By Dr. Clark Neely, Small Grains Extension Specialist, College Station | 979-862-1412 | cbneely@tamu.edu
Dr. Reagan Noland, Regional Extension Agronomist. San Angelo | 325-657-7330 | Reagan.Noland@ag.tamu.edu
Recent cold temperatures experienced across the state are causing some alarm for wheat producers. On the morning of Tuesday March 5, low temperatures ranged from near 10oF in the northern Panhandle to mid-teens in the Rolling Plains, low 20’s for much of the Blacklands and mid to upper 20’s for areas of South and Southeast Texas (Figure 1). Most of the wheat in the High Plains and Rolling Plains has not yet begun to joint, which is the point at which stems begin to elongate and the growing point is elevated above the soil surface. Once jointing initiates, growing points are more susceptible to cold damage (Figure 2). Therefore, freeze damage is unlikely at this point for those regions.
Figure 2. Low temperatures across Texas for March 5, 2019 (Graph adapted from A.W. Pauli).
There have been numerous reports of wheat plants with growing points 4-6” above the soil in parts of the Blacklands this past week. Freeze damage can occur at approximately 24oF if sustained for 2 or more hours, thus injury is possible in this region since temperatures dipped to near 20oF in many locations. Many of these fields were planted to hard red winter wheat variety ‘WB Cedar’ which is an earlier maturing variety. Other popular varieties such as ‘TAM 304’ and ‘Coker 9553’ (soft red winter wheat) are medium maturing and likely less advanced in growth stage.
It is important to note that freeze damage is dependent on multiple factors including not only minimum temperature and growth stage, but also freeze duration, wind, topography, and soil moisture.
Figure 3. Healthy growing point of wheat (Photo courtesy of Clark Neely.)
When scouting fields, it will likely take at least a week before visible symptoms appear, particularly when temperatures remain cold following the freeze event. Warm temperatures return to much of the state by Thursday and last through the weekend, so symptoms should be visible by next week. Leaf burn is likely throughout the Blacklands and possibly further north, but it does not necessary correlate with growing point death. Leaf burn by itself should not impact yield, unless it occurs to flag leaves. The best way to scout for growing point death is to using a razor or knife and split the stem length wise. If the growing point is dead, it should be brown and mushy instead of green and turgid (Figure 3).
If growing point damage has occurred to the primary tiller this early in the season, it is likely that the plant can compensate by rerouting resources to secondary and tertiary tillers if water and nutrients are not limiting. If damage were to be more severe (more tillers are affected) or occurs later in the growing season, producers may consider harvesting for hay or grazing out rather than taking for grain. However, such extensive damage is not anticipated at this time from the most recent freeze event. For more information on assessing freeze damage in wheat, please refer to Texas A&M AgriLife Extension publication “Wheat Freeze Injury in Texas”.
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