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Simple Summary: Natural insecticides are currently given high priority in Integrated Pest Management (IPM) protocols. To this end, diatomaceous earth (DE) has gained a lot of attention as an environmentally friendly alternative to conventional insecticides that can successfully repel and control a diverse variety of the most important stored-product insect pests, such as the species Sitophilus, Rhyzopertha, Tribolium, and others. However, most published research about the DEs' insecticidal efficacy has been conducted in simplistic short-term laboratory experiments, excluding the evaluation of the persistence of such ingredients in grain applications. In this study, we evaluated two different DE formulations derived from a single deposit from Greece, when applied in wheat and maize against two primary stored-product insect pests, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). Based on the results, the DE application was effective and persistent as a grain protectant against major stored-product insects for a storage period of six months. This study provides more evidence for the successful utilization of these natural insecticides for long-term protection of stored products from insect infestations, as an alternative to residual insecticides and fumigants that are commonly used in stored-grain protection systems or as part of integrated pest management (IPM) strategies. We evaluated the persistence and efficacy of two different, in granulometry and content of diatoms, diatomaceous earth (DE) formulations (i.e., DE5 and DE6), against two major beetle species of stored products, i.e., Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). The formulations were applied as powders in soft wheat and maize in two doses of 500 and 1000 mg kg−1 (ppm). Samples of the treated grains were taken on the day of application and every 30 days until completion of the six-month period of storage. Adults of S. oryzae and R. dominica were exposed to the treated grains at 25 °C and 55% relative humidity, and the mortality was measured after 7, 14, and 21 days of exposure. Rhyzopertha dominica survival was not affected by any combination of DE formulation, dose, and commodity. Contrariwise, the DEs caused significant adult mortality of S. oryzae, in most of the cases tested. We observed that DE6 was equally effective in both wheat and maize, and no considerable variations were observed in S. oryzae mortality during the 6-month experimental period. Furthermore, DE6 was more effective against S. oryzae than DE5, a difference that could have potentially contributed to the variations in the diatom granulometry between these two DEs. Thus, a DE treatment of 1000 ppm was shown to provide long-term protection of wheat and maize against S. oryzae, but this is strongly dependent on the DE formulation, commodity, and insect species. Overall, such natural resource-based inert silicaceous deposits could be used with success in stored-product protection with only some minor modifications, such as sieving and drying of the raw deposit. [ABSTRACT FROM AUTHOR]

Simple Summary: Insecticides are currently the most effective method to control stored product insect pests worldwide. However, insecticide resistance poses a continuous threat to the viability of these management tools and thus, on food availability. Since there is very limited information available on the existence of resistant/tolerant insect populations in Greece, the objective of our study was to investigate the tolerance status of insect populations sampled from Greek warehouses and silos to a wide range of insecticides. According to our data, all field-collected insect populations indicated different patterns of tolerance, suggesting the occurrence of possible resistance to widely used insecticides. Our findings can be used for the reduction of the cases of control failures by revising the current pest management practices followed by Greek farmers and operators in stored product protection. The protection of stored products from insect pests is mainly based on suppressive methods by using contact and gaseous insecticides, globally. Following their continuous and improper use, insecticide resistance has been observed in several major insect species and pose a continuous threat to the sustainability of a wide range of active ingredients that are currently in use in stored product protection. In the present work, on-site samplings of insect populations were carried out in local warehouses containing different types of cereals. The collected insects, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) and Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), were reared under laboratory conditions to determine tolerance/resistance to widely used insecticides, using different diagnostic protocols. Laboratory populations of the same species were also examined for comparative purposes. Adult knock down and mortality of all populations indicated different patterns of tolerance to phosphine, deltamethrin, cypermethrin, and pirimiphos-methyl. In many cases, the recommended label doses were not able to completely control some of these populations, regardless of their origin, i.e., field-collected or laboratory. The results of the present work underline the importance of population on the efficacy of insecticides that are currently in use in stored product protection. [ABSTRACT FROM AUTHOR]