Pathogenicity of Steinernema carpocapsae and Heterorhabditis bacteriophora on tomato leafminer, Tuta absoluta

Tomato leafminer moth (Tuta absoluta) is a serious pest of tomato crops which could impose upto 100% yield loss. This study was designed to assess the pathogenicity of third stage juveniles (IJs) of Steinernema carpocapsae (Sc) and Heterorhabditis bacteriophora (Hb) on different instars of pest larvae in Petri dish and in a leaf bioassay. The most virulent nematode was selected for the following tests. The ability of different concentrations of the more efficient species in parasitizing the last instar larvae (L4) and pupae in Petri dish (50, 100 and 200 IJs/Petri dish) and pupae in soil (50, 100 and 200 IJs/cm2 soil) was determined. In greenhouse, the efficacy of the selected species against different larval stages of pest was examined and compared with chemical pesticide, indoxacarb. Hb was selected as the better species since its controlling ability was approximately 1.7 times more than Sc. 50 IJs of Hb per Petri dish parasitized 84% of pest’ L4. The highest mortality of pupae in Petri dishes (40%) and soil (28%) was achieved when IJs were respectively applied at a rate of 200 IJs/Petri dish and 200 IJs/cm2 soil. Increase in IJs’ concentrations resulted in higher mortality of pupae. In greenhouse, the most susceptible stage of pest to Hb was L4, while the chemical pesticide had a little effect on pest's larvae. According to the results, it seems that Hb could alleviate the damage and produce acceptable control level of the pest.