Discovery of Scripus juncoides Roxb. var. Ohwianus T. Koyama resistant to sulfonylurea herbicides, and development of a control method based on its ecological characteristics
2006
Kohara, H.(Hokkaido. Central Agricultural Experiment Station, Naganuma (Japan))
Scripus juncoides Roxb. var. ohwianus. T. Koyama (S. juncoides), a perennial sedge, was one of the most serious paddy weeds since 1960 until the advent of modern herbicides in the 1980's. S. juncoides was easily controlled by sulfonylurea (SU) in the 1990's in Japan. Since around 1995, however, this sedge has been observed in various parts of Hokkaido, Japan in spite of the usage of SU This study was conducted first to determine the possible reasons for the survival of S. juncoides after SU treatment, then to find how herbicide-resistant S. juncoides appeared and finally to establish a new method for their control. The first chapter of this thesis is a review of the history of SU usage in Hokkaido, and studies on the biological characters of herbicide-resistant weeds and their control. In chapters 2 - 6, results of the studies on the response of S. juncoides to SU are described. For establishment of the control method, I surveyed the geographical distribution and level of infestation of S. juncoides, and examined the effects of several kinds of herbicides having different sites of action on the SU-resistant S. juncoides. In addition, to determine the effective time and duration of herbicide application, I examined the germinability and surviving period of S. juncoides seed.
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