A series of experiments at 25 (+/-1) degrees C were conducted in which different application rates of diatomaceous earth (DE) formulation Protect-It at two levels of relative humidity, 40 and 55%, and at three exposure periods were evaluated for control of Rhyzopertha dominica (F). Test insects were placed in vials containing 40 g of soft winter wheat mixed with 0.25, 0.50, 1.00, 1.50 and 2.00 g DE kg(-1). At all rates except 0.25 g kg(-1), mortality was significantly different from that in the control at the relevant exposure period. After each exposure interval, dead and live insects were counted and removed, and the vial containing wheat was then returned to the appropriate humidity chamber for 8 weeks until F(1) adults emerged. F(1) progeny production was significantly different from the control group at all rates. Mortalities for 1, 2 and 3 weeks exposure were found to be 47 (+/-5)%. Despite the fact that mortality increased with increasing rate, total mortality was not achieved even at the highest rate of DE. F(1) progeny production decreased with increasing rate for both RH conditions, and containment of population for both RH conditions was achieved at 1.00 g DE kg(-1). For each exposure period, F(1) progeny production of R dominica decreased with increasing rate of DE, and population suppression was achieved at 1.00 g DE kg(-1) for all exposure intervals. In summary, Protect-It resulted in reduced F(1) adult progeny and containment of population was achieved at 1.00 g DE kg(-1) at which rate mortality was 77%.

A series of experiments were conducted in which label rate (0.3 g per kg of wheat) with diatomaceous earth (DE) formulation Protect-It. Exposure studies were carried out at two levels of relative humiditiy (40% and 55%), two levels of insect density (10 or 20 adults per vial), and three levels of exposure periods. Test insects were placed in vials containing 40 g of soft white winter wheat mixed with either 0 or 0.3 g ProtectIt per kg of wheat. After relating exposure periods for both insect density and relative humidity levels, highest mortality was only 16%. Mortality, regardless of the dose rate applied (0 and 0.3 g) were not significantly increased as the exposure period increased. Regardless of relative humidity (r.h.) (40% and 55%r.h.), mortality in control were not significantly increased as the exposure period increased for the same insect density. However, significant differences among the three exposure periods in 10 adults' density in 0.3 g DE application.Mortality was significantly increased in 10 adults' density. In this case mortality of R. dominica adults increased with the increasing of the exposure intervals. As for 20 adults' density, mortality in 0.3 g DE application was not significantly changed along with the exposure intervals. After insects were exposed for 1, 2, or 3 week, dead and live insects were removed, and the wheat in the vial were returned to relating humidity box and kept for 8 week until F 1 adults emerged. Then, the number of F 1 adult was counted. The mean numbers of F 1 adults on untreated wheat at all density and r.h. combinations, regardless of exposure periods were significantly higher than that of 0.3 g DE-treated wheat (Fig. 3). At each density and treatment, the mean number of F 1 adults at 55% r.h. were higher that that of 40%r.h. The comparison between adult densities at each r.h. and treatment showed that adult densities influenced the F 1 production of R. dominica and F 1 adults were always higher at 20 adults' density. The mean number of F 1 adults at each density, regardless of treatment progressively increased as the exposure period increased. Fewer progeny were produced at 10 adults' density compared to 20 adults' density for same exposure periods. The highest reproduction occurred in 3 week of exposure period for both insect densities. Regardless of adult densities, the mean number of F 1 adults was significantly increased as the exposure period increased (Fig. 5) for both control and 0.3 g DE treatment. Reduction of F 1 adults at 0.3 g DE application compared to control were found to be 76.88, 74.78 and 67.63% for 1, 2 and 3 week of exposure period, respectively.

Laboratory experiments were conducted to assess the insecticidal effect of the diatomaceous earth (DE) formulation Insecto ® against adult stage of Rhyzopertha dominica (F.) at two levels of relative humidity i.e. 40 and 55%, and three exposure periods of 7, 14, and 21 days. Test insects were placed in vials containing 40 g of soft winter wheat mixed with 0.25, 0.50, 1.00, 1.50 and 2.00 g kg -1 DE. After respective exposure periods, mortality in all dose rates except 0.25 and 0.50 g kg -1 was found to be significantly different from mortality in control. After each exposure interval, dead and live insects were counted and removed, and then the vial containing wheat was returned to corresponding humidity chamber for 8 weeks until F 1 adults emerged. For F 1 production, applications at all dose rates were significantly different from control group. Mortality regardless of dosage for 7, 14 and 21 days exposure intervals were between 27.67-33.40 %. Despite the fact that mortality increased with the increasing dose rate, total mortality was not obtained even at the highest rate of DE. F 1 production decreased with the increasing dose rates for both r.h. conditions. Containment of population was achieved at 1.50 g kg -1 of DE for 7 days of exposure period and at 2.00 g kg -1 of DE for 14 and 21 days of exposure periods. For each exposure intervals, F 1 production of R. dominica decreased with the increasing dose rates of DE. Mortality regardless of exposure interval was 59% at 1.50 g kg -1 of DE and 75% at 2.00 g kg -1 of DE.