Growers have been contacting the Illinois Soybean Association asking about growing continuous soybeans. Soybeans require few inputs and have a lower product cost per acre than corn, so this is a very relevant question as we go into 2016. While growing continuous soybeans may not be the status quo, there are management practices that you can follow to have a successful growing season. In this article we will be focusing on using seed treatments to mitigate risks associated with continuous soybeans. It is important to remember that seed treatments alone cannot make continuous soybean production successful. Given that varietal selection is key, you need to consider which fields are best suited for this rotation, have a sound fertility program in place, and provide insect and weed control, all of which are all essential to the success of this rotation.

Growing continuous soybeans will cause a buildup of diseases and insects that will eventually result in yield losses. The top five yield-robbing pests in soybean production are Soybean Cyst Nematode (SCN); seedling diseases such as Pythium, Phytophthora, Rhizoctonia and Fusarium; Charcoal Rot; Sudden Death Syndrome (SDS) and Phytophthora root and stem rot that infect the seed during emergence. The total impacts of these diseases are noted in the table below. Other yield-robbing pests include bean leaf beetle, soybean aphid, wireworms, grubs and maggots. Based on the data below, you can understand why varietal selection and seed treatment go hand-in-hand.

Source: IPSOS Market Research

Navigating the world of seed treatments is extremely difficult. There are many products and combinations of products, and even more brand names. Based on the knowledge that disease, SCN and insect populations continue to increase in your continuous soybean acres, to be successful you will need to treat your soybean seed with a combination of products and there are a number available.

SCN builds up in the soil and rotating away from soybeans reduces the egg population in the soil. To combat SCN populations you will want to utilize a product such as VOTiVO™, Avicta™ or Clariva™. The control of SCN is essential to protecting your soybean plants’ root system. A damaged root system allows other diseases to infect your soybean, causing decreases in yields or plant death.

The SDS pathogen infects roots when the plant is emerging and when soils are cool and wet. To limit the yield losses associated with SDS, you will want to incorporate ILeVO™ into your seed treatment package. ILeVO seed treatment is currently the only seed treatment solution for Sudden Death Syndrome that also has activity against nematodes in the seed zone.

For the control of early season insects such as bean leaf beetle, soybean aphids, maggots and wireworms, use an insecticide such as imidacloprid (i.e., Gaucho™), clothianidin (Poncho™) or thiamethoxam (Cruiser™). Using an insecticide in your seed treatment will improve your soybean stand as more seedlings will reach establishment. A uniform, healthy stand is critical to year end results.

To combat seedling diseases you will want to use a fungicide seed treatment. The graph below is a helpful tool when selecting fungicide seed treatments for your soybeans. When talking with your seed specialist, agronomist or retailer you can determine which product or combination of products best fits your situation. For example, fluopyram (ILeVO) is the only product rated very good for the control of SDS, but you cannot rely on that seed treatment alone to control all diseases and insects. Today seed is treated with multiple fungicides to broaden control of soil-borne pathogens.

Ratings Fungicide Seed Treatments for Control of Seedling Diseases of Soybeans in the United States

Efficacy categories: E = Excellent; VG = Very Good; G = Good; F = Fair; P = Poor; NR = Not Recommended; NS = Not Specified on product label; U = Unknown efficacy or insufficient data to rank product. Please note: Efficacy ratings may be dependent on the rate of the fungicide product on seed. Contact your local Extension plant pathologist for recommended fungicide product rate information for your area.

Source: Identification and Biology of Seedling Pathogens of Soybeans, North Central Soybean Research Program

The yield and economic impacts of seed treatment vary year to year as a result of changes in disease and insect pressures, crop rotations, planting conditions and early growth conditions. Regardless of environmental impacts, it is a given in continuous soybean rotations that disease and insect pressures will increase and have a negative impact on yield and a strong seed treatment program is recommended. As these pressures increase the ROI for seed treatments will continue to increase. Work with your trusted advisor to select the best combination of products to reduce your risks and increase your profitability.

Lynda received her Bachelor’s degree in Agricultural Economics from the University of Illinois and has 21 years agronomy, ag technology, seed sales and crop protection experience.  Lynda is also involved in the family corn and soybean farm in southern Henry County with her dad and brother.