Know Your Nematode Threat Level | Soil for Tomorrow | Corteva Agriscience
 11/4/2021

Know Your Nematode Threat Level

Soil sampling probe filled with soil

Have you tested your soil for nematodes this fall? No? It’s not too late to discover what plant-parasitic pests are lurking underground and preparing to feast on your crop’s root system.

Proper timing is critical to successfully evaluating the nematode yield threat present in each field.  

To increase the efficacy of soil sampling, University of Arkansas nematologist Travis Faske recommends pulling soil cores as soon as possible, and ideally within six weeks of fall harvest. If that is not possible, sampling into early December in warmer climates should still yield serviceable results.

Suggested sampling depths range from at least six to eight inches, depending on the crop’s root zone. Faske recommends using a standard soil probe, routinely used to collect soil samples for fertility. Soil samples should also be taken from multiple areas of each field to adequately determine nematode pressure.

“You would not apply fertilizer based on one field sample, so don’t manage a pest based on a single sample either,” Faske says.

Faske cautions against sampling when soils have standing water present, because the accuracy of nematode densities in the sample will be compromised. He also recommends shipping soil specimens as soon as possible after sampling to improve testing results.

Nematode populations are not readily apparent to the naked eye, but the feeding damage they cause to crop roots is more easily identified.

Often misdiagnosed, or wrongly attributed to lack of moisture or plant stress, nematode damage symptoms include uneven growth patterns with stunted plants, yellowing of plant leaves, reduced fruit set and a decrease in both yield quantity and quality (size). Water and nutrient uptake is also decreased by nematode root feeding, and nematode-inflicted damage can allow fungal disease to more easily infect plants.

If left uncontrolled, yield loss from nematode feeding can be substantial. Yet scouting for nematodes is often an afterthought, at best.

There are steps you can take to limit your nematode liability.

  1. Test your fields regularly to know your population numbers.
  2. Take soil samples at the same time each year, preferably in the fall.
  3. Send samples to the same lab each time for processing consistency.
  4. Rotate with resistant crop varieties, if possible.
  5. Rotate to non-host crops, if possible.
  6. Consider using a nematode-protected seed treatment or in-furrow treatment at planting, if applicable.
  7. Minimize weeds in fields as they too can harbor these pests.