Laboratory evaluation of several insecticides as feeding inhibitors against the German cockroach, Blattella germanica (L.)

The bait tablets containing 0.1 or 1% propoxur, carbary, dieldrin, DDT, BHC, lindane, naled, fenthion, malathion, fenitrothion, diazinon, or trichlorfon showed repellency more or less against German cockroaches, when tested with the similar tablets containing no insecticide. Propoxur, naled, and BHC were highly repellent, whereas trichlorfon was little. The consumption of the trichlorfon-bait by an alive cockroach per day was much greater than that of the propoxur-bait on the first day of the experiment, whereas the consumption of the nonpoison bait kept as the control increased later on. Many cockroaches (more than 10%) could survive on the bait containing 0.5% propoxur and 20% boric acid, although the bait containing only the latter would have given the complete mortality. The strong initial repellency of propoxur in the bait would be responsible for the decreased mortality of the cockroaches. The consumption by the living cockroaches of both poison (propoxur and trichlorfon) and nonpoison baits decreased as the tests progressed. The similar trend was observed when we treated the cockroaches with the sublethal doses of the poisons. Satisfaction of their appetite or loss of their appetite by the intoxication, or both are the possible causes for the decreased bait consumption.