Studies conducted using laboratory and field bioassays showed that cypermethrin (b = −1.691) had a significantly (P < 0.05) higher and longer residual action at 7,14,21 and 28 days after application than did fenvalerate (b = −2.28) and permethrin (b = −1.871) against Dysdercus fasciatus Sign, and D. nigrofasciatus Stal. when coefficient regression analyses were performed. Residual action of fenvalerate and permethrin was regarded as being identical over the same experimental period in the field since their regression coefficients were not significantly (P > 0.05) different from each other.
It was also shown by these studies that the effective interval between applications was 21 days for cypermethrin and 14 days when fenvalerate and permethrin were applied. This finding has important practical implications in the adoption of an integrated approach aimed at minimizing damage to cotton by D. nigrofasciatus.
