Johnston, IA (April 21, 2025) - Early planted soybeans often equate to high yields. However, early planting comes with inherent risks. Several pathogens that attack soybean seeds and seedlings — Phytophthora, Pythium, Rhizoctonia and Fusarium — survive in the soil and diseased plant material.

These diseases are most common in the first few weeks after planting, especially in heavy, poorly drained, compacted or high-residue fields. One of the most damaging and persistent diseases in early planted soybeans is sudden death syndrome (SDS). SDS ranks as one of the top diseases in terms of economic impact. Yield losses can be significant due to several factors:

  • Root rot, which limits the plant’s ability to take up water and nutrients
  • Leaf tissue necrosis, which reduces the plant’s ability to photosynthesize effectively
  • Pod abortion and smaller seed size, both of which directly impact the final yield

“All of these combined factors can lead to yield reductions of up to 50% when SDS is present,” said John Richards, Pioneer Field Agronomist for southeastern Michigan. Additionally, the presence of soybean cyst nematode (SCN) can worsen SDS symptoms by creating infection pathways that allow the pathogen to easily infiltrate the plant. A Pioneer trial conducted in southwest Michigan from 2011 to 2013 illustrates this relationship. In a field with heavy SDS and SCN pressure:

  • Varieties with Peking resistance outyielded varieties with no SCN resistance by 36 bushels per acre
  • They also outyielded varieties with the traditional PI88788 resistance by 14 bushels per acre

Soybean Protection 

Seed treatments should also be considered when SDS has been identified in the past. Certain treatments protect against both fungal pathogens and nematodes. The fungicidal properties help shield the seed and seedling from the SDS fungus, which is soilborne, while the nematicide component reduce infection sites caused by SCN, indirectly lowering the risk of SDS infection.

In a recent Pioneer® trial series, adding ILEVO® HL seed treatment on top of the premium package of Lumigen® seed treatment resulted in a 3.88 bushel per acre yield increase. However, Pioneer Field Agronomist John Richards says the best chance of success against SDS is still varietal selection. “You want to choose a variety that has a high SDS score,” he said. 

The Sniff Test 

“When soybeans are planted early, I like to check seed viability after a couple weeks,” said Bradley Mason, Pioneer field agronomist in Illinois. “Follow the path of the planter and dig a small trench to inspect the seeds.” 

Mason suggests examining a few seeds to see if they’re intact, then squeezing them to check for firmness. 

“If the seed feels mushy or gives off a rotten smell, it’s likely not viable,” he explained. 

If the seeds appear healthy, continue monitoring until emergence.