Effects of some insecticides against tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae) and egg parasitoids Trichogramma brassicae and T. evanescens (Hym.: Trichogrammatidae).
Tomato leaf miner, Tuta absoluta (Meyrick) (Lep.: Gelechiidae), is one of the most important pests of tomato in the world. In the current study, effects of four insecticides, abamectin, emamectin benzoate, acetamiprid, and flubendiamide were tested against 1st larval instar and pupae of the tomato leaf miner. Also, their lethal effects were studied on the adult stage of two species of egg parasitoids, i.e., Trichogramma brassicae and T. evanescens. The leaf miner collected from greenhouses near Arak (Markazi province, Iran) were reared for three generations under laboratory conditions and then treated by the leaf-dip method at larval or pupal stages. The parasitoids were tested by coated vial residue method. Insect mortality was recorded 24 h after initial exposure. The LC50 values of abamectin, emamectin benzoate, acetamiprid, and flubendiamide were 0.92, 0.13, 1.51, and 0.34 µg/ml, respectively for the 1st larval instar and 4.99, 2.25, 3.22, and 3.48 µg/ml, respectively for the pupae. Similarly, the LC50 values of the above-mentioned compounds were 0.0013, 0.0029, 0.0058, and 1.53 µg/ml, respectively for T. brassicae and 0.0014, 0.0025, 0.0052, and 1.71 µg/ml, respectively for T. evanescens. The maximum number of parasitized eggs was seen on the 2nd day after the emergence of both parasitoids. These amounts for T. brassicae after treatment by LC25 of flubendiamide, acetamiprid, emamectin, and abamectin, were 14.70 ± 0.17, 14.00 ± 0.20, 13.1 ± 0.20, and 11.8 ± 0.14, respectively which statistically differed with the control (16.00 ± 0.12). For T. evanescens, the related values were 13.10 ± 0.21, 12.37 ± 0.12, 11.50 ± 0.18, and 11.23 ± 0.16, respectively which differed meaningfully from the control (14.00 ± 0.19). Risk quotient categorized flubendiamide in class 2 (slightly harmful) and other compounds in class 3 (harmful). Based on our results, flubendiamide showed selectivity and it can be used as an effective tool for integrated pest management programs of tomato leaf miner.