According to the SCN Coalition, soybean cyst nematode is the most damaging soybean pathogen in North America, causing up to $1.5 billion in losses nationwide each year. With seed decision time around the corner, growers need to start thinking about SCN control options for the 2020 season.
Dair McDuffee, seed treatment specialist with Valent U.S.A., offers his insights on 2019 pressure, what that means for 2020 and the questions growers should be asking about seed treatments this fall.
What kind of SCN pressure was identified in the 2019 season? We saw our fair share of challenging conditions this year, especially around getting seed in the ground. While later planting does have the possibility of lowering the number of generations of SCN in the soil, one of the greatest challenges in managing this pest is the fact that SCN can produce a lot of damage without many visible symptoms above ground.
Typically, in drought conditions, SCN damage is more visible aboveground, but for most of the Midwest, drought wasn’t the issue this year. Fields can look exactly the same until you find that one that yields 10% to 20% less than the other at the end of the season. That’s why it’s going to be important to test and monitor your fields.
What could this year’s pressure mean for the 2020 season? SCN field counts for the fields you will plant in 2020 mean everything. Growers need to be on top of the issue now to know where they stand and determine their needs. Different weather patterns can have influence on how many generations occur and symptomology, but you need to treat any field with medium to high fall counts seriously. Once SCN is present in soils, it can’t be eliminated, only managed to limit reproduction.
Who should consider an SCN seed treatment? Anyone who took samples in the fall that showed an actionable threshold should strongly consider a seed treatment for SCN. Threshold levels can vary from area to area, so check your fall test count to see where you stand rather than looking to a national number. If your fields are clear but your neighbors in the county aren’t, it also pays to maintain your low counts by selecting appropriate genetic options and treatment.
What does the SCN control market look like for the 2020 season? There are many more options than in previous years. Choosing your seed-applied nematicide is no longer a binary option. A biological option from Valent U.S.A., Aveo EZ Nematicide, offers activity on multiple nematodes, including SCN, at a low use rate of 0.1 fluid ounce per unit and long-lasting control that colonizes the soil and grows with the plant. Being a biological product means it will colonize the root and grow with the plant throughout the season; whereas with traditional chemistry that’s applied, it does its job and then fades away.
What does recent research share on efficacy of seed treatments for SCN? Research on this pathogen is very difficult because it is hard to get a field with uniform populations. In a series of nine trials across Iowa conducted in 2018 by Iowa State University, Aveo EZ provided a significant increase in yield of 1.8 bushels per acre. Across all our trial work, it is common to see a 2- to 3-bushel-per-acre increase in a field with moderate SCN pressure when Aveo EZ is used.
What are the benefits of using different control options against SCN? Having different control methods can be the key for a few reasons. First, the genetic source of resistance (PI88788) has provided soybean growers with billions of dollars of protection over the last 25 years, but SCN is beginning to reproduce on those soybeans at an alarming rate. Any options we can use to secure this important source of resistance should be added to maintain its efficacy.
Second, not only does having different modes of action protect against resistance forming, different control options can be more active at different times of the year or in different soils. Finding a product that offers a low use rate is beneficial to growers wanting multiple products included in their seed treatment to achieve quality coverage and performance.
What should growers be asking about seed treatments as we enter seed selection time? A lot of decisions about 2020 treatment are being made right now. This is the time to reach out to resources such as the SCN Coalition, have your fields sampled, and ask seed dealers what options they are carrying for next season to see if it fits your operation. Active management is going to be the most important factor to controlling SCN in 2020 and beyond. For more information, visit soybeanprotection.com.