rapid elimination of german cockroach, blatella germanica, by fipronil and imidacloprid gel baits

background: baits have become popular and effective formulations against urban insect pests. compared with re­sidual sprays toxic gel baits are used more and more frequently to control urban cockroach populations. the aim of this study was to investigate the usage of two commercially available fipronil and imidacloprid gel bait formulations against blattella germanica field infested in iran. methods:  the study was carried out in an urban area at tehran from march 2004 to september 2005. the 0.05% fipronil and 2.15% imidacloprid gel baits were placed continuously in 3 residential german cockroach infested units. pre- and post-treatment cockroach density was assessed by visual count method. results: pre- and post-treatment visual count of cockroaches in treatment and control areas, and percentage reduc­tion in cockroach density in treatment areas in comparison to control areas was showed that density reduction was increased with the 0.05% fipronil and 2.15% imidacloprid gel baits in treated areas from 1st to 9th week in compari­son to control area. after 60 days, german cockroaches eliminated completely from these areas. conclusion: these results show that fipronil and imidacloprid gel baits are highly effective in field german cock­roach infested after insecticide spraying control failure german cockroach infested fields where spraying  of pyrethroid insecticides failed to control the situation and confirm previous  reports stating that avermectin and hydramethylnon are more effective than conventional insecticides in baits against cockroaches. therefore, fipronil and imidacloprid gel baits are appropriate candidates for controlling german cockroach infested dwellings in iran where control with other insectices failed because of resistance.