Control of bacterial wilt of tomato by soil treatments
1997
Patcharin Khongplean
Virulent strain of Ralstonia solanacearum (Pseudomonas solanacearum), T10, causing bacterial wilt of tomato was isolated from tomato field soils in Chiang Rai province. This T10 strain was identified as biovar 3. Bacillus subtilis strains CH4 and CH6 and Pseudomonas fluorescens strain NA1 were tested for antagonistic activity against R. solanacearum T10 by paper disc diffusion method. B. subtilis strain CH6 was found to be the most effective antagonist. For biological control of bacterial wilt in greenhouse, application of antagonist powder was more effective than its suspension. Application of the antagonist twice was more effective method comparing with one application, population of R. solanacearum was lowest when treated with the antagonist twice. In the greenhouse, soil amendment with a standard rate of 68.5 kg/rai urea and 800 kg/rai lime (urea:lime = 1:1) 40 percent wilt whereas nonamendment led to 100 percent wilt. Application of urea:lime at 1:4 rate was the most effective comparing with 1:2 4:1 1:1 and 2:1 in which they were 32 38 40 58 and 65 percent wilt disease, respectively. For study on source of calcium, there was no different on disease control and R. solanacearum population when used either as lime, marl or dolomite for soil amendment. In field experiment, the soil amendment, solarization, chemical and antagonist treatments were effective for the disease control than nontreatment in which disease incidences were 19 47 19 44 and 67 percent, respectively. Population of R. solanacearum decreased at first application and there were no detection in soil amendment and chemical treatments at 56 days after application. Results on this experiment indicated that soil amendment with urea and lime was effective for control bacterial wilt whereas source of calcium was not different for disease control but increasing amount of lime was more effective than increasing amount of urea.
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