Much is made about winterkill on the Canadian Prairies. In reality long term Crop Insurance data shows that incidence of winterkill is approximately 9%. To help put this in perspective, Kansas, the largest winter wheat producing state in the U.S. has an incidence of winterkill of 9%!

Assessing Winterkill

A proper spring assessment is an important management tool in successful winter wheat production. In too many cases, winter wheat crops are destroyed before the crop has time to adequately recover. Assessing the crop condition early in the season can be difficult as brown leaf material may not be a sign of winterkill and green leaves may not mean the crop has survived.

A quick and effective way of assessing viable plants can be to remove a few plants on a warm day and place the crowns in a wet paper towel in a warm room that will be exposed to light for part of the day. Since winter wheat crops regenerate and start growing from crown tissue, healthy tissue will remain white and start to produce new roots, and damaged crown tissue will quickly turn brown. The best time to assess crop condition is as late as possible, after the bulk of spring seeding has been completed. This gives the winter wheat plants time to re-grow while still allowing time to re-seed if necessary. This generally means assessing the crop between May 15^th and 25^th.

Plant Populations

The optimum winter wheat plant stand is 20 to 30 plants per square foot; however, lower plant populations will still produce an adequate crop as this comes from its exceptional ability to tiller. The challenge when assessing spring establishment can be that winterkill usually occurs in patches. As shown below, thin stand populations still have the capacity to produce very profitable crops.

Winter Wheat Yield at Different Stand Densities

*from Lafond and Gan, 1999

Spring Management

Timely management in the spring is very important to the success of a winter wheat crop. In situations where the stand is thin or weak, a more intense management strategy is required. A thin plant stand is typically less competitive against weeds, requiring more attention to broadleaf and grassy weed control. Nitrogen should be applied as soon as possible in the spring to encourage the remaining plants to tiller and produce a healthy stand.

Re-Seeding

Only when the stand has been properly assessed and deemed unacceptable should a producer terminate the winter wheat crop and re-seed. If the decision is made to re-seed, consider the following management practices:

• Determine if a late seeded crop will produce a higher profit potential than a poor or thin winter wheat crop.
• If the winter wheat was treated with 2,4-D in the fall, re-seeding a broadleaf crop may not be an option due to sensitivity of chemical residues;
• Spray out the winter wheat as the crop will draw on moisture and nutrients reserves;
• Avoid replanting to cereals, especially wheat – Wheat Steak Mosaic may carryover from infected winter wheat into spring-seeded cereals; if replanting to wheat, a 10- to 14-day window should be left before reseeding to avoid problems;
• Remember to credit any spring-applied nitrogen to the following crop.

Summary

With winter wheat it is important to remember to give the crop time to recover in the spring before performing a proper assessment. Thin plant stands still have the ability to produce a successful crop; however, proper spring management practices should be considered, such as management of weeds and early application of nitrogen. If the decision to terminate the winter wheat crop was decided, remember some broadleaf crops are sensitive to fall applied 2,4-D, avoid replanting of cereals, as diseases can carry over and credit any spring applied nitrogen to the following crop.

For more information click here for a video on Winter Wheat Spring Assessment

By Amanda Swanson