We are forecast to finally have some real winter over the next few days. Unfortunately, much of our wheat has already moved on to spring. Temperatures in Baton Rouge are forecast to reach 28–30 ˚F Saturday night. In Monroe (along I-20 in north Louisiana) temperatures are forecast to reach 22-24 ˚F, 18 ˚F at Greenville, MS, and 16 ˚F at El Dorado, AR.
The forecast has been in a state of flux over the past couple of days and it is hard to know what will really happen. I am pretty confident that we will have some freeze damage to wheat this weekend but it is difficult to predict how much. The good news is that it is still very early in the growing season, wheat has lots of time to recover, and wheat is a very resilient crop.
Wheat that is not jointed will not suffer anything more than superficial leaf burn at 20 ˚F. Our wheat has been growing very rapidly and there are lots of tender leaves that will have the tips burned, but this should not impact yield. Prior to jointing wheat is very tolerant of cold weather and damage is infrequent and superficial. Wheat becomes much more vulnerable to freeze damage as it progresses from first node to flowering. Hopefully we will have a cool February and not have to address that issue. There is really not much that can be done at this point. The chart below (borrowed from http://www.ksre.ksu.edu/library/crpsl2/c646.pdf)
shows the relationship between growth stage, temperature, and freeze damage. The months that correspond to the growth stages are appropriate for Kansas, not Louisiana. The growth stages are valid, except that tillering occurs all winter in Louisiana.
Wheat that has jointed (Feeke’s GS 6) will start to sustain significant damage around 24-26 ˚F. This damage can manifest in several ways. Stems can freeze on one side which weakens stems and can result in lodging at heading and poor grain fill due to inability to supply the developing head with adequate water and nutrients; or stems can completely freeze at the soft growing point resulting in loss of that tiller.
The link below is a good summary of spring freeze damage symptoms in wheat from our friends at Mississippi State. . http://msucares.com/crops/wheat/faq7_damage.html
The amount of damage on tillered wheat will depend on temperature and duration of exposure. I suspect that most of the wheat in Louisiana will only sustain superficial damage. I do know that there are some fields that have one and maybe even two nodes showing and these will be hurt. It normally takes a couple of days after a freeze before symptoms are easily apparent. This comes in the form of dead and dying tissue; lodging and discolored tillers; and a distinct odor of rotting tissue. Again, we won’t know the extent of damage until early next week and there is still a lot of time for the plants to form new tillers and make a near-normal yield. I’m sure the internet will be abuzz with freeze damage discussions next week