Inefficacy of essential oil-based products used as residuals for German cockroach (Blattella germanica L.) control

German cockroaches, Blattella germanica (L.) (Blattodea: Ectobiidae), remain one of the most challenging indoor pests to manage. Current pest management practices rely heavily on synthetic insecticides, but insecticide resistance has rendered many of these products ineffective. Furthermore, due to the toxicity of some synthetic insecticides, there is concern surrounding potential hazards to humans, pets, and the environment. Consequently, there is a growing demand for natural products that are effective against urban pests, including cockroaches. To address this demand, several products have been formulated with essential oils. While essential oil-based products have environmentally favorable insecticidal profiles, their effectiveness against German cockroaches, particularly their residual activity and behavioral effects, remains poorly understood. In this study, we evaluated the efficacy of commercially available essential oil-based products through both direct application and residual exposure. Further, we explored the effects of essential oil-based products on German cockroach behavior. Our results show that while essential oil-based products cause nearly 100% mortality when applied directly to German cockroaches, they are generally ineffective when tested as residuals, even when tested only 24 h after application. German cockroach behavior was impacted by some essential oil-based products, with a reduction in time spent on surfaces treated 4 h before exposure, although this behavior was generally lost when surfaces were aged for 24 h. The results of this study demonstrate the ineffectiveness of essential oil-based products used as residuals for German cockroach control. Because this species is cryptic and direct insecticide application to every individual is impractical, effective management requires residual control; therefore, treatments using these essential oil-based products are unlikely to succeed.