Nematodes are a problem that's more widespread than you might think. Every type of crop - including corn - has at least one type of parasitic nematode species. While a management practice like crop rotation can help, because certain species can feed on multiple crops, it alone doesn't provide adequate protection.
Stealing Yields and Getting Away With It
Nematodes are responsible for an estimated 10.2% yield loss in corn.* Most corn growers aren't aware that their impact is so significant. The numbers aren't any better in soybeans and cotton: 10.6% and 10.7% yield loss, respectively.* In all three crops, they don't just feed on roots. They create hidden yield loss in several ways.
Nematodes can burrow into roots, feeding on the water and nutrients inside (depriving the plant of what it needs), and damaging the root cells as they move around. Plus, when they pierce the root, they leave the plant susceptible to other yield-robbing threats like fungi, diseases and viruses.
Scott Spal, a research scientist who has spent nearly a decade studying nematodes, explains the different ways nematodes can impact yield: "If you have nematodes feeding on your plants, you're creating an environment in which all other problems are going to be exacerbated. Fungal and bacterial pathogens have an entry into the plant. You're going to reduce the ability for that plant to move water. Nematodes are robbing yield directly, but they're also giving access to other problems in the field."
One microscopic nematode might not seem like it can do a lot of damage, but a single female can lay hundreds of eggs in just a month, exponentially increasing populations very quickly.
Limited Awareness of Risk While cotton growers tend to be more aware of nematodes as a threat to their yields, only some soybean growers (25%), and even fewer corn growers (8%) believe that nematodes impacted their yields in 2016.** Yet a 2016 study found that 80% of corn acres sampled in the US have nematode pressure.*** Even among growers who are aware of nematodes as a potential threat, the damage they can do is being vastly underestimated.
Recent research has put soybean cyst nematodes (SCN) in the spotlight. However, because SCN eggs can be seen with the naked eye, many people believe that nematodes themselves can be seen. This is a misconception - nematodes are microscopic. In fact, nematode damage can also be invisible: often, no above-ground symptoms will appear. And if they do appear, there's no way to control nematodes mid-season.
Nematodes in Every Soil Type
Beyond SCN, there are hundreds of other types of nematodes, living in every soil type, in every region of the United States.
"The lesion nematode, a major nematode species in corn in the U.S., prefers a higher clay content. However, there's at least one nematode that fits in every soil type," explains Dr. Davie Wilson, Technology Development Manager at Monsanto. "For instance, needle nematodes and root-knot nematodes prefer a siltier, sandier, more coarse-textured soil type."
Dr. Wilson continues, "Some species are more prevalent in the Southern growing regions because it's a little bit warmer there during the calendar year. But SCN is ubiquitous. Minnesota and South Dakota growers can have a high level of SCN - or even lesion nematodes, which can feed on both corn and soybeans. And there are corn farmers in North Dakota who have a lot of needle nematodes."