Entomopathogenic Nematode Steinernema rarum and its Symbiotic Bacterium against Fire Ants (Solenopsis sp.) under Laboratory Conditions

The genus Solenopsis comprises approximately 191 species, commonly known as fire ants. These ants are highly aggressive when the colony is disturbed and can cause accidents due to their stings. In addition, they cause economic losses in agriculture by hindering manual harvesting, feeding on crops, and establishing mutualistic relationships with sap-sucking insects. Therefore, there is considerable interest in the development of new and effective methods and products for the control of these insects. The aim of this study was to evaluate the activity of the entomopathogenic nematode Steinernema rarum and its symbiotic bacterium against fire ants (Solenopsis invicta) under laboratory conditions. To assess nematode activity at different concentrations (5, 50, 150, and 300 IJs per insect), as well as the effects of the symbiotic bacterium of S. rarum and its secondary metabolites (SM), each treatment was applied separately to different ant developmental stages (larvae, pupae, workers, and winged forms) maintained in Petri dishes. In addition, a microcolony experiment was conducted, consisting of ten workers, five larvae, five pupae, and one winged form per dish. The results demonstrated that all treatments with nematodes, the bacterium, and its metabolites caused mortality in ants, ranging from 10 to 100% depending on the developmental stage and treatment. These findings highlight the potential of entomopathogenic nematodes and their symbiotic bacteria for the control of fire ants. However, further studies are required to develop suitable formulations and management strategies for future field applications.