Abstract:
Background: Although many mosquito species develop within agricultural landscapes where they are potentially
exposed to agricultural chemicals (fertilizers and pesticides), the effects of these chemicals on mosquito biology
remain poorly understood. This study investigated the effects of sublethal concentrations of four agricultural
chemicals on the life history traits of Anopheles arabiensis and Culex quinquefasciatus mosquitoes.
Methods: Field and laboratory experiments were conducted to examine how sublethal concentrations of four
agricultural chemicals: an insecticide (cypermethrin), a herbicide (glyphosate), and two nitrogenous fertilizers
(ammonium sulfate and diammonium phosphate) alter oviposition site selection, emergence rates, development
time, adult body size, and longevity of An. arabiensis and Cx. quinquefasciatus.
Results: Both mosquito species had preference to oviposit in fertilizer treatments relative to pesticide treatments.
Emergence rates for An. arabiensis were significantly higher in the control and ammonium sulfate treatments
compared to cypermethrin treatment, while emergence rates for Cx. quinquefasciatus were significantly higher in
the diammonium phosphate treatment compared to glyphosate and cypermethrin treatments. For both mosquito
species, individuals from the ammonium sulfate and diammonium phosphate treatments took significantly longer
time to develop compared to those from cypermethrin and glyphosate treatments. Although not always significant,
males and females of both mosquito species tended to be smaller in the ammonium sulfate and diammonium
phosphate treatments compared to cypermethrin and glyphosate treatments. There was no significant effect of the
agrochemical treatments on the longevity of either mosquito species.
Conclusions: These results demonstrate that the widespread use of agricultural chemicals to enhance crop
production can have unexpected effects on the spatial distribution and abundance of mosquito vectors of malaria
and lymphatic filariasis.
