Toxicities of Carbofuran showed different patterns by three application methods, Drench(as systemic effect), Leaf dipping(as contact and systemic effects) and Topical(as contact effect) applications. LC50 dropping pattern was L-shape in Drench, low slope line in Topical and intermediate of them in Leaf dipping. Drench application was the most Carbofuran treatment method to Brown planthoppers. Dropping patterns of LC50 were almost same between resistant and susceptible strains. The checking time of Carbofuran toxicity was suggested to be 2nd day after application by SD analysis of mortality. Resistance ratios were peak on 3rd day after application in Drench, 4th day(Susceptible) and 5th day(Resistant) in Leaf dipping and showed steady increase line pattern in Topical application.

• Siwoo Lee(Crop Cultivation and Environment Research Div. National Institute of Crop Science)
• Jin-Kyo Jung(Crop Cultivation and Environment Research Div. National Institute of Crop Science)
• Bo-Yoon Seo(Crop Protection Div. National Academy of Agricultural Science)
• Chang-Gyu Park(Korea National College of Agriculture and Fisheries)