Residual efficacy of blatticides applied to surfaces contaminated with German cockroach (Dictyoptera : Blattellidae) feces

Crack-and-crevice treatments were simulated in the presence and absence of German cockroach [Blattella germanica (L.)] feces to evaluate its effect on insecticide efficacy toward the German cockroach. The LT50 of German cockr oaches exposed to 0.39 mug of cypermethrin/cm(2) (Demon EC formulation) on glass Mason jars was 26 min. The LT,increased 2.5- and 4.5-fold when Demon EC was mixed with 123 and 184 mg of cockroach feces, respectively. The pres ence of German cockroach feces increased the LT50 2.5-fold in Dursban EC (c hlorpyrifos) and 1.2-fold in Baygon EC (propoxur). Longevity experiments wi th 3 lambda -cyhalothrin formulations in the presence of German cockroach f eces resulted in significant decreases in insecticide efficacy. Feces reduc ed the performance of Commodore WP (lambda -cyhalothrin) by 12.5, 35, 55, a nd 91.5% on days 0, 10, 20, and 30, respectively. Initial reductions in eff icacy were observed for the Demand CS (lambda -cyhalothrin) and Karate (lam bda -cyhalothrin) formulations when in the presence of German cockroach fec es.