Drastic reduction in density of Blattella germanica and Periplaneta americana cockroaches after the application of fenitrothion and lindane in Dema, Zimbabwe

Field studies were conducted in villages near the peri urban Dema area, Seke district, Zimbabwe, in order to understand the effect of the insecticides fenitrothion and lindane on Periplaneta americana and Blattella germanica cockroaches. A total of 63, 72 and 71 rooms were used for control, fenitrothion and lindane respectively. The mean density per room for P. americana before spraying was 43.5, 42.7 and 44.1 for the control, fenitrothion and lindane respectively. The mean density per room for B. germanica before spraying was 51.4, 50.2 and 47.1 for the control, fenitrothion and lindane respectively. A reduction in population density of P. americana was 3.2%, 83.8% and 99.3% in the control, fenitrothion and lindane rooms respectively. A reduction in population density of B. germanica was 87.8% and 82.8% in fenitrothion and lindane rooms respectively. An increase of 9.9% in the control rooms was observed. The majority of P. americana cockroaches died one month post spray with fenitrothion killing 78.2% and lindane 37.4% of all cockroach collections. However, the number of dead B. germanica cockroaches was almost of the same order for fenitrothion (71.9%) and lindane (74.5%). The residual effect of fenitrothion was 3 months on both cockroach nymph species and that of lindane was 1 month. In conclusion, both fenitrothion and lindane had impact on cockroach density, and fenitrothion showed a residual effect of 3 months.