December 24-28 was one of those freeze events that we do not often see in Valdosta. To some extent, every citrus variety has suffered from cold-damage due to this recent 5-night freeze event. The site of our citrus research plots at J.L. Lomax Elementary School in Valdosta reached a low of 16 degrees.
I recorded temperatures of 18, 20, 16, 21, & 22 degrees. I am sure other areas in southern Georgia were even colder. When temperatures are that low for that long there is not much that can be done to protect citrus and damage is to be expected.
It takes time to know the extent of damage that has occurred to citrus trees. Obvious early symptoms of damage are leaf curl and tanned foliage. After a few days many trees begin to shed leaves. Some green foliage that looks ok may also drop. Most of the foliage that is going to drop has likely dropped by now.
Shedding foliage is a good sign because trees and/or limbs that are killed by a freeze do not drop leaves. Foliage that turns tan and sticks to the tree indicates the limb or tree has damage or has died. It is common to see younger late season growth die back from freezes while older growth on the same tree appears ok.
Do not do anything to your damaged trees now. Do not prune trees now. We do not yet know the extent of damage to limbs, branches, and the trunks of trees. By May or June, limb damage will be obvious. Wait until then to prune dead limbs by pruning into the green wood just below the dead wood.
Any fruit left on trees was frozen and is no longer good. Frozen fruit is only good to use as juice but should be juiced within a couple of days after freezing.
Our winter has just begun so it is possible there will be more damaging freezes. With trees already damaged and with much less foliage, they will be more susceptible to freezes. For homeowner trees, the best way to protect your trees is with frost cloth that covers the tree and reaches the ground with a heat lamp underneath.
If that is not possible, wrap the trunk with a blanket and put a blanket over the tree. Some trees are too large for this. Also, trees with heavy fruit loads are more likely to suffer from cold damage. Trees can be banked with soil to where it covers the graft union but this is a good bit of work to pile up the soil around the trunk.
From my observations at this point, it appears the satsumas have handled the freeze the best. This is expected, as they are known for cold-hardiness and that is why many have been planted in Georgia. Lemons, grapefruit, and limes appeared to have the most damage. Everything else is somewhere in between.
At our citrus research site, Owari satsumas dropped about 50% of their foliage. All the foliage was damaged or shed on the Glen navel trees and the Sugar Belles. These trees received no cold protection at all, but all the trees were 10-13 feet tall. I expect some wood damage on these trees.
We freeze protected out Tango trees and they have retained 20-40% of their foliage and will no doubt have wood damage on younger branches. They were the youngest trees planted in 2020.
The silver lining to this 5-night cold snap is that we will learn which varieties are the most cold- hardy. There are at least 30 citrus varieties planted in Lowndes County. Another positive is that this cold weather will likely kill Asian Citrus Psyllids that may be trying to establish in Georgia. These tiny tropical insects transmit the deadly citrus disease called Huanlongbing (HLB), which has reduced Florida’s citrus production by about 75% since 2005.
Refer to the below publication from the University of Florida called “Freeze Damage Symptoms and Recovery for Citrus” for more info and some good photos of citrus damage https://edis.ifas.ufl.edu/publication/HS1275.