Efficacy of imidacloprid and fipronil gels over synthetic pyrethroid and propoxur aerosols in control of German cockroaches (Dictyoptera: Blatellidae)

Background & objectives: Resistance amongst cockroaches has been reported to most of the sprayinsecticides apart from the problem of food contamination and inconvenience. Gel baits which canbe selectively applied have been found effective in control of cockroaches in laboratory studies butvery few field studies are available. This trial was planned to evaluate the efficacy of fipronil(0.01%) and imidacloprid (2.15%) gels over synthetic pyrethroid (0.02% deltamethrin + 0.13%allethrin) and propoxur (2%) aerosols in control of cockroaches in the field.Methods: Survey was done to find out pre-treatment density in catering establishments and housesby visual count and sticky trap methods. A total of 10 catering establishments and 10 houseshaving high cockroach infestation were selected by sampling (two catering establishments andhouses for each insecticidal treatment and two for control). Propoxur and synthetic pyrethroidaerosols were used for spraying the infested sites once only. Single application of fipronil andimidacloprid gels was used as crack and crevice treatment. Visual count method gave betterindications of cockroach infestation as compared to sticky trap method, hence, the same was followedfor post-treatment evaluation every week up to 12 weeks.Results: Synthetic pyrethroid could not bring about the desired reduction in cockroach infestationin the present study. Single application of fipronil gel was able to reduce cockroach infestation upto 96.8% at the end of 12 weeks whereas imidacloprid application resulted in 90.9% reduction andpropoxur resulted in 77.5%. However, propoxur was more effective in reducing the cockroachdensity by first week in comparison to imidacloprid and fipronil gels but its efficacy started decliningafter 8th week. Difference was found statistically significant by Kruskal-Wallis H-test.Conclusion: The study reports the efficacy of propoxur aerosol, imidacloprid gel and fipronil gelbaits for control of cockroaches.