Study on the effect of Bacillus thuringiensis on control of Ennomus quercinaria (Hafngel)

In order to control Ennomus quercinaria, toxicity of different concentrations of Bacillus thuringiensis on was studied against the larvae of this pest to estimate LC50 levels of this biopesticide in this study. Laboratory evaluations by dipping method indicated more sensitivity of second instar larvae than the first ones, so that LC50 values of 2.14 and 0.6 ppm were calculated for the first and second instar larvae, respectively. Then, three calculated concentrations (1, 2, 3 ppm) of B. thuringiensis were sprayed on 2-year-old Parrotia seedlings using a back mounted sprayer, followed by releasing 30 second instar larvae on the seedlings. Results of LSD test showed significant differences in the mortality of second instar larvae between the control (water) and each of the three B. thuringiensis concentrations (p<0.01). The highest mortality rate (62%) caused by a concentration of 2 ppm. In the field conditions, B. thuringiensis caused 35% mortality versus a mortality rate of 2.8% in the control. The results of this study can be an important step in introducing a low-risk and healthy compound for pest control in the forest ecosystem and its beneficial insects.