12th International Working Conference on Stored Product Protection (IWCSPP) in Berlin, Germany, October 7-11, 2018 Julius-Kühn-Archiv 463 739 Session 7 Contact Pesticides, Residual Products, and Plant Extracts Laboratory Evaluation of Turkish Diatomaceous Earths as Potential Stored Grain Protectants Sezgin Akçali 1 , Ali Arda Işikber 1* , Özgür Sağlam 2 , Hasan Tunaz 1 , Mehmet Kubilay Er 1 1 Kahramanmaraş Sütçü İmam University, Agriculture Faculty, Plant Protection Department, Avşar Campus, 46100, Kahramanmaraş, TURKEY 2 Namık Kemal University, Agriculture Faculty, Plant Protection Department, Tekirdağ, TURKEY * Corresponding Author: isikber@ksu.edu.tr DOI 10.5073/jka.2018.463.161 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. onfusum 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. Key Words: Turkish diatomaceous earth, wheat, Sitophilus oryzae, Tribolium confusum, Rhyzopertha dominica Introduction Stored products and especially grains and their by-products are the most important durable food category for human nutrition. During storage, these commodities are attacked by a numerous pests, particularly insect species, known as stored product pests, which cause very serious quantitative losses and qualitative degradations. Apart from the direct infestation per se, the presence of these pests and the substances that they produce may seriously endanger human health. In these commodities, which are also known as durable stored products, residual contact insecticides and fumigants are currently used as the main way to avoid insect infestation. Nevertheless, most of these pesticides are very toxic to mammals, and some of them leave dangerous residues on the product which may accumulate in the human body through the food chain. Moreover, most major insect species are now resistant to many of these pesticides, while some of these substances, such as methyl bromide, are extremely dangerous for both human health and the environment. Methyl bromide was thus banned by 2005 in industrialized countries according to the Montreal protocol, and it is expected to be completely withdrawn from the developing countries until 2015 (Bell 2000). Therefore, there is an urgent need to evaluate alternatives to traditional pesticides, which will have low mammalian toxicity, will be cost-effective and will be environmentally-compatible. One of the most promising alternatives over the use of traditional pesticides in durable stored products is the use of diatomaceous earths (DEs). DEs are composed by the fossil skeletons of phytoplanktons, also known as diatoms, which occur in fresh and salt water since the Eocene period