Back to November 2016

Invest in Your Native Pecan Trees

All too often I hear native growers complain that they have little or no crop because wet weather in the spring prevented pecan pollination. The truth of the matter is that a few rain storms during pollination rarely prevent nut set in native groves. When someone complains about lack of pollination, I immediately suspect the real problem is LOC disease. LOC disease is not a disease of the pecan tree but a disease commonly found among native grove owners. You see LOC disease is an acronym for Lack Of Care.

There are numerous causes of low crop yields in native pecans, many stemming from choices made by growers. One of the most common causes of low yield is an irregular or a complete lack of a fertilizer program. Pecan trees do not react to fertilizer application like row crops. In a field of corn, nitrogen fertilizer applied in the spring is returned as increased yield that same year. With pecan trees, it takes repeated, regular applications of nitrogen fertilizers to build up the tree’s nut producing capacity.

Added nitrogen does not increase the number pistillate flowers produced by a tree directly. Nitrogen fertilizer stimulates stem and leaf growth. With additional (and larger) leaves on the tree, a tree is able to capture more energy from the sun. That energy is stored in the tree and used the following year to produce pistillate flowers. Annual regular nitrogen fertilization has a cumulative effect on native pecan yield. In my experience, it takes at least 5 years of annual nitrogen applications before a previously neglected native grove reaches it full nut-bearing potential.

The lack of regular nitrogen application becomes obvious during the spring bloom period. Native trees that receive little or no nitrogen fertilizer might be covered in catkins but they will fail to develop pistillate flower clusters. If trees have minimum energy reserves to initiate pistillate flower clusters, they might develop female flowers clusters but the actual pistillate flowers are small and weak. These weak flowers never fully develop and are incapable of becoming fertilized.

As the pollination season progresses, these weak flowers fall from the tree. Some growers might look at this abortion of weak flowers as proof of their poor pollination theory. However, ill-formed pistillate flowers will never pollinate even under ideal weather conditions. Ultimately, the problem can be traced back to weak trees unable to create strong pistillate flowers. Only annual applications of nitrogen fertilizers can solve this problem.

Many native growers spend a lot of time scouting their trees for nut set and checking for signs of first-summer-generation pecan nut casebearer activity. Currently, most growers are getting the timing of their casebearer sprays right. However, once the trees are sprayed for PNC, it seems many growers forget to monitor their trees until it’s time to spray for weevils in August. Unfortunately, during many growing seasons a lot can go on up in the tree canopies that can lead to significant nut losses. This past summer provided a prime example.

During the summer of 2016 we experienced above average rainfall (that’s why I’m hearing complaints about pollination). The wet and humid conditions provided excellent conditions for the spread of pecan scab. Very few native growers have developed a pecan scab management plan for two reasons. First, fungicides are expensive, usually 3 times the cost of an insecticide application. Secondly, many growers use aerial applicators to spray their trees and, via past experience, have found that aerial application of fungicides are not effective. The thinking then boils down to — “Why should I spend all that money if the spray doesn’t work?”

By not addressing scab effectively, area pecan growers lost between one-fourth and one-third of their nut crop. Scab infections started as soon as the nuts began to increase in size and shortly after PNC appeared in the grove. Since we find a wide range of scab susceptibilities in native groves, losses due to disease vary greatly. However, this past summer, we found that roughly 20 percent of native trees began aborting massive numbers of scab infected nuts by mid-July. Additional losses to scab will become evident at harvest when scab induced stick-tights are thrown off the cleaning table.

Ultimately, native growers can limit nut losses due to scab by investing the time and money needed to effectively apply fungicides. It starts with abandoning aerial application and moving to ground rigs. However, it’s not as simple as changing spray application technologies. Fungicides need to be applied with enough water to ensure every nut on the tree receives a protective chemical coating. In addition, fungicides need to be applied before the disease becomes established on nuts.

In my years of managing native pecans, I have found that adding a fungicide to our PNC spray is an effective first step to protecting our nut crop. During wet years, like this past summer, we came back with a second fungicide application 2 weeks after the PNC spray. On rare occasion, we make a third fungicide application. My approach has been to prevent early scab infections on nuts because the earlier scab gets started the more serious the damage (nut drop and nut size reduction). I don’t think I’ve ever raised a 100-percent scab-free native crop using this approach but I’ve averaged 1,200 pounds per acre for over 30 years. Something must be working.

There is only one cure for LOC disease and that cure is investing in proper fertilization and pest control. The formula for raising consistent crops of native nuts is not rocket science; however, it does require that growers spend money and time on their trees. With improved prices forecast for the 2016 crop, native growers that have invested in their trees over a long period of time will be rewarded for their efforts. Growers suffering from LOC disease will be complaining to their buddies in the local coffee shop that their trees didn’t pollinate this year.

Author Photo

William Reid

William Reid is a horticulturist at the Pecan Experiment Field, Kansas State University, Chetopa, Kansas.