Soybean Cyst Nematode Populations Across the Midwest in 2021

Written by Mary Gumz, Ph.D., Pioneer Agronomy Manager

Study Description

• 439 soybean fields in Iowa, Minnesota, Missouri, Indiana, Illinois, Michigan, Wisconsin, Kansas, and Ohio were sampled to determine soybean cyst nematode (SCN) pressure in 2021.
• Sampling was concentrated in a total of 55 sampling areas (shown in Figure 1), with samples collected from multiple soybean fields within each sampling area.
• Soybean fields were sampled during the growing season at a depth of approximately 6 inches. Subsamples from across the field were blended into a composite soil sample and submitted to a nematode testing laboratory.
• Samples were analyzed using a sugar-floatation method and sieved through a 120-mesh sieve for adult cysts and a 500- mesh sieve for cyst larva not yet in the root system.

Figure 1. Sampling areas for SCN populations in 2021. Multiple fields were sampled in the vicinity of each point shown on the map. Click here or on the image above for a larger view,

Strips of SCN-resistant and non-resistant soybean varieties in a SCN-infested field showing damage to the non-resistant varieties.

• Potential for SCN damage describes the likely damage to a SCN-susceptible soybean variety with no SCN management taken and is based primarily on the number of eggs per 100 cc of soil. Some samples with very high adult or larva counts may be rated as a higher potential damage class than they would have been if based on egg counts alone.

Results

• SCN infestations were found throughout the study area, with over 80% of fields sampled having some level of SCN infestation (Figure 2).

Figure 2. Soybean cyst nematode pressure levels across all 439 soybean fields sampled in 2021.

Table 1. Number of sampling areas and total fields sampled for each state, and sampling results showing the percent of SCN samples in each of six potential crop damage categories.

• 27% of fields sampled had SCN population levels capable of causing heavy to severe crop damage (Figure 2).
• All areas sampled in this study were within the known geographic range of SCN in the U.S. (Tylka and Marett, 2021).
  • Iowa, Minnesota, Missouri, Indiana, and Illinois were the most extensively sampled states in the study. The percentage of fields with heavy to severe SCN pressure in these states ranged from 16 to 38% (Table 1).
  • Wisconsin, Kansas, and Ohio had no fields with more than a slight potential for SCN damage but had a very small number of fields sampled. Conversely, Michigan had a high percent of fields with heavy to severe SCN pressure, but also had a very limited number of samples (Table 1).

SCN on soybean roots.

SCN Management Recommendations

• Test soybean fields for SCN.
• If no infestation is found, use good management practices and rotate a combination of resistant or susceptible varieties in the field.
• If SCN is found:
  • Plant SCN resistant soybeans. Rotate between varieties with PI 88788 resistance and Peking source resistance.
  • Consider using a nematode protectant seed treatment such as ILEVO^® seed treatment. The LumiGEN^® seed treatment offering includes ILEVO^® seed treatment, which has activity against SCN. A Pioneer study including 193 on-farm trial locations found an average yield response of 4.9 bu/acre in high SCN fields when ILEVO fungicide/nematicide seed treatment was added to the standard fungicide and insecticide seed treatment package (O’Bryan and Burnison, 2016)¹
  • Rotate to non-host crops such as corn.
  • Control alternate weed hosts such as henbit, purple deadnettle, field pennycress, shepherd’s purse, small- flowered bittercress and common chickweed.

References

• O’Bryan, K., and M. Burnison. 2016. Performance of Soybean Seed Treatments Against SDS and SCN in On-Farm Trials. Pioneer Agronomy Research Update. Vol. 6, No. 7.
• Tylka, G.L., and C.C. Marett. 2021. Known distribution of the soybean cyst nematode, Heterodera glycines, in the United States and Canada in 2020. Plant Health Progress. 22:72-74.