Is Soybean Cyst Nematode (SCN) getting worse?

SCN can still reproduce on roots, even with PI 88788, the most commonly used source of resistance in soybean varieties to combat SCN. Based on a recent study by the University of Illinois, our state’s most common HG type is 2.5.7. This tells us that these populations can reproduce on PI 88788, PI 209332, and PI 548316. In fact, 100 percent of the populations in that study could reproduce on PI 88788, the primary source of resistance to SCN, highlighting that we are losing an essential management tool.

So, how do we currently manage SCN?

A very important management strategy against SCN is a rotation with a non-host crop such as corn to help to deplete SCN populations. If PI 88788 is failing, farmers may be encouraged to seek a variety that consists of Peking resistance.  Seed treatments are also a management tool that only affects the first wave of juveniles that attack the roots. We currently need a multifaceted approach to combat SCN but also want to look at other management tools such as cover crops and methods to pinpoint the pest in fields.

Is Peking the answer to our SCN problems?

Dr. Jason Bond, professor in crop, soil and environmental management at Southern Illinois University, explains, “Peking was discovered in 1957 and used in the south in the 70s and 80s. Breeders struggled with yield drag in this part of the country, and feared competitors would place their Peking varieties in fields with low levels of SCN and perform poorly in yield trials. I believe breeders removed the yield drag and Peking varieties are slowly increasing in availability, however mostly in the 3.3 MG or earlier.”

Normally, southern Illinois counties require soybean varieties higher than a 3.3 MG, but according to Dr. Bond, “farms that are located in White and Gallatin counties plant very early MG’s (1 and 2) under center pivots, so this allows them to get access to soybean maturities with Peking resistance.”

What are some SCN research results from soybean varieties with Peking?

Recently, Dr. Bond’s team from Southern Illinois University shared some exciting research results from their SCN and root knot nematode research site, located in Carmi, IL where they test seed treatments and soybean varieties. This year in each plot, they counted SCN females and cysts as well as eggs from 5 plants from a variety that consisted of Peking as well as on with PI 88788. Here are the results:

2024 Carmi Soybean Seed Treatment Site

Results provided by Dr. Jason Bond, Southern Illinois University

As you can see from these results, on average, there were significantly less SCN females and cysts as well as eggs found on Variety A plants with Peking resistance per plot when compared to that of Variety B with PI 88788 resistance.

University nematologist Greg Tylka reminds us that if farmers continually plant Peking, they may also lose their effectiveness over SCN, and it could happen even faster than it did with PI 88788. Therefore, it is very important to pay attention to the source of SCN resistance in your soybean variety each year, use other SCN management strategies such as rotation with corn, and make sure that you rotate Peking resistance with other sources of SCN resistance such as PI 88788.

How can I find out if I have SCN in my field?

Don’t forget that Illinois Soybean Association is funding free SCN testing by emailing freeSCNtesting@illinois.edu to receive a free SCN kit with instructions and a prepaid shipping label for you to ship your soil samples. Allow the U of I Plant Clinic a few weeks to analyze your soil sample for SCN so that they can provide you with an accurate summary of results.