FAQ About Pecan Production in the Home Garden

Prepared by Mark Arena, Specialty Crop Agent, Clemson University, 07/17.

HGIC 1362

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Question: Are pecan trees native to South Carolina?

Answer: Many believe that pecans are native to South Carolina; however, the reality is they are not. Pecans are native to North America, and their natural range includes several states such as Texas, Oklahoma, Arkansas, Mississippi, Louisiana, Missouri, Illinois, Indiana, Ohio, and parts of Wisconsin. Pecans probably made their way to South Carolina through commerce trade and were planted by the colonists in the late 1600s.

Pecans (Carya illinoensis) were first planted in S.C. by the colonists in the late 1600s.
Pecans (Carya illinoensis) were first planted in S.C. by the colonists in the late 1600s.
Photo courtesy of Yon Family Farm, Ridge Spring S.C. ©2016

Question: Will pecan trees produce a viable crop each year?

Answer: Pecan trees do not typically produce a dependable and significant crop each year. In reality
homeowners are lucky if they get a good crop of pecans every four or five years. The reasons being:

  1. Pecans require a lot of water. On average, a pecan tree requires 1 to 2 inches of water per week.
  2. Disease pressure reduces the vigor of the tree and impacts the nut quantity and quality.
  3. Most pecan trees are known as alternate bearing trees, which means they are only capable of producing a dependable crop every other year.
  4. Most trees are not properly fertilized. Trees should be fertilized using the recommendations from a soil analysis.

Question: What pecan disease is most frequently encountered in South Carolina?

Answer: Pecan Scab is the most common and destructive disease to impact pecan trees and their nuts. Between the rainy weather and the presence of this commonly occurring disease, it is a challenge in South Carolina to produce pecans that are not infected. Scab infects all parts of the tree including the leaves, branches, and nuts. Rain rapidly spreads the disease from leaf to leaf. Most fungicides available to a homeowner are not effective.

Many advertisements make claims that certain varieties of pecans are resistant to disease. In reality there is not one variety available that is completely or reliably resistant to diseases. Scab severity is based on the pecan variety to some degree, but more importantly on weather. The more it rains, the worse the disease becomes. It thrives in hot, humid climates where moisture and dew remain on the leaves and nuts for an extended period of time.

Pecan leaf and nut are infected with the fungus (Cladosporium caryigenum) which causes pecan scab.
Pecan leaf and nut are infected with the fungus (Cladosporium caryigenum) which causes pecan scab.
Mark Arena, ©2014, Clemson Extension

Question: How should homeowners manage pecan diseases?

Answer: The challenges for homeowners are how to properly manage their tree or trees for nut production in a safe and economical manner. First is safety. Pecan scab can rarely go unmanaged, especially if it is a rainy summer. There is no easy way for a homeowner to treat diseases in a safe and cost- effective manner. The only way to successfully treat for a disease is to use a high-pressure sprayer. The price of the equipment and the appropriate fungicides cost thousands of dollars. In addition, the amount of spray drift that would occur makes it impossible to use this type of equipment in most residential settings. There are no economical products legally available. The use of any systemic products (that is, using fungicides that would go into the foliage and nuts) are illegal and cannot be used for human consumption.

The weather plays a key role in pecan disease management. Wet, rainy summers lead to poor pecan production in most cases. The following are ways to potentially improve nut production:

  • If possible, provide one to two inches of irrigation water per week during the growing season.
  • Properly fertilize the trees based on a soil analysis.
  • Do not park or drive under the crown of the pecan tree.
  • Once the tree has completely defoliated in the fall, rake up and dispose of all the leaves, twigs, and nuts.

Question: What is the best way to fertilize a pecan tree?

Answer: Many believe that using a simple, common approach to fertilizing is acceptable. This approach can cause more harm than benefit. The method of applying a certain number of pounds of fertilizer per inch of tree diameter/caliper is not recommended. Scientists now understand that this approach can potentially lead to excessive phosphorus in the soil, which negatively affects nut production and ground water. This also holds true for the use of special fertilizers specifically advertised for pecans. Many of these fertilizers have zinc sulfate incorporated into the blend. Zinc is a trace element that pecans require; however, research has revealed that the problem is that the tree roots struggle to absorb this element. No matter how much zinc is in the soil, the roots can only absorb so much. Therefore, in most cases, the roots fail to take up an adequate amount of zinc. In commercial production, pecan trees are sprayed with a form of liquid zinc to overcome this lack of root absorption. The best and most environmentally friendly approach for fertilizing is to have a soil analysis conducted and follow the recommendations noted in the report.

Question: How important is water for pecans to produce nuts?

Answer: Pecans are native to river and stream bank areas where they have access to plenty of water. During the growing season, mature bearing trees can require up to two inches of water per week depending on the soil type and age. This equates to approximately 100 gallons of water per tree per week. Therefore, if the trees are not receiving adequate water, the quality and quantity of nuts will be impacted. This presents two challenges for homeowners. First is the cost of city water and second is the ability to supply the proper amount of water. The best method is through a sprinkler that slowly delivers the water to prevent run-off.

If pecan trees are not receiving adequate water, the quality and quantity of nuts will be impacted.
If pecan trees are not receiving adequate water, the quality and quantity of nuts will be impacted.
Photo courtesy of Yon Family Farm, Ridge Spring S.C. ©2016

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This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.