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 1/24/2024

Soybean Cyst Nematode Populations Across Northern Iowa - 2023

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Soybean Cyst Nematode Populations Across Northern Iowa - 2023

Agronomy Research Update
Written by Nate LeVan, Bill Long, Cale Gent, Nick Hanson, Nate Pech, Troy Deutmeyer, Alex Woodall, Jake Bates, and Chris Phipps; Pioneer Agronomy Sciences.

Key Points

  • More than 93% of fields sampled had soybean cyst nematode (SCN) population levels capable of causing some level of crop damage (10% or greater yield loss potential).
  • SCN egg counts were 61% lower on average in areas of the sampling locations planted to varieties with Peking SCN resistance compared to areas planted with PI88788 varieties.
  • Soybean growers can reduce the risk of SCN damage by planting resistant varieties, rotating between PI 88788 and Peking resistance sources, and using a nematode protectant seed treatment such as ILEVO® HL.

Related Articles

Objective and Study Description

  • Soybean cyst nematode (SCN) samples were collected from 61 soybean fields in northern Iowa to determine SCN population levels and potential for soybean yield loss (Figure 1).
  • Sample locations included varieties with PI88788 and Peking SCN resistance sources planted in the same field. SCN samples were collected from both.
  • Fields were sampled at the end of the growing season following harvest.
  • Sample cores were taken to a depth of approximately 6 inches.  Subsamples from across the PI88788 or Peking variety areas were blended into composite soil samples and submitted to Ever-Green Nematode Testing Labs for analysis.

Results

  • SCN infestations were found throughout the study area, with more than 93% of fields sampled having some level of SCN infestation that could lead to yield losses greater than or equal to 10% (Table 1).
  • 54% of fields sampled had SCN population levels capable of causing moderately high to severe crop damage (>20% yield loss) (Table 1).
  • SCN egg counts were 61% lower on average in areas of the sampling locations planted to varieties with Peking SCN resistance compared to areas planted with PI88788 varieties (Figure 2).
  • 48 of the 61 sample fields (79%) had lower SCN egg counts in the areas planted to varieties with Peking SCN resistance compared to areas planted with PI88788 varieties (Figure 2).

    Table 1. SCH population classifications, population levels of 2023 study locations, and potential soybean yield loss.

    SCN Population
    (eggs/100 cc of soil)    		 Percent of Sample
    Locations in 2023
    		 Potential Yield
    Loss with no
    Management*
    Zero 1.6 ---
    Low (<500 eggs) 4.9 Unlikely
    Moderate (500-2000) 23.9 ~10%
    Mod-High (2000-5000) 32.8 ~20%
    High (5000-8000) 13.1 ~50%
    Very High (>8000) 8.2 Very High

    *SCN population classifications and yield loss estimates per analysis reports provided by Ever-Green Nematode Testing Labs. Actual yield loss will depend on multiple factors.

SCN Management

Decreased Efficacy of PI88788 Resistance

  • Beginning in the 1990s, the widespread availability of soybean varieties with PI88788 SCN resistance provided a largely effective management tool for SCN in North America.
  • In recent years however, PI88788 has been losing its effectiveness as a SCN management tool.
  • Levels of reproduction on PI88788 among Iowa SCN populations have increased steadily over the last two decades. These results show that Iowa SCN populations are adapting to PI88788 resistance and the resistance is considerably less effective now compared to when it was introduced in the early 1990s (Tylka, 2022).

Management Recommendations

  • The SCN Coalition provides the following recommendations for developing a plan to manage SCN (www.thescncoalition.com):
    • Test your fields to know your numbers
    • Rotate resistant varieties
    • Rotate to non-host crops
    • Consider using a nematode protectant seed treatment

Rotate Resistant Varieties

  • If your SCN populations are found to be increasing, select varieties with sources of resistance other than PI88788.
  • The most common source of resistance other than PI88788 is PI548402 or “Peking” resistance.

Rotate to Non-Host Crops

  • Rotation to a non-host crop to reduce SCN pressure. 
  • Corn, alfalfa and small grains are the most common non-crop choices for reducing SCN numbers. 
  • Since SCN persists in the soil for many years, it cannot be totally eradicated by rotation.

Seed Treatments

  • Several nematicide seed treatments with activity against SCN are currently available and can provide added protection when used with a SCN-resistant soybean variety.
  • Nematicide seed treatments are intended to supplement current SCN management strategies, not replace them. Seed treatments should therefore be used in coordination with SCN-resistant varieties and rotation to non-host crops.
  • The LumiGEN™ system offering includes ILEVO® HL fungicide/nematicide seed treatment, which has activity against SCN.

Reference

Tylka, G.L. 2022, High Reproduction of SCN Populations on PI 88788 Resistance is Frightening, Iowa State University, ICM online newsletter.

Figure 1. SCN sampling locations and population levels across northern Iowa in 2023.

SCN sampling locations and population levels across northern Iowa in 2023.

Click here or on the image above for a larger view.

 

Figure 2. SCN egg counts from areas planted to Peking or PI88788 soybean varieties at 61 northern Iowa sampling locations in 2023.

SCN egg counts from areas planted to Peking or PI88788 soybean varieties at 61 northern Iowa sampling locations in 2023.

Click here or on the image above for a larger view.


LumiGEN seed treatments  ILEVO HL seed treatment

Components of LumiGEN® seed treatments for soybeans are applied at a Corteva Agriscience production facility or by an independent sales representative of Corteva Agriscience or its affiliates. Not all sales representatives offer treatment services, and costs and other charges may vary. See your sales representative for details. Seed applied technologies exclusive to Corteva Agriscience and its affiliates. Pioneer® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents. ILEVO® HL is a registered trademarks of BASF.

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. 2023 data are based on average of all comparisons made in 61 locations through November 1, 2023. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. Product responses are variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.