Spatial distribution pattern of rice leaf beetle (Oulema oryzae Kuwayama) and simple plan for deciding whether to control it
1999
Hachiya, K. (Hokkaido. Central Agricultural Experiment Station, Naganuma (Japan)) | Nakao, H. | Hashimoto, Y.
A farmer-oriented simple plan for determining the sampling field, sampling hills and sampling procedure of egg-mass and deciding whether to control rice leaf beetle was proposed, based on the spatial distribution pattern of egg-mass throughout fields and in a field. On opposite sides of a paddy field and among neighboring paddy fields where rice was cultivated by the same method, the difference of egg-mass population density was generally less than double. Therefore, it was considered that a sampling field and sampling plots should be chosen randomly from several fields for the sake of the farmers convenience. Plots near the field edges, however. should be excluded from sampling where population density tended to differ slightly from other parts of the field. It was proved that the frequency dispersal of egg-mass number of each hill obeyed a random distribution at middle and high population density fields, so a concrete method of examining egg-mass density was proposed based on sequential sampling theory, distribution pattern and economic injury threshold of the pest. The examination needed only five to ten hills per field, which seemed to be practical for farmers
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