Sweetpotato whitefly, Bemisia tabaci (Gennadius), is an important pest of many crops, with an extremely wide host range. Management strategies using natural products, e.g., plant extracts, might be alternatives for control of this pest. Ethanolic extracts of Chenopodium ambrosioides L., Piper nigrum L., Thymus vulgaris L., and Origanum vulgare L., were evaluated. C. ambrosioides ethanolic extract at 6% concentration killed 93%; P. nigrum at 4 and 5% concentrations killed 96 and 98%, respectively; T. vulgaris at 11% concentration killed 94%; and O. vulgare at 12 and 15% concentrations killed 98 and 100% of whiteflies. P. nigrum was most toxic with a lethal concentration 50 (LC₅₀) of 1.6%. All extracts were positive for tannins and flavonoids. P. nigrum was very positive for alkaloids, tannins, and saponins. These spices are inexpensive and easy to cultivate in Mexico and are available as raw material for production of extracts with insecticidal activity. They are harmless to humans and are much used in the culinary arts.