The impact of the locust control insecticide fipronil on termites and ants in two contrasting habitats in northern Australia

Termites and ants are key ecosystem engineers and nutrient re-cyclers. Extensive spraying of insecticidespresents a hazard to these insects. Using a control-treatment paired design comprising 3 replicate pairs ofplots per soil type, we quantified the impact of fipronil on termite consumption of cardboard and woodbaits, termite repair of deliberately damaged mounds as well as ant community composition and abundancein two different habitats (black vertisol and red kandosol soil) when applied aerially at a dose raterecommended for locust control in Australia. The studywas conducted from 2006 to 2008. The diversity oftermites and ants was higher and side-effects were more pronounced on kandosol than on vertisol soil.Overall termite consumption of cardboard baitswas significantly greater in unsprayed than in sprayed plotswhile losses were significantly greater in only one (vertisol) or two (kandosol) sprayed plots, respectively,compared to paired unsprayed plots. In the first year, termite consumption of wood baits was generallysignificantly greater on unsprayed than on sprayed kandosol while only marginally significant onunsprayed vertisol. Again, losses were significantly greater in one (vertisol) and two (kandosol) sprayedplots, respectively, compared to paired unsprayed plots. Overall termite consumption of wood baits wassimilar among plots in the second year post-spray although consumption remained significantly depressedin one pair of sprayed plots in each habitat. The capacity of the mound-building termite, Drepanotermesrubriceps (Froggatt) unique to kandosol, to repair damaged mounds was significantly reduced by fipronil.Furthermore, colonies of Iridomyrmex greensladei Shattuck, an ant species associated with mounds of D.rubriceps, were not re-located five months post-spray. Ant communities were also adversely affected. Onvertisol, species richness and relative abundance were similar among treatments, but significantly fewerspecies were caught in one individual sprayed plot. In contrast on kandosol, species richness and relativeabundance were significantly reduced by fipronil. A drop in species richnesswas observed in all and a dropin relative abundance in two sprayed plots. On vertisol, abundances of two species were significantly lowerin sprayed than in paired unsprayed plots. Likewise on kandosol, abundances of five species were significantlyreduced in sprayed plots, and one species was not caught at all. The weight of evidence of ourfindings indicate that fipronil, even at a low rate, will have substantial adverse impacts on the diversity andactivity of termites and ants, especially if applied within one to two years of earlier applications.