Nematodes are both natural soil residents that contribute to healthy, productive soils and parasitic, free-living organisms that feed on living material. About 25 to 30 species of nematodes that feed on corn have been identified in Midwestern fields. While nematodes are recognized as a major soybean pest, their effect on corn is less well known. A study by university agronomists found nematodes in 80% of the corn fields sampled in Illinois had plant-feeding nematodes. Similar results have been found in other corn growing states. In addition to sandy soils, continuous corn fields and no-till fields are the likeliest areas for nematode problems.
When scouting a field, look for damage in circular patches within a field. The most obvious sign of nematode damage is wilted leaves. Plants that are stunted by nematodes might appear to be suffering from a nutrient deficiency because the damaged roots can’t take up nutrients. When corn is in the rapid growth stage, damage can increase dramatically over a few days.Nematodes in field corn reduce feeder roots and produce root stunting. When looking for symptoms of root damage, the roots should not be pulled but rather should be carefully dug with a shovel. Pulling roots out of the soil will strip away the fine root hairs. The most common type of damage to corn is root rotting caused by fungi entering the root hairs through infection ports made by nematodes.Compare roots from a possible nematode hot spot to the roots of normal plants. Damaged roots may have a stopped-off or club-shaped appearance. The tips may turn brown and stop growing. There may also be a noticeable lack of root hairs.
Having soil in suspected areas analyzed for nematode counts will establish baseline levels that can help you decide whether a nematicide treatment will pay in the future. All the nematodes that damage corn also feed on weeds and other crops. The most appropriate control measure depends on which nematodes are causing damage. Maintaining good plant health helps plants resist nematodes. Rotating crops and controlling weeds may help reduce the population of some nematode species. Selecting hybrids with known genetic nematode resistance may be an effective investment and seed treatment nematicides should be considered as part of an integrated approach.