Suppression of German Cockroach (Orthoptera: Blattellidae) Populations with Cypermethrin and Two Chlorpyrifos Formulations1

Cypermethrin and two new chlorpyrifos formulations (Dursban LO and ME) were evaluated in the laboratory and field to determine effects on German cockroaches, Blattella germanica (L.). Initially, continuous exposure of adult males on cypermethrin- or chlorpyrifos-treated surfaces for 24 h resulted in total mortality of susceptible cockroaches. Dursban LO was less effective than the ME formulation 2 wk after treatment. Multiresistant cockroaches were more difficult to kill with both chlorpyrifos formulations, but cypermethrin killed 100% of both strains within 30 min. In modified choice arena tests, cypermethrin killed 100% of German cockroaches (susceptible and multi resistant). Chlorpyrifos applied as a micro emulsion (Durban LO) and as a micro encapsulated (Durban ME) formulation resulted in 92% and 95% mortality of susceptible cockroaches and 81% and 39% mortality of resistant cockroaches, respectively. Weekly sampling of populations demonstrated that chlorpyrifos (Durban LO) resulted in significantly fewer cockroaches per harbor ager than untreated controls, whereas chlorpyrifos (Durban ME) results were variable. Field evaluations resulted in percent reductions of 91% for cypermethrin, 66% for chlorpyrifos (Durban ME), and 15% for chlorpyrifos (Durban LO) at 4 wk after treatment.