Nematodes: We’re Back

After several decades of reprieve for growers, an indigenous and damaging pest is again creeping through the Corn Belt. Nematodes are making a comeback.

While traditional production practices hindered nematode populations in corn, cultural changes in today’s production have caused their recent increase. For example, more than 80 percent of Illinois soybean fields are infested with soybean cyst nematode (SCN), according to Terry Niblack, University of Illinois Extension nematologist (see “To Every SCN: Turn, Turn, Turn”).

There are three major changes that have contributed to this growth — and that will continue to encourage growth in the future.

  • First is an increase in no-till and reduced-till farming methods. Because most nematode species are sensitive to tillage, no-till and minimum-till production practices can create an environment where certain nematode species are able to flourish year after year.
  • Second is a change in rootworm management technology. Pyrethroid insecticide chemistries and corn rootworm (CRW)-traited corn don’t suppress corn nematodes as did the older carbamate and organophosphate insecticide formulations.
  • Third is an increase in corn-on-corn planting, which allows nematode populations to prosper. A rotation with alfalfa or another non-host crop can help hinder life cycles.

Damage caused by corn nematodes is difficult to identify because symptoms can easily be attributed to other causes such as herbicide injury, diseases, micronutrient deficiencies or the result of harsh environmental conditions such as drought. Some species of nematodes may not cause economic injury on their own, but can interact with other problems, such as fungal pathogens and insects, to intensify corn yield loss. Often there are no visual symptoms, but corn yield is impacted. The only way to accurately identify nematode populations is through collection and analysis of soil and root samples.

To measure the prevalence of nematodes in corn fields, Syngenta Seed Care launched a corn nematode mapping project in 2007. In the first comprehensive study of its kind in the Midwest, Syngenta Seed Care sampled three fields in each county that grows at least 25,000 acres of corn in the Midwest Corn Belt.

The fields sampled were randomly selected — the only criterion was the fields had to be at least 10 miles apart. There was no pre-selection for soil type or tillage, and the samples were taken from corn-on-corn and corn-on-soybean rotation fields.

Samples were processed by five university labs and one private lab. The results mapped intensity by species and overall nematode populations for every county included in the study. While species and populations varied, nematodes were found in every county included in the survey.

Syngenta Seed Care recognizes the threat that growers face with corn nematodes and is working to bring to market a corn seed treatment nematicide to help manage the threat of yield loss caused by corn nematodes. For more information, please contact your Syngenta Seed Care sales representative.

(Sources: Plant Management Network News/Syngenta Crop Protection)

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