A laboratory assessment of the lethal and sub-lethal effects of four insecticides considered for commercial control of the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae).
The tomato leaf miner, Tuta absoluta (Meyrick), is a key pest of the Solanaceae, which is commercially controlled worldwide using insecticides. In this study, the toxicity of various concentrations of four insecticides, a thiamethoxam + lambda-cyhalothrin combination, indoxacarb, acetamiprid, and hexaflumuron, were assessed against second-instar larvae of T. absoluta. Results showed that indoxacarb with a LC50 value of 7.13 mg a.i./l was more toxic than acetamiprid, thiamethoxam + lambdacyhalothrin, and hexaflumuron. Sub-lethal effects of insecticides on demographic and biological parameters of T. absoluta were evaluated using LC30 concentrations estimated from bioassays. The lowest intrinsic rate of increase (rm) was shown in indoxacarb treatments (0.083/day). Except for hexaflumuron, the net reproductive rate (R0) and gross reproductive rate (GRR) were significantly lower in all treatments compared to the control. The shortest and longest adult longevities were shown in the indoxacarb treatment (18.92 days) and the control (26.94 days), respectively. The lowest fecundity was observed in the indoxacarb treatment (46.62 offspring/female). Except for hexaflumuron, the pupal weight was significantly decreased in all insecticide treatments. With the results of this study, combined with acute toxicity data, the significant adverse effects of indoxacarb, acetamiprid, and thiamethoxam + lambda-cyhalothrin on demographic and biological parameters of T. absoluta larvae were determined providing support for their consideration in commercial use in suppressing this pest.