Reaching Nematodes Where They Live

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Potato field

How does a nematicide’s ability to move through the soil influence its effectiveness against plant-parasitic nematodes?

Achieving optimum soil movement is critical to a nematicide effectiveness. Successfully targeting the root zone with ideal soil distribution requires a nematicide with superior water solubility.

“The most efficacious nematicides exhibit the precise mobility characteristics required to get the crop protection product where it needs to be without traveling farther than is needed,” says Marta Garcia, Corteva Agriscience global program leader for insecticides and nematicides.

Soil-applied nematicides must move through the soil well enough to target yield-robbing nematodes within the root zone. Too little soil distribution and the nematicide’s effects are short-lived and become unable to protect roots as they grow. Too much soil movement and the active ingredient diminishes and is no longer effective.

“Some nematicide products have less soil movement, which can be a strong negative,” Garcia says. “Nematodes don’t just exist within a few inches in the soil.”

Proper soil distribution of nematicides provides long-lasting residual control of plant-parasitic nematodes. Residual activity length also depends on application rates, available moisture, temperature, microbial activity and soil type. Other chemical characteristics, such as molecule size, also play a role in soil distribution and efficacy.

Nematicide treatment decisions should be based on soil test results and field history. Soil sampling alone is only one data point in a grower’s decision-making process.

For most high-value crop producers, it is highly likely that nematodes are threatening their yield and marketability potential.

In fact, a 2018 University of Georgia survey found 94% of the state’s crop fields were infested with 10 types of nematodes documented across the state. The same study found 66.8% of vegetable fields in Georgia are infested with root-knot nematode.

There are differences among plant-parasitic nematodes regarding the damage they can cause to crops, and their sensitivity to nematicides.

Root-knot nematodes (Meloidogyne spp.) are the most widely-distributed and destructive nematodes. Among root-knot nematodes, the Southern root-knot nematode (M. incognita) is arguably the most economically damaging nematode species for U.S. agricultural producers.

Like many other nematodes in the Meloidogyne genus, the guava nematode (M. enterolobii) has a wide host range and is a significant ongoing risk to global agriculture. Differences that set this root-knot nematode species apart from other Meloidogyne species are a very high reproduction rate, and increased severe crop injury and virulence against the primary root-knot resistance genes currently deployed in crops. Because of this, it is a quarantine species in the U.S. states where it occurs.

Another nematode of concern for growers in the United States is the reniform nematode (Rotylenchus spp.), which can cause significant damage to a variety of crops, particularly cotton. Other plant-parasitic nematodes include dagger, spiral, stubby-root and root-lesion nematodes.