Biotype Q of Sweetpotato whitefly, Bemisia tabaci (Homoptera: Aleyrodidae) was raised in seven tomatoes and eight red pepper varieties; however, biotype B did not grow in red pepper varieties. Rokkusanmaru variety of tomato and Cheongpungdaegun variety of red pepper showed the highest susceptibility to biotype B and Q. HPLC (ELSD Detector) analysis showed that the presence of sugars such as erythritol, xylose, xylitol, fructose, glucose, mannitol, and sucrose in red pepper varieties; erythritol, xylose, fructose, glucose, and mannitol was in tomato varieties. Tomato varieties lacks xylitol and sucrose, which were present in the red pepper varieties. Subsequent bioassay with these two sugars, sucrose did not show significant difference between two biotypes; however, xylitol was showed only repellent effect against B biotype. Therefore, it seems that xylitol may play a key role in the selection of host plant by biotype B of sweetpotato whitefly.