• The Korean Journal of Pesticide Science
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• v.9 no.4
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• pp.365-373
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• 2005

This study was carried out for looking into the status of susceptibility of pest insects to insecticides. Each insect Brown planthopper(BPH), Green leaf hopper(GLH), Smaller brown plant hopper(SBPH), Rice water weevil(RWW), were captured at various areas where the host crops were being cultivated and the susceptibility level of each pest insect was investigated. The susceptibility of each pest insect varied by insect species and areas where they were caught. BPHs kept higher level of susceptibility comparing to susceptible reference strain except to most of tested insecticides except imidacloprid (Resistance ratio was 68). The susceptibilities of GLH and SBPH to most of insecticides for their control did not developed markedly since 1976 except fipronil and imidacloprid which is widely used for WRR control. The insecticides used for control of WRR were very effective even at the concentration of one fourth of recommending concentration, but in 2000 suwon strain of WRR showed markedly reduction of susceptibility to carbofuran.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.19
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• pp.1-6
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• 1975

From the cross Tongil$^2//IR833/IR1317$ glutinouse rice lines wx 126 were bred. Some of these lines were earlier than standard variety and later than glutinous check variety. Some of them yielded as much as standard variety and showed better resostances to blast, stripe deseases and smaller brown plant hopper than standard variety. It was sosscussed that, theough the vreedong procedure, following points were proved, 1)back-cross program in roce breeding was effocoent, 2)semi-dwarf plant type of "Tongil" has high yielding poteneoality and 3) the variety "Tongil" was a good for recurrent parent for back-cross program. back-cross program.

• Korean Journal of Soil Science and Fertilizer
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• v.4 no.1
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• pp.1-11
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• 1971

1. Rice plant grown with silica had more elect leaves and heading was one week earlier with silica than without silica grown in both water culture and Akiochi soil. 2. Silica content of rice plant was apparently increased by silica application and the increase insilica was more increased by bassal application of silica than top dressing. The content of other eements in plant decreased with silica application and the trend was most noticeable in iron. 3. Rice plant low in silica were more susceptible to reaf blast, Helminthosporium, mites and smaller brown plant hopper. 4. There was no significant effect of silica on increasing the dry matter production of rice plant grown on water culture, but silica remarkerbly increased the dry matter production of rice plant grown on Akiochi soil. The increasing effect of silica on rice grown on Akiochi fields was more noticeable than that of grown on Pots. 5. In rice plant grown on Akiochi soil, number of spikelets and percentage of ripened grains were increased by application of silica. The silica effects can be increased by application of well balanced nitrogen and potassium ratio. 6. From these results, it can be concluded that silica seems to have no direct effect on rice growth, but application of silica to Akiochi soil associated with low silica supply may be critical for healthy growth of rice plant, and silica directly related to rice agronomy.