Changes in nitrogen content of poinsettia,Euphorbia pulcherrimaWilldenow (Euphorbiaceae), is an important factor influencing its acceptability and suitability to the sweetpotato whitefly,Bemisia tabaci(biotype B) (Gennadius). More whiteflies were found on fertilized plants than on nonfertilized plants. Higher oviposition on ammonium nitrate treated plants than on nonfertilized or calcium nitrate treated plants suggests that acceptability of a plant by the whitefly is in response to plant cues. These cues reflect changes in nitrogen content and are perceived during probing of the leaf surface by female whiteflies. Although more crawlers were produced from eggs laid on nonfertilized or calcium nitrate treated plants than on ammonium nitrate-treated plants, more adults were produced from fertilized plants than from nonfertilized plants. High mortality during the crawler and young nymphal stages on nonfertilized plants could be caused by nutritional limitations of unfertilized plants.