Insecticidal Efficacy of Paya®, an Iranian Diatomaceous Earth Formulation, Against Adults of the Granary Weevil, Sitophilus granarius (L.) (Col.; Curculionidae) on Wheat, Barley, Rice and Maize

In this study, efficacy of Paya® (Iranian diatomaceous earth) in different doses and exposure intervals on different grains evaluated against adults of the granary weevil, Sitophilus granarius (Col.; Curculionidae). All experiments carried out at 26 ± 2ºC, 65 ± 5% R.H., and continuous darkness. Adults’ mortality counted after 1, 2, 7 and 14 days on wheat, barley, rice and maize kernels treated with five dose rates of 0.125, 0.25, 0.5, 1 and 1.5 g/kg-1. To assess progeny production, all dead and alive adults were removed and treated grains left at the same conditions for 45 more days. Then, the number of adults emerged on treated grains was counted. Insecticidal efficacy of Paya® was highly affected by the type of grain, dose rate, and exposure interval. Observed mortalities after 1 and 2 days on four grains were very low for all doses. After 7-day interval, highest mortalities on wheat, barley and rice (14.52, 11.61 and 6.69 percent, respectively) occurred by using the highest dose, but in the case of maize, mortalities caused by doses of 0.5, 1 and 1.5 g/kg-1 reached up to 35.27, 40.90 and 38.26 percent, respectively. Insecticidal efficacy of Paya® was only notable on maize after 14-day interval and by using high doses of 1 and 1.5 g/kg-1 and it reached up to 95.83 and 90.14 percent, respectively. Evaluation of progeny production showed that numbers of F1 adult progenies were higher on barley (14.75-25.75 adults) and wheat (4.75-21.75 adults), respectively. The lowest progeny productions were also observed on rice (0.0-0.25 adults) and maize (0.5-3.11 adults), respectively, which had no significant differences at all doses used. As a conclusion, 100% control of adults of this pest especially on barley and wheat is needed for suppression of population increase at F2 and following generations.