Toxicity of piperine amide analogs toward the tomato pinworm Tuta absoluta (Lepidoptera: Gelechiidae) and risk assessment for two predators.
Nineteen amides (three of them unpublished) were synthesized and tested on Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), an important pest of Solanaceae plants worldwide. Three of these compounds (14, 15 and 16) presented high acute toxicity toward the pest, with LD50s of 3.68 (CI95 = 2.83-4.47), 6.46 (CI95 = 5.85-7.20), and 13.52 μg/mg (CI95 = 11.06-15.95), respectively. Amide 14 presented the fastest action (LT50 = 1.2 minutes, CI95 = 1.03-1.37), followed by amide 16 (LT50 = 18 minutes, CI95 = 9.96-26.04), and amide 15 (LT50 = 3.7 hours, CI95 = 0.69-6.71). When applied at a sublethal dose, they did not affect weight gain and leaf consumption of the pest. Bioassays were also conducted using the ant Solenopsis saevissima (Hymenoptera: Formicidae) and wasp Polybia ignobilis (Hymenoptera: Vespidae) to assess the toxicity of the amides against T. absoluta predators. Amides 14, 15, and 16 were harmless to S. saevissima but presented high toxicity toward P. ignobilis. Amides 14, 15 and 16 are potential hit compounds for the development of insecticides for T. absoluta control. However, their use should be carried out following the principles of ecological selectivity to mitigate potential adverse effects on non-target organisms.