| Summary: | 碩士 === 國立中興大學 === 昆蟲學系所 === 96 === There are three species of rice stem borers in Taiwan: Chilo suppressalis (Walker), Scirpophaga incertulas (Walker) and Sesamia inferens (Walker), which feed on rice and cause ‘dead heart’ during vegetative phase and ‘white head’ during reproductive phase of rice. In Japonica rice production regions of southern counties, Sesamia inferens was an overwhelming majority and Chilo suppressalis was a minority, but Scirpophaga incertulas was not discovered. In the north counties (Miaoli, Hsinchu, Taoyuan and Taipei), Chilo suppressalis was a majority and Sesamia inferens was a minority. Besides these two stem borers, Scirpophaga incertulas was also discovered in north of Miaoli County. However in the Indica rice production regions, such as Changhua and Chiayi, Chilo suppressalis increased significantly and Sesamia inferens became a minority. Chilo suppressalis collected from different counties were tested for their susceptibility to carbofuran, chlorpyrifos, cartap, permethrin and fipronil. The results showed that the Chilo suppressalis collected from southern and central counties (such as Chiayi, Changhua and Taichung) were less susceptible to five tested insecticides than those of northern counties (Miaoli, Hsinchu and Taoyuan). Chilo suppressalis of Chiayi and Changhua strains had very high resistance to carbofuran, while did not show significant resistance to chlorpyrifos, an acetylcholinesterase (AChE) inhibitor like carbofuran. Therefore, carbofuran and chlorpyrifos-oxon were used to study the association of AChE insensitivity and carbofuran resistance in Chiayi and Changhua Chilo suppressalis. The result showed that carbofuran was a less potent inhibitor to AChE of these Chilo suppressalis. Compared to the AChE of Hsinchu strains, the AChE of Changhua strain had higher activity under inhibition of carbofuran and chlorpyrifos-oxon, but the AChE of Chiayi strain had same activity with Hsinchu strain. The synergistic effect of piperonyl butoxide (PBO), s,s,s-tributyl phosphorotrithioate (DEF) and diethyl maleate (DEM) to carbofuran has decreased resistance of Chiayi Chilo suppressalis up to 105-fold. These results implied that the resistance of Changhua Chilo suppressalis was due to the insensitive AChE and the resistance of Chiayi Chilo suppressalis was due to increase of detoxification.
|
|---|
