Back to June 2024

Growers Observe Dieback in Trees Affected by Drought

A mature pecan tree greatly affected by drought. Dead limbs and brown leaves droop from the canopy.

A 'Pawnee' pecan tree in the summer of 2023 with dying limbs due to the drought and extreme heat. (Photo by Larry Stein)

Spring has definitely sprung, and most pecan trees are off and growing, though drought remains in many areas. Luckily, there has been rainfall to “green up” the landscape, but many well, river, and lake levels are dropping. Without significant rainfall, these levels will only continue to drop. 

We all remember what a vicious year 2023 was, with the lack of rain and unbelievable heat. Many trees had a great crop going into the summer of 2023, only to have the nuts drop due to the lack of water and extreme heat. Some limbs even succumbed to the situation. Hence, many trees went into the winter heavily stressed; we were unsure how those trees would look this spring. To the tree’s credit, many have come out in great shape; the key will be to see how long this trend will last.

I am starting to see dieback in the tops of many trees and even more trees pushing shoots from the lower trunk, meaning we also have limb dieback in many trees. The more intense the drought damage, the more tree dieback. Also, realize that stressed trees are much more susceptible to cold damage. For the most part, we had a fairly mild winter this year, except for one cold spell, but the cold damage was minimal.

So, what do we do now? There are several factors to consider. Has your water situation improved? What kind of catkin crop did you have, if any? Do you see nutlets? How are the trees coming out? Is there dieback in the treetops, and are shoots coming from the base? The answers to these questions will be crucial to how you move forward.

If your water situation has not changed, you are in a real dilemma, as you cannot afford to do business as usual. One of the things to consider would be to downsize, i.e., only concentrate on your best trees. If you have trees that are weak and not growing, then either take them out or do not give them any of your limited water. Perhaps there is an area in your orchard where the trees are weak due to poor, thin soil. These trees would be prime for removal. Also, consider immaculate weed control; it takes 80 gallons of water to grow 1 pound of weeds and grass. If the weeds do not get the water, perhaps the trees will. 

Once you have the weeds in check, consider mulching. Yes, mulching can get in the way of harvesting, but it could go a long way to conserving water and keeping your trees healthy. Double-shredded hardwood makes a great mulch, as it will eventually break down to compost.

If your catkin crop was amazingly strong, you are potentially poised to have a large crop. So, you will want to scout your trees and determine how many shoots out of ten have clusters. If the number of shoots with clusters is greater than five, you may want to let the pecan nut casebearer harvest some pecans. In this way, the tree will have fewer nuts to support if the weather conditions do not change.

An orchard suffering from dieback after extreme drought.

Photo 1—A pecan orchard with limb dieback. (Photo by Larry Stein)

Growers are observing various stages of tree growth this spring, as shown in the pictures here. The first photo is an example of Pecan Orchard Limb Dieback, which is showing up in many orchards, where the limbs have died back to the buds, limbs they can support. The good news is that in many situations the new shoots are quite healthy, like in the second photo. If this is the case, the old dead shoots can be removed. Although these shoots can be left, the limb removal makes the trees look better. If you do prune, cut them back to the strongest shoots.

In other cases, we have major limbs dying, like in photo 2a, which again the drought caused. Often, in these home landscapes, we see all the pecan trees die when no one no longer lives in the house.

Photo 3—The limb dieback on this pecan tree appears to be the result of drought, but cut ants could also have caused it.

In some cases, we see the dieback in photo 3, which appears to be the result of drought but could have been caused by cut ants feeding, which can lead to the limbs dying back. Cut ants typically affect smaller trees but can feed on larger ones. Spraying contact insecticides should keep the ants in check. Small, newly planted trees are the most susceptible trees to cut ant damage; many times, such trees do not recover from such damage.

Cut ants damaged this large pecan tree which has several leafless limbs.

Photo 4—Other factors besides drought can lead to dieback. Cut ants caused limb dieback on this pecan tree. (Photos courtesy of Larry Stein)

We are also seeing many young grafted trees die, like in photo 5. It’s just heartbreaking. Even though there is still a bit of life in the rootstock, the tree is definitely on the decline and will more than likely die.

A young pecan tree with no leaves during the spring due to extreme dieback from the previous drought.

Photo 5—Young, grafted trees are most susceptible to drought. Many growers are seeing dead trees like this one because of last year’s drought.

Often, the most puzzling thing to many growers is how some of these native trees, photo 6, are dying. The tree in this photo is 200-plus years of age and sits on 20-plus feet of soil by the river. The river did not go dry, but as of early May, it is not running. Many wonder how such a tree could die when surely it has roots near the river. Interestingly enough, many of these older trees also died in the drought of the ‘50s. Basically, a clay layer near the river leaves the tree roots in a “bowl,” so to speak, and they can no longer access water in and around the river. Several years ago, when there were massive numbers of larger trees dying in the San Saba area, the soils around these trees that were dying were cored, and we found that the soil was powder dry to the gravel layer.

An ancient native pecan tree killed by the drought. The branches are completely bare even in early summer.

Photo 6—Drought can kill even trees in river bottoms. This 200-year-old native pecan tree was killed by the drought. (Photo by Larry Stein)

It is really tough to witness the current feast and famine as rainfall continues across our state. Some areas are totally flooded, and others remain bone-dry. Here is hoping the weather pattern will return to a more regular rhythm and that drought-stressed trees will recover. If there is a silver lining, it could be that the effects of the drought give us the incentive to take out trees that need to go!

Author Photo

Larry A. Stein

Larry Stein is a professor and Extension Specialist for Department of Horticultural Sciences at Texas A&M University.