When most corn and soybean farmers hear the word “nematode,” they tend to think only about the nematode species that can cause a nice-looking, healthy crop to turn sickly and ugly, says Greg Tylka, Iowa State University Extension plant pathologist. These “bad,” plant-parasitic nematode species are the ones that feed on crop roots, weakening plants, making them more vulnerable to disease, reducing their nutrient uptake and lowering yields.

Still, not every nematode is a “bad” nematode, notes Tylka. There are many “good” nematode species that are nonparasitic to crops. These nonparasitic, or “good” nematodes, feed on bacteria, fungi and other nematodes, rather than crop roots. These “good,” nonparasitic nematodes can also generate “nematode manure” that can help boost root growth and crop yields.

“Superficially, it may appear that nematodes are so tiny that they couldn't possibly produce enough ‘manure’ to amount to anything significant,” says Tylka. “But there are billions of nematodes in every acre of soil in a corn field, and their waste products can be significant contributors to the soil environment.”