Toxicity of two Pyrethroids, OMS-1998 AND OMS-1821 to the Tsetse fly, Glossina palpalis palpalis (Robineau-Desvoidy) and their Persistence in the environment
The toxicity and persistence of two pyrethroids, OMS-1998 and OMS 1821 were studied by bio-assay tests with laboratory bred Glossina p. palpalis R-D. Pieces of blue cotton fabric material (100cm x 85cm) were impregnated with 19.59mg 5% OMS-1998 and 176.47mg 25% OMS-1821 respectively. Control was treated with distilled water and all the targets were exposed to weathering conditions in the field. Two samples were cut from the targets on the first day of exposure and subsequently at two weeks intervals. Test flies were maintained-at about 24 C to 26 C and 75% to 88% relative humidity before and after experiments and were last fed a day before treatment. In the first four weeks fly mortality was 100% and knockdown was followed by death within 24 hours post treatment. There were variations in fly
mortality in the last eighth weeks but knockdown was followed by recoveries and then death at 48 hours post treatment. Female’ Glossina p. palpalis were more tolerant of both compounds than males. Both compounds have long residual longevity but
OMS-1998 proved superior in residual effect on targets and being more effective against tsetse flies.