Enhancing Insecticidal Efficacy and Remedying Dilatory Effect of Diatomaceous Earth Sayan® against Adults of the Rice Weevil, Sitophilus oryzae (L.), in Combination with Myrtle Essential Oil, Myrtus communis L

In this research, insecticidal efficacy of the diatomaceous earth Sayan® in combination with a plant pharmaceutical formulation MG® containing myrtle (Myrtus communis L.) essential oil was evaluated on adult Rice weevils Sitophilus oryzae. Five doses of 0.125, 0.25, 0.5, 1.0 and 1.5 g Sayan®/kg grain in combination with MG® at four concentrations of 0 and estimated LC10, LC20 and LC50 (equal to 1267.0, 1790.0 and 3451.0 µl/L air, respectively) were assessed. All experiments carried out at 26±2ºC, 65±5% R.H. and L:D 16:8. Adults’ mortality was recorded after 24, 48 and 72 hrs of exposure. To determine progeny production at F1 and F2 generations, dead and alive adults were removed from treatment containers after the 72 hrs counts and containers were left at the same conditions for 45 and 90 days more. After these periods, emerged adults were counted (as dead or alive). Using Sayan® alone did not result in notable mortality even after 72 hrs so that at the highest dose of 1.5 g/kg it was 16.66%. Different doses and concentrations applied in combination increased the mortality significantly even after 24 hrs so that after 48 and especially 72 hrs it was highly notable and increased from about 80% by using LC10-0.125 g/kg after 48 hrs up to 100% by using the LC50-1.5 g/kg. No offspring produced by using treatments containing MG® essential oil but Sayan® applied alone resulted to progeny production in F1 and F2 generations. Results of this study indicated that applying the diatomaceous earth Sayan® in combination with the myrtle essential oil significantly increased the insecticidal efficacy of Sayan® and remedied dilatory effect of it (decreased the exposure interval form about more than 14 days down to about 72 hrs). This could be considered in the case of stored-products pest control.