Due to the low commodity prices, Michigan soybean producers want to know if seed treatments are consistently profitable. Because of this, they identified seed treatments as a high priority for evaluation in on-farm research trials. Three research projects were designed to evaluate the yield and income benefits of seed treatments available for soybeans.
The first project ran from 2014 to 2018 and compared a base fungicide/insecticide seed treatment with and without Clariva pn as it is not a stand-alone treatment. Clariva pn contains a naturally occurring soil bacteria (Pasturia nishizawae) having a direct mode of action on soybean cyst nematodes. The goals were to determine how the product affected soybean cyst nematode population development and soybean yields. The Clariva pn did not suppress soybean cyst nematode development at the four locations infested with soybean cyst nematodes and it did not increase soybean yields in any of the seven trial locations.
ILeVO seed treatment is marketed as having activity on sudden death syndrome and soybean cyst nematode, both of which are increasing in Michigan. ILeVO was tested in 19 trials conducted from 2016 to 2018. Like Clariva pn, ILeVO is not marketed as a stand-alone seed treatment, so we compared a base fungicide/insecticide seed treatment with and without ILeVO at all locations. When all 19 sites were combined, the ILeVO increased soybean yields by 1.9 bushels per acre despite very low levels of above-ground symptoms of sudden death syndrome in any of the trials. Again, like Clariva pn, ILeVO did not significantly suppress soybean cyst nematode development.
The purpose of the third on-farm research project evaluating seed treatments was to provide an opportunity for cooperators to evaluate the performance of the base seed treatment of their choice on their farms in 2017, 2018 and 2019. This trial compared two treatments (a base seed treatment including multiple fungicides plus an insecticide versus untreated seed from the same seed lot).
The base seed treatments increased soybean yields at nine of the 29 locations with the yield increases ranging from 1.2 to 10 bushels per acre. However, the seed treatments were profitable at only five of the locations. When all 29 sites were combined, the seed treatment increased yields by 1.3 bushels per acre. This is slightly less than the 1.5 bushels per acre required to recover the cost of a basic fungicide plus insecticide seed treatment costing $14 per acre. The base seed treatments also increased final plant stands by 4,500 plants per acre when all sites were combined.
In summary, Clariva pn and ILeVO seed treatments are not the most effective tools for managing soybean cyst nematodes as they did not suppress soybean cyst nematode development. More effective soybean cyst nematode management strategies are available, including prevention, early soybean cyst nematode detection through regular soil sampling and testing, rotating with non-host crops and careful selection and use of soybean cyst nematode-resistant varieties based on field-specific soybean cyst nematode type testing.
ILeVO provided the highest yield increase of all the seed treatments tested when averaged across all locations and has a high probability of being profitable when used in fields having a history of moderate to severe sudden death syndrome. The base fungicide/insecticide seed treatments provided modest yield increases when averaged across all locations but should be used when planting early into fine-textured soils that are cold and wet, when planting into grass sods and when manure or green plant material has been incorporated into the soil within two weeks of planting.