Multifactored logistic models were developed for chlorpyrifos and cyfluthrin formulations based on mortality data from laboratory studies with the German cockroach, Blattella germanica (L.). Insecticides were applied to stainless steel surfaces and aged at three different temperatures (23, 30, and 37 degrees C) and two levels of relative humidity (40 and 70%). After the insecticides dried, the treated panels were placed opposite plywood panels to simulate a crack and crevice application. At appropriate aging times, treated panels were removed from environmental chambers for bioassay. The combined effects of high temperature, high humidity, and aging of residues caused the greatest decline in cockroach mortality for chlorpyrifos. Increasing temperature and aging of residues resulted in decreased cockroach mortality for cyfluthrin formulations; however, mortality was greater than 87% for all formulations through 84 d. Information from this study can be incorporated into integrated pest management programs for German cockroaches.
Residual effectiveness of insecticides was compared for two treatment methods at various sites within two commercial kitchens. For all sites and insecticides, German cockroach, Blattella germanica (L.), mortality was greatest for treatments of cracks and crevices than for treatments of exposed surfaces. Mortality at the dishwashing site was lower than at all other sites. We attributed reduced mortality at the dishwashing site to a higher vapor pressure deficit. Mortality and the amount of insecticide residue recovered from treated surfaces were closely correlated. These data demonstrate that careful placement of residual insecticide treatments will influence their effective longevity.
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