The last couple days the weather has given us some dry sunny weather with high winds. This has been great to have fields finally dry off and make strides with planting the crop. Unfortunately this also exposed young small grain seedlings to same conditions. The daytime heat at the soil surface has caused heat canker. The tender young tissue at the soil surface basically has been 'cooked' and this appears as a yellow band that is slightly constricted (Photo 1). As the leaf continues to grow, this yellow band (1/8 - 1/4") moves upward and away from the soil surface. If the hot and dry weather last for several days, repeated bands should become visible. The damage is nicely depicted on page 81 of the second edition of the Small Grains Field Guide. Because of the high winds, the tips of leaves may break off at the yellow band and give a field a very ragged appearance. Damage from heat canker is temporary and should not affect further growth and development.
Photo 1 - Wheat seedlings with the yellow, constricted
appearance symptomatic for heat canker
(photo courtesy of Luke Steinberger)