A New Method of Applying Imidacloprid to Potted Plants for Controlling Aphids and Whiteflies

Abstract

The effectiveness of two application methods of the insecticide imidacloprid in controlling 1) melon aphids (Aphis gossypii Glover) on `Nob Hill' chrysanthemum (Dendranthema ×grandiflora Ramat) plants and 2) silverleaf whitefly (Bemisia argentifolii Bellows & Perring) on `Freedom Red' poinsettia (Euphorbia pulcherrima Wild.) were compared. Plants were grown in containers with their interior covered by a mixture of flat latex paint plus several concentrations of imidacloprid (0, 10, 21, 42, and 88 mg·L−1), or treated with a granular application of the insecticide (1% a.i.) according to label recommendations. All imidacloprid treatments effectively reduced aphid survival for at least 8 weeks. The two most effective treatments were the granular application (10 mg a.i.) and the 88-mg·L−1 treatment (0.26 mg a.i). All imidacloprid treatments effectively reduced whitefly nymph survival. The 42- and 88-mg·L−1 treatment and the granular application (1% a.i.) were equally effective in reducing nymph numbers in lower poinsettia leaves. None of the plants given treatments with paint exhibited any phytotoxicity symptoms. These results suggest the possibility of a new application method for systemic chemicals with the potential of reducing the release of chemicals to the environment. Paint and imidacloprid mixes are not described in any product label and cannot be legally used by growers. Chemical name used: 1-[(6-chloro-3-pyrimidil)-N-nitro-2-imidazolidinimine (imidacloprid)