Study shows single insecticide application can kill 3 cockroach g...(lso died. Both statistics were taken 72 ...)

Mortality of cockroaches at the fourth level, three times removed from the original insecticide dose, was not any higher than for those insects that hadn't been exposed to the insecticide through any method, said Buczkowski, director of the Purdue Industrial Affiliates Program.

Adult German cockroaches are a shiny orangey tan and about half an inch long. The youngest nymphs, as used in this study, are called first instars and are one to five days old. Nymphs go through five stages on their way to adulthood.

In addition to attracting more cockroaches with the pheromones in their feces, the insects can cause other problems.

"Cockroaches molt their skin as they go from one nymph stage to the next, and there is a huge accumulation of the skin left in the areas where they live," Buczkowski said. "The dead skin becomes airborne and causes allergies and asthma. It's really the biggest problem with cockroaches."

Buczkowski plans to investigate tertiary kill with other cockroach baits and possibly look at horizontal transfer of insecticides in natural settings rather than just in the laboratory.

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