By Delbert Voight
Many winter grains in southern PA are currently in a susceptible growth stage and we have now had two nights of hard freezes that could impact their yield potential. What does that mean?
Winter grains are currently in a susceptible growth stage and we have now had two nights of hard freezes that could impact their yield potential. It might be a good idea to print off this fact sheet and review what to expect. In as little as 2 hours of a freeze below 30 the result could impact the crop yield of this 2016 crop as it has progressed beyond normal growth from early seeding last fall. As it begins to form the head at jointing stage it must be protected from weather, pests and nutrient deficiencies. Here is a photo from Extension Specialists from Purdue of some tip burn from some wheat in the jointing stage that received a night at 30 degrees back in 2012 that is very similar to conditions we had last night. This has little impact on yield. In 2012 another freeze occurred at the heading stage and that resulted in alot of damage to the wheat crop in Indiana. It takes time to really assess these fields perhaps 10 days to really know and assess damage. Time will tell how deep the freeze occurred and the impact on the head.
Here is a picture of what the plant is doing right now at jointing with the hollow stem and the small seed head forming above that point. (Source Arkansas University Extension) I was involved in some cases where liquid nitrogen applications burned the wheat below the head and this resulted in a complete loss in the fields that were burned by the liquid N. This would be similar to this situation if the freeze reaches and destroys the tender seed head inside.
Dr Chad Lee in Kentucky has a nice factsheet detailing wheat and freeze damage. The table below is an excerpt from his writings and it provides the temperature and hours to become an issue. Freeze damage affect on Wheat
Table 3-3. Freeze injury in wheat.*
| Growth stage | Feekes | Zadoks | Approximate injurious temp. (2 hrs) | Primary symptoms | Yield effect |
|---|
| Tillering** | 5-Jan | 20-29 | 12°F | Leaf chlorosis; burning of leaf tips; silage odor; blue cast to fields | Slight to moderate |
| Jointing | (6-7) | 31-32 | 24°F | Death of growing point; leaf yellowing or burning; lesions, splitting, or bending of lower stem; odor | Moderate to severe |
| Boot | 10 | 41-49 | 28°F | Floret sterility; spike trapped in boot; damage to lower stem; leaf discoloration; odor | Moderate to severe |
| Heading | 10.1-.5 | 50-58 | 30°F | Floret sterility; white awns or white spikes; damage to lower stem; leaf discoloration | Severe |
| Flowering | 10.51-.54 | 60-71 | 30°F | Floret sterility; white awns or white spikes; damage to lower stem; leaf discoloration | Severe |
| Milk | 11.1 | 75 | 28°F | White awns or white spikes; damage to lower stems; leaf discoloration; shrunken roughened or discolored kernels | Moderate to severe |
| Dough (11.2) | 11.2 | 85 | 28°F | Shriveled discolored kernels; poor germination | Slight to moderate |
| *Information in this table assumes timely rainfall events occurring after the freeze event. |
Frost can also impact other crops as well. The tips of alfalfa might get frosted off but the most severe impact will be from small grains that are now for the large part in the jointing stage.
So the action is to wait and see what the plant tells you in the next week to determine if the freeze impacted the head development.