Cockroach connoisseurs: How contamination of insecticidal baits affects German cockroach, Blattella germanica, behavior

German cockroaches (Blattella germanica) are one of the most persistent and difficult pests to manage in urban environments, as infestations can reach massive numbers and insecticide resistance is extremely common. The prevalence of resistance to common spray-based insecticides has popularized the use of gel baits, which are highly effective and can greatly reduce liquid residual insecticide application. However, the length of time required for gel baits to eliminate infestations can cause pest control operators or unassuming homeowners to contaminate baits with a variety of different chemicals, including insecticides and cleaning products. There is a pre-existing notion that contamination of this type reduces bait efficacy and can cause treatment failure. To address this notion, we evaluated bait consumption and efficacy after contamination with a number of insecticides and common cleaning products. Many contaminants were included based on scent, mode of action, added ingredients, and ubiquity. Bait efficacy was assessed based on mortality of cockroaches exposed and consumption of the baits by those cockroaches. Assays were created using plastic arenas with water and shelter ad libitum. Contaminated baits were introduced into the arenas alongside uncontaminated inert food, and cockroaches were allowed to interact with them for seven days, with consumption and mortality assessed daily. Understanding how contamination plays a role in bait efficacy will allow pest control professionals and consumers alike to more effectively utilize baits.