What is it?
Winterkill occurs when the crown of dormant wheat is damaged by freezing conditions. It is important to note that desiccated leaves make the plants look dead, but the crown may still be alive. See below on ways to assess plant health to determine if it is indeed winterkill.
Typically, the fields that are most affected by winterkill are those that:
- are planted on heavier clay soils
- are later planted with both low crown growth and depleted seed reserves
- have loose soil at planting, poor seed to soil contact
- have inconsistent snow cover during the winter
- have drainage issues, where water tends to pond or those where ice sheets formed in the winter
- experienced severe freeze thaw cycles especially in March and April
- experienced extreme cold without adequate snow cover.
Assessing the Damage and Treatment Options
When making assessments for winter survival, fields should be walked in late April to early May after growth resumes and fields green up. Assessing the damage, on a field scale, is key to deciding what to do with a field that has experienced winter kill. Fields are rarely affected uniformly.
Scout the field to determine how much of the field has poor or dead wheat. Physically walk the field in a W or Z pattern, counting the number of paces with no wheat or poor wheat for every 100 paces. This will give you a percentage affected. If 30% or more of the field is affected, it is best to replant to another crop.
Alternatively, 7-10 healthy plants per foot of row, in most cases, will produce 90-95% of yield potential if this population is reached on most of the field.
There are several ways to determine plant health:
- Dig up several plants with as many roots still attached as possible, shake each seedling free of excess soil; if soil adheres to roots, the root hairs are probably alive, as is the plant.
- Cut into the crown at the base of the plant and expose the tissue; if the crown tissue is white or light green, the plant is alive; if it’s brownish, it’s dead.
- The University of Nebraska recommends a plastic bag protocol: Remove the top three inches of soil containing plant crowns and warm samples to room temperature. Wash with cool water to remove attached soil. Cut off the leaves and roots to within an inch of the crown. Rinse the crowns with cool water, and then put 10 wet crowns in an inflated plastic bag and seal. Put the bag in a lighted room, but not in direct sunlight. Check the crowns in two days; rinse with cool water and re-inflate the bag. After four days, crowns that are alive should exhibit new root growth as well as new shoot growth.
How can I prevent it from happening again?
- Choose certified treated seed to ensure germination rates and protection from fungal pathogens.
- Choose varieties with strong winter hardiness scores.
- Planting date and good planting conditions are key to establishing a vigorous wheat stand that will make it through the winter.
- Plant winter wheat on fields with good drainage and minimal soil compaction.
- Target a planting depth of 1.25-1.5 inches to ensure you are seeding your wheat deep enough.
- A seed-placed starter fertilizer should be used to ensure vigorous early growth and root development.
Ensure good seed to soil contact when planting, ensure closing wheels are closing the seed trench.