The number of feces of the intoxicated German cockroaches, Blattella germanica, and delayed effects of hydramethylnon gel bait in the laboratory condition

Small amounts of hydramethylnon were dispersed in a test arena or inside of harborages by the German cockroaches, Blattella germanica, following their feeding on gel bait with this active ingredient. Water, cockroach carcasses and their feces were also contaminated with hydramethylnon. When fresh colonies of the German cockroaches were exposed to the contaminated arena or harborages, most died within 20 days; mortality from exposure to water, carcasses, and feces was less than in the contaminated arena or harborages. The amount of feces produced by cockroaches feeding on hydramethylnon was less than what cockroaches normally produce. Bait dyed with red color (Pamo acid pyribinium) provided evidence of cockroaches carrying small amounts of bait to the inside of harborages and the floor of the test arena. Delayed action of hydramethylnon bait against the German cockroaches might be the result of exposure to contaminated harborages or the surface of the foraging area.