Sublethal effects of insecticides on the reproductive success of the Tsetse species Glossina pallidipes and G. m. morsitans

Abstract

Female Glossina pallidipes Austen and G. m. morsitans Westwood (Diptera: Glossinidae) were treated with deltamethrin or pyrethrum extract through topical application or by exposure to cloth or glass treated with the same insecticides. Reproductive performance was assessed in terms of survival, pupae number and viability and reproductive deformities and abnormalities within the reproductive systems including abortions. Survival and fecundity of treated flies were significantly reduced (P<0.001). Pupae were small, mostly non-viable, and were arrested at various stages of development. Abortions of egg and all stages of larvae were observed in pregnancy cycles 1-7 following insecticide treatment. Various concentrations ranging from 1-1014 nanograms per micro litre (ng/μL) of insecticide in redistilled acetone topically applied (1μ/fly) on the dorsal thorax of the females, 24 hr after their previous blood meal, resulted in both insecticides in various concentrations causing reproductive abnormalities in both species, including egg reabsorption after ovulation. The sublethal effects were observed to prevent ovulation altogether in some of the flies, which implies effects on the reproductive performances and control strategies for tsetse flies. Sublethal doses could impact negatively on beneficial organisms in the environment where tsetse flies occur mainly riverine, woodlands and forest ecosystems.