It started a couple of weeks back on social media, but weather this week will increase the conversations even more: why wouldn’t I go ahead and put some beans in the ground?
Arguments can be made for and against early planting (another post for another day…), but what does seem consistent on both sides of the argument is: A soybean that emerges and begins to grow quickly generally tolerates disease/insect pressure better than one in cold, damp soils (if it survives – will it thrive?). Seed treatments are often used to help weather those cooler, damper conditions and while they do a great job, they have limitations. One is the active ingredient(s) in the treatment and what they will control. Another is the length of time they can provide some level of protection (approximately three weeks after planting give or take…)
One handy resource is Fungicide Efficacy for Control of Soybean Seedling Diseases from the Crop Protection Network. It provides some excellent information on various seedling diseases.
It also has some excellent information on seed treatments for a disease that infects the soybean plant early, but doesn’t show up until much later: Sudden Death Syndrome or SDS.
Increasingly an issue for NEK soybean growers over the past decade, SDS has shown the ability to survive not only soybean residue and in soil, but on corn residue as well. It survives our traditional rotations quite well and takes advantage of infection opportunities – most often when seedling development is slowed by cool/wet soil conditions. This graphic from K-State Extension Plant Pathologist Dr. Rodrigo Onofre illustrates some of those optimum infection windows:
While early planting does give us a better opportunity for SDS infection (that is when it’s typically cool and damp after all…), note that we often need a wet period later to trigger the infection symptoms. Its one of the features that makes SDS management difficult because we never know what we’re going to get from a weather standpoint – from infection all the way to visible symptomology.
Since we don’t know for sure what weather might throw at us, we often have to manage SDS in other ways. Start with the seed. Check varieties for SDS tolerance and use high germination seed when possible.
Good planting practices are also key. Research from the Kansas River Valley Experiment Field showed increased frequency of SDS foliar symptomology in narrow row spacings as compared to wider spacings.
Source: Dr. Rodrigo Onofre, K-State Extension Row Crops Pathologist
Because it’s a fungus, fungicide seed treatments have become popular as well. According to the previously referenced fungicide efficacy publication, there are multiple products labeled for SDS control. Unfortunately, many of the ones we might utilize for other diseases are rated poor for Sudden Death Syndrome – if they’re labeled at all. In fact, only two active ingredients – fluopyram and pydiflumetofen – are rated as very good for SDS control. Fluopyram is the active ingredient in ILEVO. Pydiflumetofen is the active ingredient in Saltro.
In 2023, K-State Extension Plant Pathologist Dr. Rodrigo Onofre tested both products in side-by-side comparisons with other seed treatments comparing all to an untreated check. While all seed treatments provide some positive yield difference, ILEVO and Saltro showed the strongest response.
Further evaluation by Onofre confirmed positive reductions in SDS root rot as well, either with Saltro by itself or ILEVO plus Ceramax, a biological seed treatment being tested with hopes of reducing the variability sometimes associated with seed treatments against SDS.
Soybean Sudden Death Syndrome isn’t a problem for every grower every year, tending to be a greater issue in well-managed soybean fields with a high yield potential, particularly when they have a history of SDS. In some cases, variety selection and planting management will keep SDS from being an issue, but if early planting or if planting conditions are favorable for SDS development, seed treatments could be an option to consider.
For more information on SDS management or K-State trials, contact me. Fungicide Efficacy for Control of Soybean Seedling Diseases are available upon request as well.
Alfalfa weevil growing degree days are accumulating fast! Come hear from KSU Field Crops Entomologist Dr. Jeff Whitworth as we discuss what to expect from some warm weather this winter plus hear results from product efficacy trials and application best management practices.