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Post-harvest is a good time to sample fields for fertility, soybean cyst nematode (SCN), and even some nematodes that attack corn. While it is possible to detect SCN cysts on soybean roots with a hand lens, soil sampling is the only way to detect nematode species that feed on corn. When above-ground symptoms, like yellowing or stunting, are observed, yield potential may have already been reduced.1 Early detection and proactive management are necessary to prevent significant yield reduction and keep population densities low.
Soybean Cyst Nematode. Crop rotation is a critical element of a management plan because high soil SCN egg levels may require one or more years of non-host crops to reduce egg numbers low enough to plant susceptible crops. Soybean products with SCN resistance can inhibit SCN reproduction, therefore reducing egg levels in the soil. Soybean products vary in their source of resistance and the degree of resistance in each product. Growers should be aware that SCN populations can adapt to previously resistant soybean products. Continued use of one resistant soybean may result in a change in the nematode population and can lead to that form of resistance no longer being useful for that field. This can be avoided by not planting a resistant product two or more consecutive years in the same field. Nematicide seed treatments can help provide early season protection against SCN.
Corn Nematodes. Sampling for corn nematodes should generally be done early to mid-season, when nematodes levels are greater and damage symptoms, such as stunting or yellowing, are observed. Population densities of many nematode species that feed on corn drastically decline after the crop matures and is harvested, so low numbers from fall sampling may not be indicative of damaging numbers earlier in the season. However, there are a few corn nematode species where fall sampling is acceptable or even preferred. These include, root-lesion, lance, needle, and sting nematodes.2
Root-lesion and lance nematodes. Root-lesion and lance nematodes are endoparasites, meaning they enter the corn roots to feed and reproduce. Sampling may be done early or mid-season for these species, but fall sampling is also acceptable since nematodes accumulate in the root tissue throughout the growing season. Samples must be taken from both the soil and root fragments.
Sting and needle nematodes. These nematodes are found in soils with 70 percent or greater sand content. During the growing season sting and needle nematodes migrate deep into the soil and may be missed by soil samples. Sampling for these nematodes may be done in the spring or fall in fields where damage is suspected.
Nematode Sampling Guidelines. Fall sampling can be done before or after harvest before any tillage is conducted. Samples should be collected from fields that displayed obvious symptoms of possible nematode damage, such as yellowing or stunting. The most important areas to sample include: field entries, low spots, flood-prone areas, consistently low yielding spots, shelter belts and fencelines, late season yellow spots, and high pH soils. A general procedure for taking nematode soil samples:
Contact your local testing facility for specific sampling recommendations and interpreting results.
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, corn and cotton crops. Some of the nematodes controlled include soybean cyst, root knot, lesion, lance, reniform, sting, and needle.
With a novel mode of action, low water solubility, and synthetic nematicide (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 DEKALB®and Asgrow® brand seed purchasers. Please contact your DEKALB and Asgrow brand seed providers for additional information.