Altered acetylcholinesterase as a resistance mechanism in the brown planthopper (Homoptera: Delphacidae), Nilaparvata lugens Stal

Highly resistant strains of the brown planthopper were obtained after 30 generations of laboratory selection by carbofuran or fenobucarb. Topical LD sub50 for fenobucarb increased 93-101-times and topical LD sub50 for carbofuran increased 51-68-times on selection by either carbofuran or fenobucarb, while the LD sub50 for diazinon increased only 6-7-times by the same selections. Sensitivity of AChE to carbofuran or fenobucarb was reduced remarkably in vitro in the resistant strains while sensitivity to diazoxon changed only slightly. Insensitive AChE was considered to be the major resistance mechanism of the carbamate-resistant strains of the brown planthopper.