# Surface Application of Different Insecticides Against Two Coleopteran Pests of Stored Products
## 1 Introduction  
Stored-product insects represent major threats to food safety and quality in grain storage and food processing facilities worldwide. These pests are responsible for significant quantitative and qualitative losses, including contamination with exuviae, feces, and other biological residues [1, 2, 3, 4]. According to FAO estimates, insect infestations can account for up to 10-20% of global stored-product losses, particularly in developing countries [5]. These insects thrive in various ecological niches within storage and processing facilities and are known for their adaptability and persistence across a range of commodities [6, 7, 8, 9]. For instance, in the case of _Lasioderma serricorne_ (F.) (Coleopterara: Anobiidae), it has been found that infestations can severely affect not only tobacco products but also a wide range of dried stored goods, including herbs, spices, and cereals, often leading to product rejection due to contamination [6, 10]. Meanwhile, _Tribolium castaneum_ ([PERSON]) (Coleopterara: Tenebrionidae)is recognized as one of the most economically significant secondary colonizers, particularly in processed cereal products and flour-based commodities, where its persistence and resistance to insecticides complicate control efforts [11; 12; 13]. _Sitophilus granularus_ and _Sitophilus_ _oryzae_ (L.) (Coleoptera: Curculionidae), primary internal feeders of intact grain kernels, are equally important, causing substantial weight loss and grain damage, especially in bulk-stored wheat, leading to reduced nutritional and market value [14; 15]. A common and long-standing approach to insect management in stored commodities is the direct application of insecticides to the grain. Such applications, typically in the form of protectants or admixtures, have demonstrated substantial efficacy against key pest species [16; 17; 18]. This strategy remains a cornerstone of post-harvest protection due to its capacity to suppress pest populations over extended storage intervals [14; 17]. A broad spectrum of insecticides, including pyrethroids, organophosphates, and spinosyns, has shown high effectiveness when applied directly to stored grain [18; 19; 20]. For example, applications of alpha-cypermethrin and spinosad have proven effective in controlling _Rhyzopertha dominaica_ ([PERSON]) (Coleoptera: Bosticthidae) and _Cryptolestes ferrugineus_ ([PERSON]) (Coleoptera: Laemophloeidae) on wheat [21]. Furthermore, pirimiphos-methyl has been reported to exert high efficacy against larvae of _Tribolium confusum_ Jacquelin [PERSON] (Coleoptera: Tenebrionidae) and _Ephestia kuehniella_ Zeller (Lepidoptera: Pyralidae) when used on treated packaging materials [1]. Nevertheless, despite the efficacy of these treatments, their continued use raises legitimate concerns regarding pesticide residues on food products [2; 22]. Residual concentrations may exceed maximum allowable levels, posing potential risks to human health and reducing product acceptability in international markets [2; 17]. Additionally, sustained use of grain-applied insecticides contributes to the emergence of resistant pest populations, further limiting control options over time [14; 16; 23]. Increasing attention has been directed toward alternative approaches that limit direct exposure of insecticides to the commodity. Among these, the application of insecticides to structural surfaces such as floors, cracks, and crevices is well-established as a complementary strategy in stored-product and food industry environments [17; 24; 25]. This method, often incorporated into integrated pest management programs, enables residual protection in areas frequented by mobile insect stages while minimizing contamination risks. Previous studies have demonstrated the potential of surface treatments to control key pests under operational conditions, particularly those species that are highly mobile or cryptic in behavior [7; 23; 26].