l-ascorbic acid provides a highly effective and environmentally sustainable method to control red imported fire ants

The red imported fire ant, Solenopsis invicta Buren, is a serious agricultural and public health pest in its introduced range. Several natural products have been tested to replace synthetic insecticides for the novel, economically feasible and environmentally friendly control of this pest. No information is available on the toxicity of vitamins to red imported fire ants. This study examined the effects of l-ascorbic acid (vitamin C) on the survival and behavior of red imported fire ants. In a toxicity assay, l-ascorbic acid (l-AA, vitamin C) appeared to be the most toxic vitamin to S. invicta and caused significantly higher mortality of S. invicta than the control and other tested vitamins. Concentration- and exposure time-dependent mortality of ants was observed after feeding on different concentrations of l-AA. S. invicta equally preferred l-AA and sucrose solution and rapidly transferred l-AA by workers. Significant adverse effects on the necrophoric, recruiting and foraging behavior of this pest insect were observed after feeding on l-AA. The walking speed of l-AA-fed ants was significantly reduced; however, we observed no significant difference in mortality of ants during group aggression assays. When we examined the presence of l-AA in the hemolymph and excretion, unlike in the normal control, more l-AA was observed in the hemolymph of the workers that ingested 0.05/0.1 g/ml of l-AA solution after 48 h. However, there was no significant difference in the concentration of l-AA in the excretion. This study demonstrated that l-AA has negative effects on S. invicta and can be used as baits to provide a highly effective and environmentally sustainable method to control red imported fire ants.