Acute and chronic toxicity of Ziziphora clinopodioides and Ferula gummosa essential oils against Plodia interpunctella (Lepidoptera: Pyralidae)

Growing concerns of chemical pesticides lead the researchers around the world to find new avenues of insect pest control. Plant essential oils could be considered as one of the ecofriendly alternative for synthetic pesticides. In the present research, lethal and sublethal toxicity of Ziziphora clinopodioides Lam. and Ferula gummosa L. oils were studied against Plodia interpunctella (Hübner). Results of bioassays showed that the estimated LC50 values of Z. clinopodioides and F. gummosa oils were 96.98 and 49.82 µl/l air against one-day-old eggs and 40.68 and 38.91 µl/l air for four-day-old eggs, respectively. LC50 values of Z. clinopodioides and F. gummosa oils were 10.12 and 7.49 µl/l air on 1st instar larvae and 34.11 and 12.66 µl/l air on 5th instar larvae, respectively. Moreover, Z. clinopodioides oil (LC50 = 25.77 µl/l air) was significantly more toxic than F. gummosa oil (LC50 = 28.72 µl/l air) to the adult moths. Based on the estimated LT50 values, it was determined that persistency of Z. clinopodioides and F. gummosa oils were 6.31 and 7.56 days, respectively. Increasing the oils concentration resulted in a significant increase in oviposition deterrenc. Also, hematology assays indicated that total hemocyte population of one-day-old 5th instar larvae was decreased as the oils concentration and exposure time increased. Collectively, results of the present study demonstrated the potent fumigant toxicity of Z. clinopodioides and F. gummosa oils against P. interpunctella. Also, tests on different growth and developmental stages of the studied moth showed clearly differential susceptibility levels of this pest against the oils.