The »tawny crazy ant« from South America (Nylanderia fulva) has been competing with other invasive ants for dominance on US soil and elsewhere for several decades. The competitors deliver an arms race in which N. fulva is often ahead: the insects can, for example, neutralize the fighting poison of the fire ants with their own secretion. The invaders usually make short work of other, less well-fortified competitors anyway, and so they cause great ecological damage if they are carried off into a previously untouched habitat.
Now, however, a remedy may have been found against the ant invaders, who are difficult to defeat: A research team reports in the specialist magazine »PNAS« about a naturally occurring pathogen from the Microsporea group, against which the ants seem defenseless. Biologists know Microsporea as cell parasites of fish or bees.
The crazy ants also seem to have their own Microsporea pathogen, report Edward LeBrun from the University of Texas at Austin and his team. The pathogen infects the fat body in the abdomen, where it forms masses of spores and inflates the insects until they die. Apparently it occurs naturally in the South American homeland of the ants. If it is carried away with the insects, it quickly causes the ant colony to collapse: 62 percent of all affected colonies disappear completely, report LeBrun and his colleagues, who have observed various ant colonies over eight years.
The cell parasite appears N. fulva to be specialized: It apparently affects neither other ants nor other arthropods. This would make it ideal as a biological weapon against the aggressive ants. LeBrun and co tested this back in 2016 in an experiment at Estero Llano Grande State Park in Texas. Many insects, scorpions, snakes, lizards and birds had already died in the ecosystem overrun by the ants. The researchers then released Microsporea-infected animals from another area in the park and lured the healthy population with hot dogs as bait. It then took a year for the microsporea to infect the healthy population as well – and after two years it collapsed completely. Today the park is once again populated by its original insect population. LeBrun’s team is now working on biologically combating the ant invaders in other sources of infection even more efficiently.