The sweet potato whitefly, Bemisia tabaci Gennadius biotype B (Hemiptera: Aleyrodidae), causes high economic losses in vegetables, beans, soybeans, peanuts, cotton, and several ornamental plants. Repeated spray applications of synthetic pesticides has led B. tabaci to develop resistance to numerous conventional insecticides, besides polluting the environment. In this work, we investigated the bioactivity of the essential oil of Pelargonium graveolens L'Her (Geraniaceae) (PG-EO) and some related monoterpenes against the sweet potato whitefly Bemisia tabaci Gennadius biotype B (Homoptera: Aleyrodidae) in tomato. This oil significantly reduced the number of B. tabaci adults on tomato leaflets. The deterrence experiments showed similar results for PG-EO, geraniol, and citronellol; however, citronellol was more effective than PG-EO. In fumigation tests, the essential oil of P. graveolens caused 100% mortality of adults of B. tabaci biotype B at concentrations from 0.5 mu L L-1 in air. The vapor toxicity of geraniol, linalool, and citronellol, the main chemical constituents of the essential oil of P. graveolens (PG-EO), was similar to that of PG-EO. These results suggest that PG-EO and its related monoterpenes are potentially applicable to develop effective natural product-based pest-management compounds.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)