• Korean journal of applied entomology
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• v.29 no.4
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• pp.257-268
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• 1990

The regional characteristics in the occurrence of the rice stem borer, Chilo suppressalis (Walker), in Korea, were examined by analyzing the light trap data obtained from 39 locations during the years of 1965-1988, and some ecological significance of the overwintering larval populations collected from the four locations where some of the typical ecological-race have been known, the results obtained are as follows; The total number of the moths have decreased greatly throughout the nation since 1970. The decrease in the total number of moths related with those in the spring moth but not in the summer moths, and suggested that the changes in the rice production systems have effected significantly on the second generation of the insect. The variations between the regions had been gret in 1960's, decreasing phase in 1970's and increasing phase in loast decade. The overall average of 50% emergence dates have shifted earlier in both moths, and the changes were different considerably with the regions as wheel as in generations. When the overwintered larvae were incubated at $25^{\circ}C$ and RH of 90%, the average mortalities were 21.07% for Suweon, 43.06% for Iri, 63.51% for Jinju, 27.04% for Gwangju. When the overwintered larvae were incubated at $25^{\circ}C$ and RH of 90%, the average mortalities were different with the body weight; 45.44% for the larvae of less than 39 mg, 37.61% for 40-49 mg, 37.28% for 50-59 mg, 30.17% for greater than 60 mg. When the overwintered larvae wee incubated at $25^{\circ}C$, post-diapause larval development periods of body weight classes were 18.6$\pm$1.2 days for the larvae of less than 39 mg, 20.4$\pm$3.3 days for 40-49 mg, 21.4$\pm$3.2 days for 50-59 mg, 21.8$\pm$3.2 days for grater than 60 mg, and only the larvae of less than 39 mg, body weight class less than 39 mg was found statistically different in post-diapause larval development periods. From these results, the changes in the cultural practice of the rice have effected on the ecological pattern of the rice stem borer, and the effects seemed to be different with the generations, and with the regions where the different ecological races are distributing.