With the forecasted cool temperatures, perhaps a quick refresher is needed for the potential impact on Manitoba’s spring cereal crops.
Spring cereals such as wheat, barley and oats are very tolerant to temperatures as low as -6°C since the growing point is below the soil surface until the 5 leaf stage to jointing. In the May 21, 2015 NDSU Crop & Pest Report, Joel Ransom who is the Extension Agronomist for Cereal Crops, wrote there is “variation for tolerance between crops, however. In general terms for the cereals grown in ND (and provided they are at the same stage of development), tolerance to freezing temperatures can be ranked in the following order: winter rye (most tolerant to frost) > winter wheat > oats > barley > wheat > corn (least tolerant).”
Frost damaged spring cereals will have wilted, dark green and discolored leaves and will become necrotic at the leaf tips within 1 or 2 days after freezing. However, new leaf growth (normal green color) from the growing point should follow within 2-3 days. However, it can be upwards of 5 days if growing conditions remain cool after the frost event.
Fortunately, majority of emerged spring wheat, oats and barley acres in Manitoba are in the 1 to 3 leaf stages of development where the growing point is still below ground and therefore protected from the cool air temperatures.
For cereal acres that have recently been planted, but haven’t emerged, there is often concern cold and freezing temperatures can kill sprouted seed. In a 2015 article by Jochum Weirsma (University of Minnesota), he reports “literature has shown that sprouted wheat and young seedling will likely survive temperatures in the low twenties (20F = -6.7C). A quick first check of the color of radicle (first root) and coleoptile (first leaf) is the first step: a white and firm radicle and coleoptile will indicate that the sprout is not damaged by frost after the seed has been allowed to thaw out. A second test to determine viability of seed is to dig up seed and bring it home, place it between moist paper towels, and keep it at room temperature. If the seed is viable the sprouts should start to grow within 24 hours.”
And remember, temperature and crop type are only two factors that play a role in determining the impact of spring frosts – duration of temperatures, other weather conditions, soil moisture and residue cover can also have an impact.
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture