Distribution, Levels, and HG Types of SCN Populations in Missouri

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Agronomy Research Update written by Dr. Melissa G. Mitchum and Amanda Howland, University of Missouri. *Research conducted as a part of the Pioneer Crop Management Research Awards (CMRA) Program.

Background

Soybean cyst nematode (SCN) continues to spread throughout soybean-producing regions of the United States.
Heavy reliance on soybean varieties with SCN resistance from the plant introduction (PI) 88788 is driving changes in the approach to SCN management in Missouri.
Further exacerbating this problem is the increasing prevalence of virulent SCN populations that are able to reproduce on soybean varieties with PI 88788 resistance, thereby reducing its effectiveness.

Objectives

A survey was conducted of grower-submitted soil samples from across Missouri to evaluate the distribution, levels, and HG types of SCN.
Objectives of this study were to:
- Increase awareness among farmers of the presence and level of SCN within their fields.
- Confirm the existence of virulent SCN populations in grower fields and the need for alternative SCN management strategies.

Study Description

Soil samples were solicited from Missouri growers.
293 soil samples were received from different Missouri fields in 2016.
Cysts were extracted from each sample and a SCN egg count was determined for each sample.
HG type tests were conducted for 28 SCN populations representing different regions of Missouri.

Graph showing percentage of soil samples that tested positive for soybean cyst nematode (SCN) - Missouri research trial. — **Figure 1.** Percentage of soil samples that tested positive for SCN.

Results

This study determined that 87% of soil samples tested were positive for SCN (Figure 1).
Samples from 293 fields evaluated showed that 74% of samples had egg counts > 500 eggs/250cc (Figure 2).
All of the SCN populations evaluated for HG type showed reproduction on PI 88788 (HG type 2). Some populations (43%) showed reproduction on both Peking and PI 88788 (HG type 1.2) (Figure 3).
68% of SCN populations had a female index (FI) > 50% on PI 88788 (Table 1).

This is a graph showing number of soil samples at the various SCN egg count threshold values (250cc). — **Figure 2.** Number of soil samples at the various SCN egg count threshold values (250cc).

This is a graph showing HG types of SCN populations (n=28). — **Figure 3**. HG types of SCN populations (n=28).

This is a table showing HG type test results of SCN populations.

*Research conducted by Dr. Melissa G. Mitchum and Amanda Howland, University of Missouri, as a part of the Pioneer Crop Management Research Awards (CMRA) Program. This program provides funds for agronomic and precision farming studies by university and USDA cooperators throughout North America. The awards address crop management information needs of Pioneer agronomists. The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation.

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.