Pesticide‐mediated trophic cascade and an ecological trap for mosquitoes

Abstract

Broad-spectrum pesticides can have immediate toxic effects both on target pest species and on non-target species. They may also have positive residual effects on mosquitoes after pesticide degradation, by altering the community structure, that is, by reducing abundances of mosquito competitors and predators, and via a trophic cascade, which may increase food resources for mosquito larvae. Alternatively, if a pesticidemediated trophic cascade results in toxic or inedible algae, the pesticide can act as an ecological trap for some taxa by attracting oviposition in sites where algae are abundant but unsuitable. The present study assessed mosquito oviposition habitat selection, mosquito larval performance, and community structure alterations after applications of various pesticides. The experiment was conducted in outdoor mesocosms assigned to one of four treatments: (1) control, no pesticides; (2) Bacillus thuringiensis var. israelensis (Bti), a narrow-spectrum bacterium well known for its larvicidal activity on mosquitoes and other dipterans; (3) temephos, an organophosphate mosquito larvicide with community-wide spectrum effects; and (4) pyriproxyfen, a pyridine-based insect growth regulator (IGR) class with wide-spectrum effects. Soon after pesticide application, Culex pipiens oviposition was highest in the control pools. Invertebrate species richness and abundance were strongly reduced in the broad-spectrum pesticide treatments (temephos and pyriproxyfen) when compared to control. One month after pesticide application, Cx. pipiens oviposition was highest in the pyriproxyfen-treated pools, although larval survival remained lowest in the pyriproxyfen-treated pools. Our results suggest that pyriproxyfen causes a chemically mediated trophic cascade and provides an ecological trap, that is, attracting mosquito oviposition due to an altered community structure, but causing high mosquito larval mortality.

Effect of desiccation on mosquito oviposition site selection in Mediterranean temporary habitats

“…However, in some specific cases, the mosquito Aedes aegypti will preferentially oviposit in habitats in which the predator Toxorhynchites theobaldi and dead conspecific larvae are present, as the ovipositing females are attracted by increasing bacterial abundance due to dead larvae (Albeny‐Simões et al ., ) Increasing the amount of food increases mosquito oviposition (Blaustein & Kotler, ). Pulsed disturbances of larval mosquito sites can have an immediate negative effect on mosquitoes but can also favour mosquito oviposition during the post‐disturbance recovery period due to the alteration of community structure (Duchet et al ., , ). Indeed, Duchet et al .…”

“…Indeed, Duchet et al . (, ) showed that altered communities become attractive to gravid mosquitoes searching for oviposition sites when the disturbances decrease the abundance of mosquito antagonists but increase mosquito food resources. In our study, the disturbed pools, and more specifically the long‐drought pools, had more food resources and fewer mosquito larvae competitors, making the pools more attractive for C. laticinctus , reflected in an increase in mosquito oviposition.…”

Discovery and exploitation of a natural ecological trap for a mosquito disease vector

“…Our findings demonstrate that certain leaf litter types offer potential for the development of novel mosquito control strategies. The approach used here of attract-and-kill has been used for decades to control agricultural and forest pests but remains underexplored for arthropod vector species [22,65], and has the potential to yield an integrated vector management tool that may enhance the efficacy of and reduce the need for insecticide use. Future research should assess the duration of efficacy of leaf litter-derived attractants and toxins, including whether further ageing of the ecological trap treatment continues to attract mosquitoes [30] and whether its deleterious effect on mosquitoes may diminish over time, as well as potential dose-dependence of the attractant properties of leaf detritus [31].…”

“…For example, pyriproxyfen-treated pools act as an ecological trap for Cx. pipiens, associated with high oviposition rates yet low survival to adult emergence [22], although the mechanisms that explain the attractiveness of this trap and how this habitat yielded poor mosquito survival remain unexplored.…”

Toxic Effects of Pesticides on Humans, Plants, Animals, Pollinators and Beneficial Organisms

“…They are harmful to all organisms and pollute our surroundings. Broad-spectrum pesticides control a wide range of pest organisms [15], they can be immediately toxic for both target and non-target species [16]. Narrow spectrum pesticides control a particular of pest organisms [17].…”