Auburn University plant pathologist Kathy Lawrence was a bit mystified a few years back when research in her lab revealed that soil- dwelling, crop-destroying nematodes spread significantly farther and deeper at a much faster rate than long had been assumed.

Now, five years later, another discovery by a graduate research assistant of hers is shedding new light on that earlier finding, offering the first scientific evidence that disease-causing nematodes can and do hitchhike to other parts of a field, not only on farm equipment but also on—or, rather, in — earthworms.

“What we wanted to know in this study was whether earthworms pick up nematodes as they move through the soil, whether plant-parasitic nematodes are present in earthworm castings in Alabama cotton fields and whether they’re present in the gut systems of earthworms,” says Ph.D. student David Bailey, who is working under the direction of Lawrence and entomology associate professor David Held.

And the answers were Yes, Yes and Yes.

The earthworm-nematode project was spawned by sheer curiosity on the part of Bailey, who earned his master’s in entomology from Auburn in December 2012 under Held’s guidance with research on mole crickets’ tunneling behaviors.

“I was in a cotton field one day and noticed there were a lot of earthworm castings on the surface, and I started wondering whether there were any nematodes in the casts,” says Bailey. “This whole side project has sprung from there.”

For the study, Bailey collected earthworms and earthworm castings — excrement the worms deposit on the surface — from nematode-infested cotton fields located at Auburn University’s E.V. Smith Research Center in east-central Alabama and the Tennessee Valley Research and Extension Center in Belle Mina.