Comparison of Contact Toxicity of Three Formulations of Lambda- cyhalothrin against German Cockroach First- instar Nymphs, Blattella germanica (L.) (Blattaria: Blattellidae)

German cockroach، Blattella germanica (L.) is a major worldwide household insect pest. Cockroaches play an important role as mechanical vector agents of pathogens. Also، their secretions act as main allergens of allergic diseases like asthma. The use of various formulations of conventional insecticides remains an integral part of pest management programs for the German cockroach. Contact toxicity of three commercial formulations of lambda-cyhalothrin including wettable powder (ICON® 10 WP)، microcapsule (DEMAND® 10 CS) and emulsifiable concentrate (ICON® 5 EC) were examined against first instar nymphs of B. germanica. Experiments were conducted at 27±2 ºC، 60±10% R. H and a photoperiod of 12:12h (L: D). Six concentrations of each formulation were assayed by ten replications. The mortality of nymphs was increased as consequence of rising the concentrations. The WP formulation had the most effectiveness and its LC50 value was 4. 99 mg ai. m-2. The CS and EC formulations attained LC50 values of 5. 81 and 6. 98 mg ai. m-2، respectively. The results demonstrated that the WP formulation had highest potential for control of the German cockroach.