Soybean Seed Treatments Add Protection Against Pests

• All seed treatments are not created equal.
• Understanding the active ingredients in seed treatments is key to understanding which pests will be controlled and which seed treatment your soybeans need.
• Seed treatments are the first line of defense against pests. Yield lost to seedborne pests can never be recovered.

Pest Management with Seed Treatments

Farmers are planting soybeans earlier to capture the full growing season for additional soybean yield potential. In some areas of the Midwest, farmers have been planting soybeans as early as late March or early April. Often the soil is cooler and wetter during early planting windows, resulting in slower soybean germination and emergence. As the length of time a soybean seed is sitting in the ground increases, so does the vulnerability of the seed to pests.

Seed treatments protect soybeans against pests such as insects, diseases and nematodes. Common insect pests include aphids, bean leaf beetles, leafhoppers, seedcorn maggots, white grubs and wireworms. Diseases such as Fusarium, Phytophthora, Pythium, and Rhizoctonia often impact soybean yield potential.

Soybean Seed Treatment Trials

Golden Harvest conducted Agronomy in Action research trials at 8 locations in the 2022 growing season to evaluate the value of seed treatment options across a range of environments. 8 different insecticide and/or fungicide combinations were evaluated for differences in stand establishment and yield. Treatments were designed in a way to understand the incremental yield response when additional active ingredients were added (Table 1). Vibrance^® Trio seed treatment is solely comprised of fungicides, whereas CruiserMaxx^® Vibrance seed treatment contains the same 3 fungicides with the addition of CruiserMaxx (thiamethoxam) insecticide. CruiserMaxx APX seed treatment contains the same insecticide/fungicide rates and active ingredients, along with an additional fungicide (picarbutrazox) to provide a second mode of action for managing Pythium and Phytophthora species. Acceleron^®, an insecticide and fungicide combination, was also included as a competitive check to compare relative performance. Saltro^® and ILEVO^® fungicides were added to select treatments when sudden death syndrome (SDS) was present.

Trials established at Blue Earth, MN, Clinton, IL, Slater, IA, and Waterloo, NE, experienced relatively little observable insect or disease pressure throughout the season, resulting in very small yield differences between treatments at those locations (data not shown). Larger treatment differences were observed at other locations and results were highly dependent on specific pests present.

Location with Insect and Phytophthora Present

The Clay Center, KS, site experienced a substantial number of overwintering adult bean leaf beetles (BLB) soon after emergence causing significant defoliation (Figure 1). All treatments lacking a seed-applied insecticide were easily recognizable prior to crop canopy due to the early feeding damage. The insecticide component in CruiserMaxx Vibrance and CruiserMaxx APX provided excellent control of BLB feeding compared to Vibrance Trio, which did not include an insecticide. Plants treated with CruiserMaxx Vibrance and CruiserMaxx APX were visually healthier and more robust early in the growing season (Figure 2). Plants emerging from seed treated with Acceleron, which uses imidacloprid insecticide, had less BLB damage than non-insecticide treatments, but slightly more damage than observed in plants where seed treatments included Cruiser^® insecticide. Overall, adding insecticide to fungicide increased yield by 7.4 bushels per acre (bu/ac) when comparing Vibrance Trio to CruiserMaxx Vibrance seed treatment, largely due to BLB presence (Graph 1).

Soils at Clay Center warmed rapidly after planting but remained saturated from early rains, resulting in ideal conditions for Phytophthora to develop. Phytophthora symptoms were observed in plots planted to a susceptible variety neighboring the seed treatment trial, suggesting that Phytophthora was likely also present in the more tolerant variety within the seed treatment trial. Phytophthora presence likely produced the 6.5 bu/ac CruiserMaxx APX advantage over CruiserMaxx Vibrance and the 12.6 bu/ac advantage over Acceleron seed treatment (Graph 1).

Locations with SDS Foliar Symptoms

Soybean plants at Jefferson, WI, Malta, IL, and Sac City, IA, all showed varying levels of foliar symptoms of SDS. Jefferson had the most severe SDS symptoms, and plots that were treated with Saltro could be visually distinguished from plots that were not (Figure 3). Saltro provided excellent control against the interveinal chlorosis symptomology of SDS whereas ILEVO reduced symptoms some, but not as consistently across replications.

Adding Saltro to CruiserMaxx APX increased yield 5.2 bu/ac, whereas adding ILEVO to Acceleron only added 1 bu/ac at the Jefferson site (Graph 2). Although present, SDS symptoms were less visible at Sac City and Malta locations. Due to low SDS presence, less differences in yield were observed when Saltro or ILEVO was added to their respective treatments (Graph 2).

Summary

When including the 4 without pest presence and averaging across all 8 locations, incremental yield benefits from adding insecticide and new fungicides are still seen. On average, adding a base fungicide and then an insecticide increased yield by 1.9 and 1 bu/ac, respectively. Benefits from Saltro decreased when averaged across locations since 5 of 8 locations did not have SDS present, although added 0.5 to 5.2 bu/ac at locations with symptomology. Ultimately the highest yield potential was seen when the complete seed treatment package (CruiserMaxx APX + Saltro) was used in combination with Miravis^® Neo foliar fungicide applied at the R3 timing to provide a season-long disease protection program (Graph 3).

Results from this study show the benefits of protecting the seed with specified seed treatments when specific pests are present. In-season pest pressure is not always known by the time seed treatment decisions need to be made. Since pest presence is highly dependent on that year’s weather events, seed treatments may not always show responses. As a result, understanding relative risk of specific pests and matching that to the best combination of treatment options is important in determining profitability. Yield losses from seedborne pests can be significant so protecting seed investment with seed treatments is important.

If you have questions about soybean seed treatments, please reach out to your local Golden harvest Seed Advisor or agronomist.