Effects of Two Temperature Storage Regimes on the Efficacy of 3 Commercial Gel Baits against the German Cockroach, Blattella germanica L. (Dictyoptera: Blattellidae)

Background: To compare the effectiveness of 3 commercial gel bait formulations containing fipronil (Goliathã Cockroach Gel 0.05% AI), chlorpyrifos-A (Clean Baitã Gel, 2% AI), and chloropyrifos-B (Serpaã Gel 2% AI) against German cockroaches (Blattella germanica) when stored at 23°C and 30° C after treatment. Methods: Laboratory bioassays consisted of placing groups of fifteen cockroaches (a random combination of adult, mixed sex and large nymphs-stage 6) into a 5 L cylindrical plastic container with one drop of product (avg 0.10 g ± 0.01 g) applied to a 76 mm x 26 mm glass microscope slide affixed to the bottom of each container (one product tested per container). Cumulative mortality was assessed at 6 h, 1, 2, 3, 4, and 5 d after application. To determine the further effects of storage temperature after treatment on residual activity of the gels, a drop of each product was applied to separate glass microscope slides and stored at either 23º C (warm) or 30º C (hot) under dark conditions for 0, 1, 7, 14, 30, 45, 60 and 90 d after application. Results: Freshly applied baits (day 0) containing fipronil provided complete cockroach mortality (100%) within 5 d whereas chloryrifos-A and chlorpyrifos-B provided »72% and 88% mortality, respectively. Generally, cockroach mortality was greater when gels were stored at 30°C compared with 23º C. Conclusion: The fipronil gel formulation proved to be as efficacious as the chlorpyrifos gels and in some instances surpased the latter formulations depending on storage time and temperature by providing »90% mortality at 90 d post treatment.