NITROGEN-FERTILIZER EFFECT ON SELECTION, ACCEPTANCE, AND SUITABILITY OF EUPHORBIA-PULCHERRIMA (EUPHORBIACEAE) AS A HOST-PLANT TO BEMISIA-TABACI (HOMOPTERA, ALEYRODIDAE)

Changes in nitrogen content of poinsettia, Euphorbia pulcherrima Willd enow (Euphorbiaceae), is an important factor influencing its acceptabi lity and suitability to the sweetpotato whitefly, Bemisia tabaci (biot ype B) (Gennadius). More whiteflies were found on fertilized plants th an on nonfertilized plants. Higher oviposition on ammonium nitrate tre ated plants than on nonfertilized or calcium nitrate treated plants su ggests that acceptability of a plant by the whitefly is in response to plant cues. These cues reflect changes in nitrogen content and are pe rceived during probing of the leaf surface by female whiteflies. Altho ugh more crawlers were produced from eggs laid on nonfertilized or cal cium nitrate treated plants than on ammonium nitrate-treated plants, m ore adults were produced from fertilized plants than from nonfertilize d plants. High mortality during the crawler and young nymphal stages o n nonfertilized plants could be caused by nutritional limitations of u nfertilized plants.