Residues of imidacloprid insecticide and its efficacy on whitefly, Bemisia tabaci (gennadius) in tomato plants

Abstract

The present work was conducted to evaluate the efficacy of imidacloprid against the whitefly, Bemisia tabaci infesting tomato plants under field conditions and its residues in leaves and fruits after different periods of application, using root treated seedling, treated seeds and foliar spray techniques. The root treated seedling was more effective than treated seeds in decreasing different stages of whitefly population. The reduction percentages of egg, nymph and adult stages in root treated seedlings and sprayed with half and field rates were more than that in untreated seedlings. The fruit yield was increased in root treated tomato seedlings sprayed with the recommended rate of imidacloprid compared to root untreated seedlings. Residues of imidacloprid in leaves and fruits in root treated seedlings sprayed with field rate were more than root untreated seedlings and sprayed, as well as the residues of imidacloprid were higher in leaves than fruits. The residual level of imidacloprid in fruits was less than maximum residual level (MRL = 1 mg kg−1) which recommended by Codex Alimentarius Commission. Half-life (t 1/2) was 7.27 and 6.37 day for leaves and fruits of root treated seedling and was 7.14 and 4.88 day for untreated seedling and sprayed. Imidacloprid was more more toxic to white fly Bemisia tabaci and also, its residues were under maximum resuidual limits ( MRL) in tomato fruits after one hr (initial residues) of spraying and after different periods of treatment with field recommended rate, it is safe for consumers and effective against white fly, so it could be suggested to use in white fly integrated management.