Residual toxicity of some insecticides on Tuta absoluta (Lepidoptera: Gelechiidae) larvae under laboratory conditions

Tomato leaf miner (TLM), Tuta absoluta (Meyrick), is a destructive insect pest in greenhouses and fields on tomato plants. In this study, the efficacy of seven insecticides: spinosad (Laser®), chlorantraniliprole (Coragen®), indoxacarb (Steward®), abamectin (Vertimec®), metaflumizone (Alverde®), azadirachtin (NeemAzal®), and Bacillus thuringiensis was evaluated against T. absoluta during 30 days from spraying. Tomato plants were sprayed by half and a quarter of the recommended field concentrations of the insecticides. Thirty 2nd instar larvae were placed on the treated plants, 2, 4, 7, 10, 13, 17, 22, 26, and 30 days after treatment, and mortality was recorded 48 hours later. The results showed that spinosad and chlorantraniliprole in the half of the field recommended concentration caused maximum efficacy on T. absoluta larvae, 100 and 80 % mortality at the end of 30 days, respectively. On the other hand, indoxacarb caused 57 % mortality on the 22nd day after exposure to the quarter of the field recommended concentration. In the quarter field-recommended concentration, abamectin and metaflumizone also had moderate mortality (52 and 54 % on the 10th day). The application of these three compounds can be considered suitable for preventing an increasing pest population from reaching the economic injury level. Bacillus thuringiensis var. kurstaki and azadirachtin insecticides had slight mortality and short persistence on this pest. Experts and farmers can select the appropriate compounds to control this pest based on the pest population status according to the obtained results.