Fungus promises biological control of Argentine ants

For the first time, scientists have successfully tested a biological control agent against the Argentine ant (Linepithema humile), one of the worst invasive species in the world. The research, conducted in Argentina, demonstrated that the Li053 strain of the entomopathogenic fungus beauveria bassiana caused mortality of over 80% in ants in just two to five days.

Argentine ants form supercolonies that span continents. They threaten native biodiversity, protect plant pests and invade apiaries, destroying hives and forcing bees to abandon their colonies. They also damage irrigation systems by piercing hoses, which directly affects agricultural production.

Chemical control, which until now had been the main strategy, has proven to be ineffective in the long term. It requires constant reapplication, is expensive and impacts non-target organisms. Despite the urgency for sustainable alternatives, no biological option has been tested against this species.

The team led by Patricia Folgarait and Daniela Goffré isolated six strains of fungi from dead ants collected in nature reserves in the province of Buenos Aires. Behavioral aggression tests confirmed that the samples came from different colonies. The scientists then applied the fungi to workers from four supercolonies using three methods: topical application, spraying, and immersion.

The Li053 strain of B. bassiana stood out in all tests. Regardless of the inoculation method or the origin of the ants, it caused high mortality, with LT50 between 2 and 5 days. Analysis of the cadavers confirmed infection by the fungus in up to 92% of cases. Additional tests revealed that higher concentrations of spores increased lethality and reduced time to death, with LC50 estimated at 1 x 10⁶ conidia/mL.

The other isolated fungi showed varied results. Some strains caused high mortality, but with low recovery of the fungus in the cadavers, suggesting interference from natural agents or unidentified causes. Strain Li053, on the other hand, maintained consistent performance.

The authors highlight the strain's potential as a biological control tool. As it is a native species, B. bassiana Li053 poses reduced risks to local wildlife and agriculture. Furthermore, the use of natural enemies allows for safer, more sustainable and targeted solutions with less environmental impact.

Next steps involve field testing, commercial formulations and ecological safety assessments.

More information at doi.org/10.3390/insects16070677