Freeze damage is showing up in at least two different ways in irrigated wheat as the crop nears harvest.
In some cases, the growing points of existing tillers were killed and new tillers began to grow. If the new tillers are mixed in with older tillers that survived, the result will be a field in which a portion of the heads are harvest-ready and the remainder are immature. In other cases, nearly all the existing tillers were killed and the field now consists almost entirely of new tillers. The uniformity will be better in this situation, but the grain will be maturing much later than normal and may not finish well, depending on how hot and dry it gets in late June and early July. In the end, yields and tests weights could range from better-than-expected (if temperatures are cool) to below average (if conditions are hot and dry from now through harvest). The green color in these fields may also be due in part to weeds that began to grow in fields where the main tillers were killed by the freezes.
In other cases, tillers showed significant damage, but the growing points were not killed outright. The lower stems may have been injured by the freezes. In this situation, the plants generally remained standing and the fields may have looked relatively normal for a while, although often becoming offcolor to varying degrees with time. Heads often began to turn white. In most cases this year, the white heads are not due to direct freeze damage to the heads. Rather, it is a delayed reaction to the lower stem damage that starved the developing heads of nutrients and water. Reduced yields can be expected.
Figure 1. In this field of irrigated wheat in Lane County, the lower stems were injured by the freezes. The heads turned white. This photo was taken June 19, 2013. Photo by Jim Shroyer, K-State Research and Extension.
Source : ksu.edu