Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 13, 2000
Publication Date: N/A
Interpretive Summary: When cockroach control measures fail, insecticide resistance in German Cockroaches is often presumed to be the cause. However, it is possible that other factors may be responsible. One possibility is that the accumulation of cockroach excrement either binds or breaks down the toxicant, making it unavailable to cockroaches. Therefore, a commonly used dinsecticide application method known as crack and crevice treatment, was simulated in the laboratory to evaluate the effect of cockroach excrement found in these areas on insecticide efficacy. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in collaboration with University of Florida Scientists, found that the presence of cockroach excrement significantly decreased the efficacy of several emulsifiable concentrate insecticides (chlorpyrifos, cypermethrin, and propoxur). The efficacy of other insecticide formulations (Wettable Powder, and Capsulated Suspension) also were decreased in the presence of cockroach excrement. These results help to explain control failures when this method of insecticide application is employed. Recommendations for improving the method are suggested.
Technical Abstract: Crack and crevice treatments were simulated in the presence and absence of German cockroach feces for the purpose of evaluating its effect on insecticide efficacy toward the German cockroach, Blattella germanica (L.). The LT50 of Orlando cockroaches exposed to glass mason jars treated with 0.39 æg[AI]/cm2 Demon EC (cypermethrin) was 26 min. LT50 significantly increased 2.5- and 4.5-fold when Demon EC was mixed with 123 and 184 mg of cockroach feces, respectively. The presence of German cockroach feces increased the LT50 2.5-fold in Dursban EC (chlorpyrifos) and 1.2-fold in Baygon EC (propoxur). Longevity experiments of various lambda-cyhalothrin formulations in the presence of German cockroach feces resulted in significant decreases in insecticide efficacy through time. Feces reduced the performance of Commodore WP by 12.5, 35, 55, and 97.5% on days 0, 10, 20, and 30, respectively. Initial reductions in efficacy were severe for the Demand CS and Karate formulations when in the presence of German cockroach feces.