Two University of Maine researchers were part of a team that may have stumbled upon a way to weaponize nematodes in the fight against fire ants.
They discovered that in two central Maine sites, infected nematodes carried a bacteria into ant colonies that killed the fire ants. So the scientists decided to see if the nematodes could be used as a biological control against the invasive pest.
Turns out, while there is a possibility that it could work, one of the lead professors on the study said it’s too soon to start spraying nematodes on fire ant hills in Maine.
“There is a lot of research left before nematode transmission of bacteria could be used as biological control against ants,” said lead study author Sue Ishaq, Ph.D, an assistant professor of animal and veterinary sciences at the University of Maine. “But it remains an intriguing possibility,”
The ant colonies were on Mount Desert Island and in Orono, according to the study published in the online journal iScience this past June. The nematodes or roundworms picked up a bacteria from the soil that infected their digestive tracts. When the nematodes subsequently entered the ants through one of the insect’s body cavities, they carried that bacteria right along with them.
The fire ants in Maine are the European variety. While they are not as aggressive or venomous as the red imported fire ant found in the southern United States, they will defend their colonies. The European fire ant will attack intruders in large numbers. Their stings are painful and can cause allergic reactions in some people.
Maine’s fire ants are well established in the midcoast and central areas of the state, so any method of controlling or eradicating them would be good news.
To see if infected nematodes could be unleashed in a sort of insect-version of biological warfare against the fire ants, Ishaq and her team co-leader Eleanor Groden, Ph.D, retired University of Maine professor of entomology, tried to replicate the bacteria’s path from soil to worm to ant in a laboratory setting.
In the controlled experiment, the nematodes picked up the bacteria from the supplied soil samples, but the lab nematodes did not pass along the bacteria to a new host, in this case waxworm larvae.
That, according to the study, cast a bit of doubt on the effectiveness of nematodes as a consistent carrier for infecting the fire ants with lethal bacteria.
At this point, Ishaq said, there are too many other variables that could come into play, including where the nematodes come from and local environmental conditions. In the case of the wild colonies that were killed off, only nematodes collected from Breakneck Road in Acadia National Park and from the site in Orono carried the lethal bacteria. It was not found in nematodes collected at Hulls Cove, less than half a mile from Acadia National Park.
There are many reasons that was the case, Ishaq said.
“Out in the field it could be that every once in a while you get one bacteria that under the right conditions kills the fire ants,” Ishaq said. “It could really just be serendipitous.”
It could be, she said, that it took the perfect combination of the right bacteria in the right soil infecting the nematode at the right time to effectively carry it to the ants.
“In lab experiments it could be possible to replicate that,” Ishaq said. “But it’s really tricky to make it happen reliably.”
For nematodes to be used as an effective control against fire ants, Ishaq said more study is needed, and even then it could just turn out that it was a random mutation or change in a specific bacteria that killed the ants.
“As far as weaponizing nematodes?” Ishaq said. “They just don’t seem to be that cooperative.”
Correction: The name of lead researcher Dr. Sue Ishaq was misspelled in the original version of this story. It has been corrected.