Effects of emamectin benzoate combined with acetamiprid, eforia and hexaflumuron against Tuta absoluta (Lep.: Gelechiidae)

Abstract

Tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) is one of the most destructive pests of tomato in many parts of the world including Iran. The toxicity of emamectin benzoate alone and combined with acetamiprid, eforia (thiamethoxam + lambda-cyhalotrin) and hexaflumuron was evaluated against 2nd instar larvae of Tuta absoluta (Meyrick) under 25 ± 1 °C, the relative humidity of 75 ± 5% and a photoperiod of 16:8 (L:D). Also the mixtures of tested insecticides with emamectin benzoate at LC15:LC15 ratio were evaluated on the activity of general esterase enzyme and total protein content of 2nd instar larvae. After 96 hour, emamectin benzoate had the highest toxicity (LC50 = 0.52 mg A.I./L), followed by acetamiprid (LC50 = 56.39 mg A.I./L) and eforia (LC50 = 312.01 mg A.I./L). Hexaflumuron showed no toxicity against larvae. The combination of emamectin benzoate with acetamiprid at LC50:LC50 ratio produced synergistic effects and all of the other ratios showed additive effects. The emamectin benzoate combined with either eforia or hexaflumuron at all of the ratios produced additive and antagonistic effects, respectively. Esterase activity of larvae increased when emamectin benzoate was mixed with either acetamiprid or eforia, but no significant differences were seen between emamectin benzoate alone and its mixture with hexaflumuron. The combination of emamectin benzoate with tested insecticides significantly reduced the total protein content of larvae. According to the results of this study, the mixtures of acetamiprid and eforia with emamectin benzoate showed higher negative impacts against 2nd instar larvae than emamectin benzoate alone