Synthetic and Natural Insecticides: Gas, Liquid, Gel and Solid Formulations for Stored-Product and Food-Industry Pest Control

SIMPLE SUMMARY: Currently, there is great global research interest in the use of novel methods of protection against agricultural, storage, and urban pests, particularly in the use of botanical substances and nontoxic materials. To ensure efficacy and safety, botanical and synthetic insecticides must be properly formulated and delivered in a species-specific way to their pest targets. The wide diversity of pests and environments—globally occurring at farms and food industry facilities—has inevitably resulted in a massive proliferation of application formulations and approaches. Although there are excellent summaries on particular aspects of the usage of synthetic and botanical pesticides, a general overview of application formulations on stored-product and food-associated pests is not currently available. This review provides an inventory of current and historical pesticide formulations. Its structure follows the traditional insecticide categorization based on four physical formulation types: gas, liquid, gel/foam, and solid. The review documents renewed research interest in optimizing traditional methods, such as insecticide baits, aerosols, sprays, fumigants, and inert gases, as well as the feasibility of integrating these methods with natural insecticides and physical measures (e.g., low temperatures) as combined application approaches. Several emerging technologies of pesticide formulations have been identified; they include electrostatic dusts or sprays, nanoparticles, hydrogels, inert baits with synthetic attractants, biodegradable cyanogenic protective coatings of grain, and RNA-based gene silencing compounds encapsulated in baits. Traditional and new formulations of natural compounds, including inert dust (diatomaceous earth) and botanicals (essential oils), have been considered as non-synthetic chemical control solutions for organic food production in developed countries and as affordable home-made insecticides in developing countries. The authors hope that the general coverage and extensive photographic documentation will make this review useful not only for scientists but also for students and practitioners. ABSTRACT: The selective application of insecticides is one of the cornerstones of integrated pest management (IPM) and management strategies for pest resistance to insecticides. The present work provides a comprehensive overview of the traditional and new methods for the application of gas, liquid, gel, and solid physical insecticide formulations to control stored-product and food industry urban pests from the taxa Acarina, Blattodea, Coleoptera, Diptera, Hymenoptera, Lepidoptera, Psocoptera, and Zygentoma. Various definitions and concepts historically and currently used for various pesticide application formulations and methods are also described. This review demonstrates that new technological advances have sparked renewed research interest in the optimization of conventional methods such as insecticide aerosols, sprays, fumigants, and inert gases. Insect growth regulators/disruptors (IGRs/IGDs) are increasingly employed in baits, aerosols, residual treatments, and as spray-residual protectants for long-term stored-grain protection. Insecticide-impregnated hypoxic multilayer bags have been proven to be one of the most promising low-cost and safe methods for hermetic grain storage in developing countries. Insecticide-impregnated netting and food baits were originally developed for the control of urban/medical pests and have been recognized as an innovative technology for the protection of stored commodities. New biodegradable acaricide gel coatings and nets have been suggested for the protection of ham meat. Tablets and satchels represent a new approach for the application of botanicals. Many emerging technologies can be found in the form of impregnated protective packaging (insect growth regulators/disruptors (IGRs/IGDs), natural repellents), pheromone-based attracticides, electrostatic dust or sprays, nanoparticles, edible artificial sweeteners, hydrogels, inert baits with synthetic attractants, biodegradable encapsulations of active ingredients, and cyanogenic protective grain coatings. Smart pest control technologies based on RNA-based gene silencing compounds incorporated into food baits stand at the forefront of current strategic research. Inert gases and dust (diatomaceous earth) are positive examples of alternatives to synthetic pesticide products, for which methods of application and their integration with other methods have been proposed and implemented in practice. Although many promising laboratory studies have been conducted on the biological activity of natural botanical insecticides, published studies demonstrating their effective industrial field usage in grain stores and food production facilities are scarce. This review shows that the current problems associated with the application of some natural botanical insecticides (e.g., sorption, stability, field efficacy, and smell) to some extent echo problems that were frequently encountered and addressed almost 100 years ago during the transition from ancient to modern classical chemical pest control methods.