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Through the years, parasitic nematodes have been the cause for yield losses of greater than 10% in each of the following three United States crops: corn, soybean, and cotton.1 Microscopic nematodes pierce plant roots, which can help facilitate plant bacterial, fungal, and viral infections.
Figure 1. Soybean cyst nematodes on soybean roots.
Nematode damage is frequently underestimated and misattributed to stresses associated with drought, fertility, chemical injury, and disease. Symptoms may not be visible or appear as wilting, yellowing, or stunting. The presence of nematode species can vary based on environmental conditions, soil type, and the presence or absence of actively growing plants that support their life cycle. Yield loss attributed to nematodes has been estimated at 10.2% for corn, 10.6% in soybean, and 10.7% in cotton.1
Nematodes are able to enter fields through soil movement including the wind, shovels, boots, farm machinery, and animals. It has been estimated through sampling that over 80% of U.S. corn acres are infested with at least one species of nematode.2
Testing for Nematodes. Typically, fall is the best time to sample fields for soybean cyst nematode (SCN) presence because the results will be available to use when determining seed product selection for the next growing season. It is recommended to limit the size of the sampled area to 10 to 20 acres when collecting soil samples for SCN analysis.3 Use a soil probe and take about 20 cores throughout the sampling area. Thoroughly mix the soil cores into a composite sample and submit about a pint of soil to a nematode sampling lab. 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 samples, handle with care to avoid killing nematodes and promptly ship to a lab. Follow lab instructions for collecting, handling, and shipping all nematode samples.
To confirm the presence of nematodes in corn, soil and root samples must be taken during the early to mid growing season, and submitted to a nematode testing facility. Generally, only soil samples are required to confirm the presence of SCN.
There are commercial and university nematode testing laboratories. University of Missouri and Kansas State University provide screening for SCN and corn nematodes at their respective diagnostic labs. Further information on collecting and submitting samples is available at:
Treatment recommendations can be made after test results the confirm nematode species that are present and their approximate population density. Refer to university recommendations for treatment thresholds.
Crop protection has primarily been limited to crop rotation, use of resistant soybean products, and available nematicides. However, the EPA recently approved the use of NemaStrike™ Technology, a seed treatment technology that provides broad-spectrum nematode control for soybean (Figure 1), corn (Figure 2), and cotton crops. Some of the nematodes controlled include soybean cyst, root knot, lesion, lance, reniform, sting, and needle.
Figure 2. Corn nematode feeding damage. Photo courtesy of Jason Bond, Southern Illinois University.
With a novel mode of action, low water solubility, and new chemistry (Tioxazafen), NemaStrike™ Technology defends crops from the start and stays in the root zone as plants grow for up to 75 days. In numerous field trials over 3 years, the technology has helped to protect the average yields of corn by 7 bu/acre (100 trials), soybean by 3 bu/acre (113 trials), and cotton by 80 lbs lint/acre (51 trials).3 Performance results will vary based on nematode pressure.
Acceleron® Seed Applied Solutions with NemaStrike™ Technology will be offered to Asgrow® and DEKALB® brand seed purchasers. Please contact your Asgrow and DEKALB brand seed providers for additional information.