Residual Efficacy of Lufenuron (Instar®), 1994

Residual effect of a new chitin synthesis inhibitor, lufenuron (Instar® 0.2 TB) was determined against three different nymphal ages of German cockroach (1-week, 3-week and 5-week) and American cockroach (1-week, 5-week and 10-week). Hardboard panels (11 × 11 cm for German cockroaches; 16.5 × 16.5 cm for American cockroaches) were sprayed with Instar® (effervescent tablet diluted in distilled water) at the recommended rate of 10 mg AI/m2. Control panels were sprayed with distilled water. The panels were then allowed to dry naturally for approximately 6 hours before being stored vertically at 27 ± 3°C and 70 ± 5% RH until the appropriate aging period. Exposure to the residues was conducted by confining the respective chosen age group insects in transparent perspex boxes (13.5 × 18 × 6 cm for German cockroach; 27.5 × 21 × 9 cm for American cockroach). The aged treated panels were then placed at one side of the box and two pieces of folded filter paper as harborages were placed at the other side. A bottle cap with a soaked cotton bung was supplied at the center of the treated panel surface so that the insects were forced to contact with the treated surface whenever they went to the water source. Twenty-five nymphs were used in each replicate and each experiment was replicated four times. The boxes were kept at the condition previously mentioned; dead insects were counted and removed daily. LT50 was determined by pooling the cumulative mortality results of four replicates and subjected to probit analysis. Mortality in control was corrected using Abbott’s formula.