Spring Weather Risks to Corn and Soybean Fields
Early-season planting brings opportunity, but it also comes with risk. Cold soils, fluctuating temperatures, and unpredictable spring conditions can expose newly planted corn and soybean seed to a range of early threats. From imbibitional chilling injury to frost damage, seedling diseases, and insect pressure, understanding these risks is key to protecting emergence and stand establishment while maximizing yield potential.
Imbibitional Chilling Injury Risks to Newly Planted Corn and Soybean Seed
Problem: Depending on the growing region, frost risks can persevere well into planting season and early growth stages. Planting into soil below 50 degrees increases the risk of imbibitional chilling injury to seeds. Seeds naturally swell during the first 24-48 hours after planting as they take in water and begin the germination process. However, when seeds and soil are cold, cell membranes are less elastic and swelling of the seed can lead to irreversible damage.
Solution: If soil temperatures are currently below 50 degrees or are expected to drop below 50 degrees for much of the 48-hour imbibitional window, consider delaying planting. After the imbibitional window passes, seed is much less susceptible to imbibitional chilling effects.
Frost Damage to Emerged Corn and Soybeans
Problem: Frost damage can be damaging or lethal to both corn and soybeans. Frost damage to corn is often less severe than frost damage to soybeans because the growing point of corn is further below the soil surface. However, in temperatures below 28 degrees, cold can penetrate 1-2 inches below the soil surface and kill the growing point in soil. Soybeans are more vulnerable to frost damage, as the growing point is above ground from emergence.
Solution: Cold weather can’t be prevented, so the most effective prevention measure for frosted corn and soybeans is careful planting timing. Monitoring soil temperature forecasts and avoiding planting into a window with a cold front forecast can help to prevent frost exposure risks on emerged plants. Low-lying areas of fields are more frost-prone than higher areas, so it’s important to take soil temperatures in the lower portions of fields.
Don’t be too hasty about replant decisions when frost damage occurs to corn and soybeans. Wait several days to determine what percentage of stand is affected to determine whether expected yield losses justify an entire replant.
Seedling Disease Risk in Various Spring Soil Conditions
Problem: There are a variety of seedling diseases which have damaging effects on seedling corn and soybeans – slowing and even potentially preventing germination and growth.
Phytophthora – Favored by wet and warm soils, this disease affects corn and soybean seeds by causing seed decay, pre- and post-emergence damping off, reduced stands and overall weaker seedlings. Soybeans are particularly vulnerable, as plants are affected at any growth stage leading to stem rot and wilting risk.
Pythium – This disease produces zoospores which travel through wet soils to directly infect plant roots. Corn and soybeans are susceptible to pythium, and infected seeds rot and damp-off, leading to poorer emergence and plant population.
Rhizoctonia – Favored by warm soils with moderate moisture, rhizoctonia is also more common when conditions are drier than those which favor phytophthora and pythium. Lesions on roots and stems girdle corn and soybean plants, leading to root and crown rot, stunting and seedling death.
Fusarium – Fusarium presents in both dry and wet soil conditions. Seedling risk from fusarium increases in wet and cool growing conditions. In these conditions, the disease leads to seed rot in the soil, post-emergence damping-off and overall damage to root system development.
Solution: Fortunately, there are several control options to reduce the risks of disease in seedling corn and soybeans. The first step is choosing hybrids and varieties with advanced disease suppression traits. Growers should also consider seed treatments containing active ingredients proven to provide protection against the disease they are most likely to see based expected field and weather conditions at planting.
Waiting for favorable planting conditions greatly reduces seedling disease risk. Avoiding planting in periods of cold rain reduces susceptibility of root rot, while also reducing vulnerability for other cold weather threats such as frost damage and chilling injury.
Cutworm Damage to Seedling Corn
Problem: Cutworm larvae typically damage corn from emergence through about V5 to V6 in the growth stage. The larvae initially feed on leaf tissue, which while visibly noticeable on the leaf blade as rows of small, circular holes, rarely impacts yield. The true damage occurs as cutworm larvae grow, and they begin to cut plants at or below the soil surface. Damage at this stage puts plants at a competitive disadvantage to surrounding plants and may lead to plant death if cutworm burrow deeper and damage the growing point. As corn and larvae mature, the cutworm larvae burrow into stalks and feed upwards, finally killing the plant.
Solution: Cutworm management can be based on prevention or use a curative strategy. Preventative tools to control cutworm populations include choosing traits with built-in insect control, using seed treatments containing neonicotinoid insecticides, and applying insecticides prior to emergence. Curative approaches must include regular scouting for early detection of cutworm damage. In fields where leaf feeding and/or cut plants exceed 5% with active cutworm, corn should be treated with approved insecticides to prevent further damage and plant death.
Key Takeaways for Early-Season Risk Management
Successful early-season crop establishment depends on managing risk as much as capturing opportunity. By paying close attention to soil conditions, weather patterns, and field-specific factors, growers can reduce exposure to early-season stressors and make more informed planting and replant decisions. A proactive approach which combines proper timing, seed and seed treatment selection, and field monitoring can help ensure stronger stands and set the stage for a productive growing season.
