Subscribe and stay up-to-date with the latest news and great offers from DEKALB, Asgrow and Deltapine.
Don't miss out on the latest agronomic news.
Local agronomic alerts.Delivered straight to your inbox.
Nematodes feeding on corn and soybean roots cells reduce the ability of the plant to take up water and nutrients. Yield losses, caused by nematodes, can easily go undetected, and may be attributed to herbicide carryover, sandy soils, soil compaction, and other problems. Nematode sampling, identification, and treatment may protect yield potential. Farmers may want to sample low performing areas of fields to determine whether or not nematodes are limiting yield potential.
Symptoms. Nematode feeding symptoms are most noticeable when environmental conditions cause plant stress. Common aboveground symptoms include wilting, yellowing, and stunting of growth. However, nematodes may cause yield loss without exhibiting aboveground symptoms. Common below-ground symptoms include swollen roots, lack of fine roots, minimal root branching, and necrotic lesions (Figure 1).Below-ground symptoms can differ depending on which nematode species is causing injury. For instance, different corn root symptoms may result from feeding by lesion, sting, or stubby-root nematodes. In many cases, nematode feeding occurs at the growth point of the root, and the resulting damage is apparent as stunted roots. Severe nematode damage will result in “stubby roots�? with many short, swollen roots.
Nematode damage is rarely uniform within a field, and damage is typically more visible in areas with sandier soils. A common misconception is that nematodes are worse in sandy soils. Nematodes infest many types of soil.Drought-prone, sandy soils may allow aboveground nematode damage symptoms to become more visible.
Testing for Nematodes. To confirm the presence of nematodes in corn, soil and root samples must be taken and submitted to a nematode testing facility. Generally, only soil samples are required to confirm the presence of soybean cyst nematode (SCN). Treatment recommendations can be made after test results confirm nematode species that are present and their approximate population density. Refer to university recommendations for treatment thresholds. Nematode distribution can be very irregular within a field; therefore, it is important to collect several composite samples to provide an accurate population estimate.
When collecting and shipping samples, handle with care to avoid killing nematodes before they reach the lab. Follow lab instructions for collecting, handling, and shipping all nematode samples.
Management. Because there are many nematode species, identification is essential for determining the appropriate control option (Table 1). Management practices that reduce crop stress may help the crop overcome nematode feeding.
Table 1. Important Nematode Species in Corn and Soybean.
The following agronomic practices may help growers manage potential nematode infestations.
1 Niblack, T. 2010. Time to plan for corn nematode sampling. The Bulletin. University of Illinois. No. 4 article 6. http://bulletin.ipm.illinois.edu/print.php?id=1293.
2 Tylka, G. 2007. Nematodes in corn production: a growing problem? Integrated Crop Management. IC-498. Iowa State University Extension. http://www.ipm.iastate.edu/ipm/icm/2007/2-12/nematodes.html.
Web sources verified 04/11/17.170411203857