What is Soybean Cyst Nematode (SCN)?

Soybean Cyst Nematode (SCN) is the most damaging soybean pathogen in North America. Under severe SCN pressure, with no cyst protection, farmers can experience up to 50% yield loss, and even fields with no visual symptoms can see up to a 10% yield loss.¹ 

Where is Soybean Cyst Nematode Been Reported?

SCN was first identified in Canada in a field near Chatham, Ontario in 1988. Since than there has been a steady expansion of SCN infected acres in Canada. Most recently between 2017 and 2020 the map below shows in blue the new SCN-infested counties compromising a majority of acres in Eastern Canada and new presence in southern Manitoba.
 

Known Distribution of the Soybean Cyst Nematode, Heterodera glycines, in the United States and Canada in 2020. Gregory L. Tylka  and  Christopher C. Marett -  https://apsjournals.apsnet.org/doi/10.1094/PHP-10-20-0094-BR

Protecting Your Yield

While using seed treatment products like Draco™ and Saltro® can provide a second mode of action to deliver SCN suppression for your soybeans, genetic resistance to SCN is the most reliable measure against this pathogen, as it provides season-long protection.

For more than 20 years, greater than 95% of all SCN-resistant soybean varieties have included resistance from the PI 88788 breeding line (Soybean SCN Coalition). And now we’re experiencing a race shift. With the continued use of PI 88788 as the main source of genetic SCN resistance, we are seeing increased cyst reproduction rates across US and Eastern Canada on PI 88788. What this means is that PI 88788 is not providing >90% reduction in cyst, potentially resulting in higher yield losses.²

That doesn’t mean that PI 88788 is not a great tool to manage SCN. PI 88788 is still providing some control, but other sources should be considered such as Peking to maximize yield potential.


 
The Power of Peking

On soils where PI 88788 is no longer as effective in managing SCN populations, varieties with the Peking source of SCN resistance offer a great tool to minimize yield loss. Pictured is an example of what can happen with significant race shifts and the different SCN resistant genetic responses. The two Peking varieties show minimal impact, but the PI 88788 varieties exhibit severe stunting. Additionally, even in the absence of visual symptoms yield loss may still be occurring.¹
 

Yield Impact: In 2018 this location was taken to yield (picture not shown). Peking varieties yielding 70+ bushels per acre while PI 88788 varieties yielded 40-50 bushels per acre. (Syngenta R&D 2018). If price/bu=$15, using a PI 88788 variety could potentially result in revenue loss of $240-495/acre.

Peking varieties should be considered another tool in growers’ SCN management plan or toolbox. Regardless of whether you think you have race shifts or not, use of a Peking variety is a great strategy to manage yield loss.

Rotation of SCN sources PI 88788 and Peking (PI 548402) is strongly encouraged to limit SCN reproduction and economic injury levels. Additionally, limiting SCN reproduction will reduce root damage caused by nematodes that can open up the door for late-season diseases like Sudden Death Syndrome (SDS) and Brown Stem Rot which can further reduce yield.

SCN is widespread across much of Ontario and even Quebec. Use of new sources of resistance including Peking (PI 548402) is strongly recommended to combat race shift already occurring and limit future race shift.

The NK soybean portfolio offers several SCN-resistant varieties with the Peking breeding line, including:

• S14-W6E3
• S18-F1E3S
• S26-E3
• S29-R5X

What is SCN Field Tolerance?
 
In addition to our genetic resistance options (Genotype - PI88788 or Peking – PI 548402), Syngenta goes one step further with and both an internal and external SCN assessment with a Physical Greenhouse Screen to assess the actual reproductive capacity of SCN cysts on the soybean variety. This helps use understand the level of natural field tolerance a variety will have with or without the addition of genetic resistance. The lower the filed tolerance score the better the natural ability of the variety to tolerate a SCN infection.

Summary

Soybean cyst nematode is a common soil borne disease that can result in significant yield loss.  In addition, the root damage caused by SCN can lead to other secondary diseases like Sudden Death Syndrome (SDS) and Brown Stem Rot (BSR) to further reduce the yield potential in the field.

While some seed treatments can provide some SCN protection, the best solution is to use the variety tolerance with natural field tolerance and/or genetic resistance. Due to race shifts with SCN populations, the reliance on the long-standing genetic resistance with PI 88788 may not be sufficient. Watching for performance in the field and better yet, the proactive use of soybean varieties with the new Peking source of resistance we will continue to keep SCN managed to optimize soybean performance in the field.

Speak to your local NK^® Seeds Agronomist for more information, or join the conversation online – connect with us at @NKSeedsCanada on Twitter and Facebook.

These are general considerations. Always consider the specific situation on your field and exercise good agronomic practices.
Always read and follow label directions. NK^® is a trademark of a Syngenta Group Company. © 2023 Syngenta.

¹ Wang et al. Plant Disease 93:623-6280
² SCN Coalition