Desirable Foliage & Bark Issues

I am seeing nuts forming on trees in Thomas County and dry weather has helped lessen scab severity. All orchards have sprayed two or three times by now – some more. Here are some notes from UGA Extension Horticulturalists Dr. Lenny Wells on some issues he has had calls about in Desirables. We may observe leaf drop and bark flaking, but this is not much concern.

Bark Flaking Off

Bark Flaking-Photo by Dr. Lenny Wells

Bark Flaking-Photo by Dr. Lenny Wells

I get calls every year about ‘Desirable’ pecan trees on which the bark is peeling off or sloughing off in large chunks. While it occurs on other cultivars, this is a common occurrence and yet another quirk of ‘Desirable’. When trees grow in diameter the older, outside bark can’t stretch. This is why, on younger trees, the outer bark cracks as they grow. The shape and pattern of these cracks are genetic traits of the tree and varies by cultivar. Older trees with scaly bark simply slough off bark. This process is helped along at times by woodpeckers searching for a meal of insects under the bark.

When large chunks of the bark slough off, it can be alarming to see, but it is nothing to worry about. This is simply a natural part of the tree’s growth process. Its just the outer layer of bark coming off, revealing a cinnamon-colored younger bark below, which will eventually take on a normal appearance as the tree continues to grow. This is often confused with lightning damage. As long as the bark doesn’t come completely off, revealing the wood (which will have a smooth, white appearance) underneath, the tree is fine.

Leaf Drop

I’ve also had a few calls in the last day or so regarding the dropping of leaves from ‘Desirable’ trees. This is an annual occurrence and is a physiological condition we see more pronounced when there is a fast change in environmental conditions as we’ve seen recently with a shift from cool and wet to hot and dry weather. ‘Desirable’ is more sensitive than many other cultivars to this and many other problems. Last year, this occurred in early June but the tree’s foliage/crop development as well as the shift in weather conditions has occurred earlier this year. This is something that seems to happen every year. Much of this minor leaf shed is simply the dropping of shaded leaves in the interior of the tree. A good, look at ‘Desirable’ trees often reveals a fair amount of bare limbs on the interior of the tree that the tree simply self-prunes.

At any rate, this early summer green leaf drop by ‘Desirable’ is largely inconsequential and doesn’t really pose a problem. It is simply a physiological response of the tree and is not related to a nutritional problem. It occurs each year and if you do not notice the defoliation when looking at the tree from a distance, but only see it when you look under the tree, there’s no worry. Growers with ‘Desirable’ in 2014, have more to worry about in the form of scab than they have in a minor leaf drop.

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