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 pulcherri ma Willdenow ex Klotsch, can be controlled with imidacloprid applied by sub inigation. Different amounts of imidacloprid uptake by the growing medium w ere obtained by not watering the subirrigated plants for 0, 1, 2, or 4 d be fore the imidacloprid application. These treatments resulted in absorption of 12-175 mi of imidacloprid solution by the growing medium. These treatmen ts were compared with untreated control plants and plants that were treated with a standard drench application (100 mi) to the top of the growing medi um. All imidacloprid treatments resulted in a significant decrease in both the survival of adult whiteflies and number of immature whiteflies on the p lants. Subirrigation treatments resulted in better control of adult and imm ature whiteflies than drench application. Withholding water for 2 or 8 d be fore the imidacloprid application by subirrigation improved control of imma ture whiteflies. This indicates that the application of imidacloprid to poi nsettia by subirrigation is a practical and efficient method to control sil verleaf whiteflies.