Ten Things You Should Know about Corn Nematodes
Terry L. Niblack
Department of Crop Sciences
Department of Crop Sciences
- Many agrichemical companies are developing products for corn nematode management. Don’t fall for hype – be sure to check out the claims before investing in these products. Also, be sure that you know what the corn nematode situation is on your farm (see item #10).
- Most people think “corn nematodes” are just one type of nematode, but there are at least 10 species that are very common in Illinois. Most of the nematodes that attack corn are native species - that is, they also parasitize grasses and other native prairie plants. Because they’re very well adapted to life in Illinois, you can’t get rid of them; you can only encourage or discourage them.
Nematodes are the most frequently overlooked cause of corn disease. They feed on corn roots and cause
symptoms that could be blamed on many different kinds of stress (see photos).
- Most insecticides applied to the soil have little or no effect on nematode damage. If it’s not labeled as a nematicide, it won’t control nematodes.
- All soil types may be home to one or more species of corn-pathogenic nematodes. Nematodes are not limited to sandy soils, as many people think. The damage caused by nematodes is more obvious and dramatic in sandier soils, but damage occurs in heavy soils as well.
- You can sample soil any time for corn nematodes. Timing of sampling depends on many factors, and there isn’t really a “best” time – sample when you need to know. In general, nematode populations are highest in the fall, around harvest. Numbers of nematodes in soil in the fall are often good predictors of the numbers that will be there in the spring. Summer sampling is difficult because many nematodes will move downward in the soil, with the moisture; however, it can be done. Spring sampling is the easiest, at about a month after planting. Sample in the root zone.
- Most nematodes that attack corn will not attack soybean – or if they do, it’s at a lower level. Likewise, soybean cyst nematode and other soybean nematodes do not thrive on corn.
- Continuous corn production will increase the populations of corn-parasitic nematodes. Some important corn nematodes have long life cycles (several months), and growing corn-on-corn gives these an opportunity to build up that they would not otherwise have. For the same reason, it’s important to control grassy weeds in soybeans, because these are often hosts for corn nematodes.
- Soil samples for nematode analysis should be treated GENTLY. Some common and highly pathogenic species are extremely sensitive to disturbance. Soil samples should be protected from heat and “bumping,” and placed in an insulated box for transport to a lab.
- Management of corn-parasitic nematodes depends on proper diagnosis! Submit your corn samples to the Plant Clinic (see http://plantclinic.cropsci.illinois.edu/), the Nematology Lab (AW101 Turner Hall, University of Illinois, Urbana, IL 61801), or a reliable private lab.