A bacterium common in insects has been discovered in a plant-parasitic roundworm, opening up the possibility of a new, environmentally friendly way of controlling the crop-damaging pest.

The worm, Pratylenchus penetrans, is one of the "lesion nematodes" - microscopic animals that deploy their mouths like syringes to extract nutrients from the roots of plants, damaging them in the process. This particular nematode uses more than 150 species as hosts, including mint, raspberry, lily and potato.

The newly discovered bacterium is a strain in the genus Wolbachia, one of the world's most widespread endosymbiont parasites (organisms that live within other organisms). Wolbachia is present in roughly 60 percent of the world's insects, spiders and crustaceans, and also lives in nematodes (roundworms, including parasitic worms that cause illness in humans).

Dr Amanda Brown discovered the bacteria in roundworms whilst at Oregon State University. The bacteria type can cooperate with its host, or act as a damaging parasite, depending on the host’s species. In the case of the crop-pest nematode, Pratylenchus penetrans, that Brown and her colleagues studied, the bacteria-host relationship appears not to be a mutually beneficial one (though more study is needed to determine the exact nature of the relationship, according to the scientists).

Whatever the relationship, simply discovering Wolbachia in Pratylenchus penetrans opens up the potential for managing the roundworm's population via biocontrol rather than environmentally damaging chemistry; some old pesticides that are currently used are being phased out by the Environmental Protection Agency in the U.S.

"We can use what's already infecting [the nematodes] against them," the researchers speculated.

Nematode biocontrol would involve releasing Wolbachia-infected worms into farm fields whose worm populations weren't infected. From there, the scientists said, a couple of situations, both favorable to the crops, might arise:

• The bacterium could hinder the worms' ability to reproduce;
• It also might force the worm to devote energy to dealing with the bacterium, effectively distracting it from being as damaging to the crops as it otherwise would be.

Wolbachia is already being used as a biocontrol strategy in Colombia and Brazil, where infected mosquitoes are being released in an effort to control the Zika, dengue and malaria viruses. Mosquitoes are a vector for those diseases, but Wolbachia-infected mosquitoes pass the bacteria to their offspring, who lose their ability to transmit disease. the bacteria also can interfere with the mosquitoes' ability to reproduce at all.

Commenting on the breakthrough, Oregon State Professor Dee Denver said, ”We can see [how the biocontrol strategies in South America go] and learn from [them] to help our decision making on how the strategy might get deployed to control the population of plant-parasitic nematodes. One big thing with nematodes is the load. Many crops have some, but once you get above certain thresholds, fields go down and there are economic losses."

Prof Denver continued, ”There are thousands of nematode species infecting plants. Wolbachia has always been thought of as an arthropod thing, an insect thing. It was kind of a serendipitous discovery for us. We were sequencing genomes from nematodes for the purpose of understanding nematodes, and the mapping went to Wolbachia."