed higherst toxicity to R. Solani with EC 50 of less than 0.1 mg/1 whereas carbendazim, benomyl, mancozeb, and validamycin were less toxic with EC 50 of 0.275, 5.84, 53.70 and more than 1,000 mg/1, respectively. Chemical were tested in the greenhouse on rice plants, carboxin and benomyl showed high efficacy in controlling rice sheath blight
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