Laboratory evaluation of Turkish diatomaceous earths as potential stored grain protectants

In this study, efficacy of local diatomaceous earths (DE) collected from different regions of Turkey against stored grain insects, Sitophilus oryzae (L.), Tribolium confusum du Val. and Rhyzopertha dominica (F.), was investigated. For this purpose, biological tests were carried out at concentrations of 500 and 1000 ppm (mg DE / kg wheat) of 9 local diatomaceous earths and one commercial diatomaceous earth, namely Silicosec® as positive control at 25 ± 1 ° C temperature and 65 ± 5% relative humidity in wheat. In addition, the studies on some of the chemical and physical analysis of the tested diatomaceous earths (silicon dioxide (SiO2) ratio, particle size and adhesion rate on commodity) were also conducted. In biological tests conducted at 500 ppm concentration for 14 days of exposure in wheat the highest mortality rates (97 to 98%) of S. oryzae adults were recorded in CB2N-1, AGN-1 and BGN-1 diatomaceous earths, while the highest mortality rates of T. confusum adults were obtained from only AGN-1 and BGN-1 diatomaceous earths. In the case of R. dominica, the highest mortality rate (64.4%) was recorded only in CB2N-1 diatomaceous earth. At concentration of 1000 ppm for 14 days of exposure in wheat, 100% mortality of S. oryzae adults was observed in all tested local diatomaceous earths except FB2N-1 and Silicosec® while mortality rates of T. confusum adults ranging from % 95 to %100 were obtained in all tested local diatomaceous earths except FB2N-1, FBN-1 and Silicosec®. In the case of R. dominica adults, mortality rates ranging from 80% to 93% were recorded in CB2N-1, CCN-1 and AG2N-1 diatomaceous earths. In conclusion, laboratory bioassays indicated that CB2N-1 and BGN-1 local diatomaceous earths had high efficacy against S. oryzae, T. confusum and R. dominica adults and thus could be potential to be successfully used for controlling stored grain insect pests as a grain protectant.