Imidacloprid applications by subirrigation for control of silverleaf whitefly (Homoptera: Aleyrodidae) on poinsettia.

The objective of this study was to determine whether silverleaf whiteflies, Bemisia argentifolii Bellows & Perring, on poinsettia, Euphorbia pulcherrima Willdenow ex Klotsch, can be controlled with imidacloprid applied by subirrigation. Different amounts of imidacloprid uptake by the growing medium were obtained by not watering the subirrigated plants for 0, 1, 2, or 4 d before the imidacloprid application. These treatments resulted in absorption of 12-175 ml of imidacloprid solution by the growing medium. These treatments were compared with untreated control plants and plants that were treated with a standard drench application (100 ml) to the top of the growing medium. All imidacloprid treatments resulted in a significant decrease in both the survival of adult whiteflies and number of immature whiteflies on the plants. Subirrigation treatments resulted in better control of adult and immature whiteflies than drench application. Withholding water for 2 or 4 d before the imidacloprid application by subirrigation improved control of immature whiteflies. This indicates that the application of imidacloprid to poinsettia by subirrigation is a practical and efficient method to control silverleaf whiteflies.