For many generations, people have grown pecans on family homesteads in North Carolina for both food and profit. Today, there is a renewed interest in growing pecans in North Carolina, predominantly in the southeastern part of the state. Growing pecans requires patience and a long-term commitment. With some effort and expense, pecan trees can grow and produce quality nuts for decades. Some commercial pecan plantings in North Carolina are well over 50 years old and still very productive. In years when a full crop is produced, North Carolina produces 5 million to 8 million pounds of pecans; the harvest quantity varies from year to year due to biennial bearing cycles. The magnitude of production ranges from several trees in a backyard to commercial orchards with 30 or more acres. Initial plantings of 50 to 100 trees are common. Whether you own a few trees or a commercial orchard, growing pecans can be a long-term and enjoyable endeavor as well as profitable. As with any venture, however, planning is essential. This publication explains some of the keys to successfully growing pecans.

North Carolina is on the northern fringe of the commercial improved pecan-producing region of the United States. The limiting factor is the length of the growing season. The probability of spring frost damage to early and midseason varieties and the limited selection of late-maturing varieties for North Carolina are limitations on pecan production in the state. North Carolina’s northern fringe location makes proper site and varietal selection crucial for consistent, profitable production. Pecans do not grow well and produce in all parts of the state. The most suitable areas extend from the coastal plain to the eastern edge of the piedmont. Although pecan trees can be grown farther west, nut production may be inconsistent.

The selected site should ideally have 1 to 2 feet of well-drained topsoil with moderate soil-moisture-holding capacity. Pecan trees are native to river valley soils and require a relatively large amount of water. They do best in sandy loam soils but also can be grown on heavier soils such as clay loams if the soils are well-drained. In areas where the soil is lighter and relatively dry, irrigation is required.

To reduce the potential for frost or freeze damage, select a planting site at a higher elevation or on a gradual slope. Do not plant in low areas where cold air tends to settle; these areas are frequently referred to as frost pockets. As cold air settles, the moist air is frequently observed as fog or dew. Orchards planted on a slope also dry more quickly after wet periods, decreasing the wetting period of the orchard and minimizing conditions that favor disease development. Climatological maps can be used to determine potential sites for growing pecans. Information on the length of the season for a particular area, indicated by the number of frost-free growing days and the probability of frost in the spring, is readily available. For information about sites and season length, contact your local N.C. Cooperative Extension center.

A site’s history is a very good indicator of how well pecans will grow. Does the site frequently have frost in late spring or in early fall? Is the site prone to heavy winds from tropical storms and hurricanes, which can devastate pecan orchards due to uprooting and tree damage? Does it have standing water during wet periods, and is water readily available during very dry periods when irrigation is needed? What has been planted on this site in the past several years? Have herbicides or pesticides been used that may still be present in the soil and, if so, will they reduce pecan tree growth when planted? Will drift from pesticides or growth regulators applied to nearby fields harm pecan trees? Are there homes or public areas nearby that might restrict spraying? All of these questions should be addressed before you plant pecan trees.

When selecting a pecan variety, consider pollination requirements, length of growing season, cold tolerance, and scab resistance. Table 1 lists the varieties that have the greatest potential for commercial success in North Carolina. All of the varieties listed have an appropriate growing season and adequate cold hardiness, and they are at least moderately resistant to scab, the primary pecan disease in the state. There is no such thing as a perfect variety, but it is important to understand the characteristics and challenges of the selected varieties and manage accordingly. Pecans have the tendency to alternate or biennial bear—with a large fruit crop followed the next year by a greatly reduced crop—which can be a greater problem in some varieties than others.

Pollination requirements for pecan trees differ from other tree fruit crops. Pecan trees are monoecious, which means that they have separate male and female structures on the same tree: catkins (Figure 1), flowers (Figure 2), and developing nuts (Figure 3). The time at which the male catkins release pollen, however, is not the time at which the female flowers on that plant are receptive to pollination. Pecan trees are separated into two pollination groups referred to as Type I and Type II. Catkins on Type I (protandrous) trees release their pollen before the female flowers are receptive, and catkins on Type II (protogynous) trees release their pollen after the female flowers are receptive. Because of this difference, both Type I and Type II pecan trees are required for pollination. To ensure maximum pollination and production, plant at least three varieties including both Type I and Type II together. Planting even more varieties, due to differences in susceptibility to pecan scab, may help to further minimize the pressure from this disease and associated crop loss.

NOTE: The following common varieties are not recommended for North Carolina because of their cold sensitivity, poor nut quality, low yields, undesirable structural issues, severe alternate bearing, or high pest and disease susceptibility.
Desirable—cold-sensitive; weak tree structure; and moderate to high scab susceptibility.
Mahan—nuts fill poorly; high scab susceptibility; and severe alternate bearer.
Schley—low yielding; high scab susceptibility; and soft shells result in many vertebrate pest-control problems.
Success—variable though frequently poor nut quality; high scab susceptibility; and severe alternate bearer.
Stuart—a historically grown Type II variety in North Carolina for decades but more recently having major issues with marginal nut quality; increased disease sensitivity; and poor filling.

*Scab resistance ranking, from least resistant to most resistant: Poor, Low, Moderate, Good, High ↲

**Very promising resistance to scab but has yet to be proven. ↲

***Alternate-bearing (biennial-bearing) trees are prone to producing a commercial crop only every two to three years. ↲

Figure 1. Catkins (male structures) produce pollen.

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Figure 1. Catkins (male structures) produce pollen.

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Figure 2. Female flowers occur at the tip of the current season’s growth and produce the nuts after pollination.

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Figure 2. Female flowers occur at the tip of the current season’s growth and produce the nuts after pollination.

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Figure 3. Developing nuts form a cluster.

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Figure 3. Developing nuts form a cluster.

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In traditional plantings, when pecan trees are fully mature (about 20 to 25 years after planting), tree spacing should be about 60 to 70 feet between rows and also between trees within rows, resulting in 9 to 12 trees per acre. There are alternative management systems that warrant mentioning here that may be more economical and increase cash flow in pecan plantings during the initial years. Some growers plant pecan trees in fields that are grazed by animals during the growing season. This practice, however, is not recommended for new plantings. Ground covers planted up to the trunk of a pecan tree reduce tree growth due to competition for moisture and nutrients and ultimately delay production; soil around the trees may be compacted by the animals; and large animals frequently damage young pecan trees. The presence of grazing animals may prohibit the use of approved pesticides for pecan trees, resulting in greater than usual losses due to insects and diseases. In addition, research has shown that nuts may be contaminated by bacteria found in the animal waste, posing food safety concerns if not managed properly.

Another option is to plant 6 to 12 pecan trees per acre and then intercrop between the pecan trees with peaches, vegetables, corn, grain, hay, or another crop. The advantage to this system is that it provides cash flow during the pecan orchard’s formative years. A disadvantage, however, is that pecan trees may be damaged by the equipment being used for the intercrop. It can also be easy to ignore the pecan trees as a long-term source of income when looking at the cash flow from the intercrop with a short-term perspective. In addition, materials used in producing the intercrop must be compatible and labeled for use in pecan trees.

Pecan trees can also be initially planted at a high density on 30-foot to 35-foot centers, 36 to 49 trees per acre, to encourage early nut production on a per acre basis, with some of the trees being temporary and some permanent. This system will allow for greater nut production early in the life of the orchard. When the trees start to crowd or shade each other, 12 to 15 years after planting, some of the temporary trees are removed, either by cutting them down or transplanting them with a very large tree spade. The remaining temporary trees are removed 17 to 20 years after planting. For this system to be profitable, careful attention to detail is essential, and the orchard must be established with a well-designed management system. The permanent trees must be identified at planting, making sure that the correct varieties for pollination remain after the trees have been thinned (Figure 4). Also, the temporary trees selected must be precocious varieties (those that bear fruit early). Physically mapping the orchard on paper is the best way to ensure the final stand has the correct permanent trees, and it provides a record for future planning. The temporary trees must be removed as soon as they begin to shade the permanent trees. Resist the temptation to leave the temporary trees in place for that “one more crop,” as this will reduce the ultimate productivity of the permanent trees due to excessive shading. Several rules of thumb for tree thinning are to remove trees when branches of adjacent trees touch; when more than 60% of the orchard floor is shaded during the summer at noon; or when a ring of light cannot be seen around the shade of a pecan tree at noon in mid-June (Figure 5).

Another management option when planting at high density (for example, 30 to 35 feet in both directions) is to use annual hedging to maintain light distribution within the planting. However, this approach requires the use of tree hedging equipment, which can be cost-prohibitive on a limited acreage basis.

Planting

Purchase and plant only healthy trees that have been produced by grafting or budding a commercial variety onto a seedling rootstock. The selected variety on top is called the scion, which is grafted (Figure 6) or budded (Figure 7) onto a pecan rootstock. Using grafted or budded trees will help ensure true-to-type varieties, early production, and high nut quality. Purchase the trees from a reputable nursery. In many cases, the trees are sold as dormant, bare-root trees that must be planted during the dormant season. It is crucial that the tree’s root system does not dry out from between the time trees are received from the nursery and when they are planted in the orchard. Plant the dormant trees in early winter for optimum results. A good tree size at planting is 4 to 6 feet tall. Because pecan trees have a taproot (which can be pruned back at planting), the planting hole should be deep and wide enough to accommodate the root system without curling the roots (for example, a 2-foot-diameter augured hole). See the NC State Extension video "Planting Pecan Trees" for guidelines.

Plant the tree so that the bud or graft union is at least 2 inches above the soil surface after planting and settling. Another general rule is to plant the trees so that the top root from the nursery is at the soil surface. Trees planted too deep do not form necessary surface roots (Figure 8) or a resulting trunk flare at the soil surface. A root flare (Figure 9) enables the tree to stand up to heavy winds. Figure 10 shows an example of a toppled tree that was planted too deep and didn't develop the necessary roots to stabilize it. The planting hole should be filled in with the native soil. Do not add any fertilizer to the hole. Do not apply fertilizers to the soil surface until the soil has settled around the newly planted tree. Water the trees well after planting. Maintaining adequate moisture throughout the first year is essential for tree growth and survival. After planting, the lower 18 to 24 inches of the trunk can be painted with white latex paint to reflect sunlight to minimize injury from freezing temperatures (usually during late winter temperature fluctuations) and to also protect from any herbicide application drift. Observe the trees periodically for damage from insects, borers, rodents, deer, rabbits, and diseases. Take corrective action at the first visible signs of damage.

When planting trees, especially in light, sandy soil, an irrigation system is strongly encouraged. Low-volume lower-pressure systems with micro sprinklers are ideal (Figure 11). Trickle or drip systems are not recommended on light, sandy soil because the movement of the irrigation water by capillary action is low, resulting in primarily downward movement of moisture with little lateral movement. Note that irrigation sprinklers should be placed in a manner that will not impede harvest.

Figure 4. A high-density orchard is gradually being thinned.

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Figure 4. A high-density orchard is gradually being thinned.

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Figure 5. Pecan orchard in June during noontime. Note the light ring around the shade cast by each tree.

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Figure 5. Pecan orchard in June during noontime. Note the light ring around the shade cast by each tree.

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Figure 6. Grafted tree after planting.

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Figure 6. Grafted tree after planting.

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Figure 7. Budded pecan tree after planting.

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Figure 7. Budded pecan tree after planting.

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Figure 8. A pecan tree that is planted too deeply does not form a root flair at the soil surface.

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Figure 8. A pecan tree that is planted too deeply does not form a root flair at the soil surface.

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Figure 9. A pecan tree with a root flare can endure heavy winds.

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Figure 9. A pecan tree with a root flare can endure heavy winds.

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Figure 10. This young pecan tree was planted too deeply, did not form a root flare at the soil surface, and blew over during a moderate wind.

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Figure 10. This young pecan tree was planted too deeply, did not form a root flare at the soil surface, and blew over during a moderate wind.

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Figure 11. A microsprinkler low-volume system emitter provides irrigation.

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Figure 11. A microsprinkler low-volume system emitter provides irrigation.

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The NC State Extension video "Pruning Pecan Trees" provides helpful pruning guidelines. After planting, prune back the top of the tree by about one-third to promote optimal tree structure (Figure 12). The buds close to each pecan branch’s tips are very closely spaced (Figure 13), and the resulting growth results in sharp crotch angles and competing shoots (Figure 14). By cutting off the terminal portion of the tree, the resulting branches will be optimally spaced and allow for the selection of a strong central leader. In addition, pruning will allow for better branch spacing and balance with the root system. During removal in the nursery, shipping, and planting, much of the tree’s root system is damaged.

Pecan trees should be trained to a central leader system (Figure 15). Central leader trees have a main trunk growing straight up, with lateral branches (or scaffolds) from the main trunk spiraled every 16 to 18 inches (Figure 16a). Pecans are different from most fruit trees in that they have at least three vegetative buds at each node as opposed to one (Figure 17). The orientation of the branches from these nodes is very different and is used to guide tree training. Just before the buds begin to grow in the spring, select the topmost or primary bud, which produces a very upright branch, to be the central leader (Figure 16b and Figure 18). All other primary buds on the leader should be removed by horizontally rubbing across the leader without damaging the lower buds, just before budbreak. Secondary and tertiary buds with wider crotch angles can be used for training the lateral branches, as shown in Figure 16b.

Because pecan wood is brittle, only branches with a wide crotch angle (greater than 60 degrees) should be retained; this will minimize future branch breakage along each tree’s central leader trunk (Figure 19). The lower lateral scaffolds should be selected from secondary buds that have a little more of an upright angle. The scaffolds in the top portion of the tree should be selected from tertiary buds having a relatively flatter angle; this will allow more light to penetrate the tree’s lower portion. During the trees' formative years (three to five years), all lateral growth can be retained. However, as the trees mature, all growth on the trunk below 6 feet should be removed for ease of management and nut harvest. These temporary lateral branches should be removed when they are approximately 1 inch in diameter. It is desirable to limit the height of pecan trees to approximately 50 to 60 feet for ease of management. The trees should be pruned to maintain the desired height by pruning to an outward growing lateral branch similar in diameter to the central leader being removed.

Renovating Old Trees

Many pecan plantings in North Carolina have been neglected for years. Renovating trees that are 75 feet or taller is costly and usually not economically feasible. Severe pruning of older trees reduces their productivity for at least three years. The best way to manage these orchards is to thin out and remove the trees as needed to attain proper light penetration and air movement. After thinning the necessary trees, remove any dead, diseased, or damaged branches on the remaining trees. Any branches that are crowded together or that cross over each other also should be removed during the dormant season. If major pruning is planned, it should be done over a period of at least three years to minimize the production decrease and the resulting surge in growth from the pruning cuts, beginning at the top of the tree. Each year, make several large cuts in each tree. Under no circumstances should trees be “dehorned” (significantly cutting back all branches).

Fertilization

Nutrition in pecan orchards should be managed using visual observation, soil analysis, and foliar analysis. For optimal production for bearing trees, the lateral terminal branches should grow about 8 to 10 inches each year. If more or less growth occurs, the fertility program may need to be modified.

Soil samples can be collected and submitted for analysis at the same time as foliar samples. Before planting, take soil samples from two depths within the soil profile: (1) from an 8-inch depth, and (2) from an 8-inch to 16-inch depth. Each sample should be a composite of at least 20 subsamples from across a field with the same soil type. Fields under different management systems or with different soil types should be sampled separately. The samples can be submitted through your local Extension center. For specific instructions on collecting samples, see the NC State Extension publication Careful Soil Sampling — The Key to Reliable Soil Test Information. You will receive a report with recommendations for correcting the soil pH and any nutrient deficiencies. Perform a soil analysis before planting new trees; the soil in the entire planting area should be modified based on soil test recommendations to a depth of at least 16 inches or as deep as possible. Soil pH for pecan trees should be in the range of 6.0 to 6.5. Soil samples can be collected every other year.

Foliar analysis can be analyzed with leaflet samples collected in mid- to late July. The sample should consist of at least 100 leaflets from the middle of the compound leaves on the current season’s growth. Collect leaflets that are not damaged and growing in full sun. To ensure accuracy, do not collect samples after recent pesticide or nutrient spray applications. Place the leaflets in an open paper bag or in perforated paper sample bags to allow them to dry. Then submit the sample through your local Extension center along with a nominal fee for analysis. You will receive a foliar analysis report with recommendations for avoiding or correcting deficiency symptoms.

Although foliar and soil sampling are suggested for determining nutrient needs, a rule of thumb for fertilizing nonbearing trees is to apply 1 pound of 10-10-10 fertilizer (10% nitrogen, 10% phosphorus, and 10% potassium) per year of tree age in late February or early March, not to exceed 25 pounds per tree. For bearing trees, apply 4 pounds of 10-10-10 fertilizer per inch of trunk diameter measured just below the scaffold branches. Broadcast the fertilizer in a broad band around the tree’s drip line. Pecan trees also require adequate zinc, as determined by a soil analysis. Although zinc deficiencies are uncommon in North Carolina, this element should be monitored due to its importance. If zinc deficiency symptoms are documented, apply foliar applications of 1.6 ounces of zinc sulfate in 5 gallons of water after 1 inch of new growth in the spring; repeat every three to four weeks to help correct the deficiency.

Managing the Orchard

Pecan orchards should have grassed row middles and vegetation-free strips down the tree rows (Figure 20). The bare strips are usually maintained with herbicides registered for use on pecans. Broadleaf weeds within the grassed middles can be controlled with selective herbicides to eliminate alternate hosts for pecan pests and aid in harvest management. Cultivation is not recommended because even very shallow cultivation will destroy the trees’ surface roots.

Figure 12. Head or cut back the central leader of pecan trees by approximately one-third at planting.

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Figure 12. Head or cut back the central leader of pecan trees by approximately one-third at planting.

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Figure 13. Terminal buds are closely spaced.

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Figure 13. Terminal buds are closely spaced.

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Figure 14. The growth from an unheaded branch tip, unheaded at planting, needs to be thinned for optimal tree structure.

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Figure 14. The growth from an unheaded branch tip, unheaded at planting, needs to be thinned for optimal tree structure.

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Figure 15. This pecan tree is trained to a central leader.

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Figure 15. This pecan tree is trained to a central leader.

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Figure 16. Proper pruning relies on a pecan tree’s growth habits. a. Optimally trained central leader tree. b. Pecan trees have at least 3 buds at each node. The buds at the top result in branches more upright than lower buds and are used to train trees.

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Figure 16. Proper pruning relies on a pecan tree’s growth habits. a. Optimally trained central leader tree. b. Pecan trees have at least 3 buds at each node. The buds at the top result in branches more upright than lower buds and are used to train trees.

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Figure 17. Multiple buds occur at each node.

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Figure 17. Multiple buds occur at each node.

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Figure 18. Multiple buds occur at each node, each with a different growth habit. Only one branch, at most, is left at each node.

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Figure 18. Multiple buds occur at each node, each with a different growth habit. Only one branch, at most, is left at each node.

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Figure 19. This breakage resulted from a sharp crotch angle that affected the tree’s central leader trunk.

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Figure 19. This breakage resulted from a sharp crotch angle that affected the tree’s central leader trunk.

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Figure 20. Controlling the vegetation in the tree row is necessary. The width of the clean strip depends on many factors, but to the drip-line would be ideal.

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Figure 20. Controlling the vegetation in the tree row is necessary. The width of the clean strip depends on many factors, but to the drip-line would be ideal.

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Pecans are subject to attack by more than 20 insects and mites, but only a few are troublesome enough to be of economic importance in North Carolina. These include pecan weevils, southern green stink bugs (and their relative, the leaf-footed bug), pecan twig girdlers, yellow and black aphids, and ambrosia beetles. It is important to be able to recognize damage caused by these insects and to understand their life history to know when to monitor for their presence and when to control them using integrated pest management (IPM) strategies. For information about IPM, visit NC State Extension's Integrated Pest Management Topic Site.

Pecan Weevil

The pecan weevil is the most serious late-season pest of pecan trees because it affects the nut. Adult pecan weevils are beetles with long, slender snouts and thin legs. Beetles are reddish-brown to gray and 0.3 to 0.5 inches long (Figure 21). The snout is longer than the body on the females and slightly shorter on the males. Eggs are white and are laid inside the developing pecan nuts. Larvae are creamy-white, legless grubs with reddish-brown heads (Figure 21). They have four growth stages and are 0.35 inches long when fully grown. Pupae develop underground and are seldom seen. Adult weevils emerge from the soil from August through September; often a rainfall of 1 inch precedes the initial emergence the first of August. Pecan weevils cause two types of damage (Figure 21). Adults crawl or fly into the tree, depositing eggs into the pecans. Damage at this time causes the nuts to fall while still in the shuck after two or three days. The second type of damage is caused by larval feeding within the nut. At maturity, the larvae chew a small, circular hole through the shell; when nuts fall to the ground, the larvae exit the nut and burrow into the soil, where they can remain for one to two years. They pupate and emerge as adults in about three weeks but remain in the soil for future seasons. Alternative hosts for pecan weevils are hickory trees.

Southern Green Stink Bug and Leaf-Footed Bug

Both the southern green stink bug and the leaf-footed bug can attack pecan nuts, causing similar damage. They puncture nuts both before and after shell hardening (Figure 22). If the insects feed before shell hardening, the nuts fall prematurely. If they feed after shell hardening, black spots develop on the nut kernel. These black spots are bitter and referred to as kernel spot or bitter pit (Figure 22).

The southern green stink bug is large, green, shield-shaped, and about 0.5 inches long. Adults have wings, but nymphs are wingless. The leaf-footed bug has a narrow body and long, leaf-shaped hind legs. Both species overwinter as adults in debris in the orchard. They emerge in the spring and lay eggs in grasses or soybeans and then move to pecans as adults. Both species produce four or five generations per year.

Twig Girdlers

The pecan twig girdler is a large beetle with long antennae (Figure 23). It girdles twigs and small branches in September. Females lay clear, glassy eggs in slits in the girdled branches. These branches fall to the ground when the force of the wind breaks the remainder of the partially severed twig. Larvae feed in the branch and exit to pupate in the soil. Only one generation is produced each year.

Aphids

Two species of aphids affect pecans. Yellow aphids and black aphids feed on the leaves of pecan trees and deposit honeydew, a sweet excrement, on the leaves. A sooty mold fungus develops on the honeydew and turns the surface of the leaves black. Severely damaged leaves may appear speckled or may have patches that turn brown and die. Heavily infected trees exhibit premature leaf fall.

Adult aphids are either yellow or black and have soft bodies with delicate wings and a pair of tubes projecting from the abdomen. Immatures are wingless and usually appear in colonies. Both species overwinter as eggs in bark crevices. Nymphs are active in the spring. Ten or more generations may be produced in a year.

Ambrosia Beetles

Ambrosia beetles must be monitored in young plantings. The first generation emerges in early spring and bores a hole approximately 1/16 inch in size into the tree (Figure 24, upper left), where it deposits eggs and a fungus on which the young feed. The borer also tunnels in the tree (Figure 24, lower left). A toothpick-like pupal casing ultimately emerges from the trunk via the borer hole (Figure 24, right). The primary damage caused by this insect is the introduced fungus, which infects the tree, altering its vascular function and leading to tree collapse and subsequent death. Trees most prone to attack are those under stress. Young trees should be monitored for ambrosia beetles in early spring, and spray applications should begin as soon as possible after holes or pupal casings are observed.

Other Insects

Some other minor insects of concern include casebearers, hickory shuckworms, leafminers, mites, fall webworm, spittlebugs, and phylloxera. For additional help in insect identification and management, contact your local Extension center.

Insect Monitoring

Monitoring in a systematic way provides valuable information on the populations of pests and beneficial insects in an orchard. The results can be used to determine the need for and proper timing of pesticide applications. Two monitoring techniques used in pecan orchards are field surveying and insect trapping. In sampling for foliar insects, randomly select five compound leaves and five nut clusters from five trees in a 10-acre block. Record observations on a weekly basis and refer to these records regularly to make comparisons and identify trends. Marking trees with numbers is helpful in establishing permanent reference points.

Insect traps are used to catch pests, monitor their development, and indicate when additional sampling is required. A black-light insect trap can be used for moths, beetles, and stink bugs. Pheromone traps that contain a sex attractant are available for many insects. These pheromone traps are species-specific. There are two types of traps that monitor for pecan weevils. Cone cage traps with a pheromone in the cone’s peak are placed under the tree’s drip line and record the number of adult weevils collected. Burlap fabric can be wrapped in overlapping flaps around the trunks of several trees in an orchard (Figure 25). Daily collections of male and female weevils indicate when to spray, and destroying the weevils collected provides some physical control.

Figure 21. The pecan weevil punctures nuts, and its larvae damage the kernel and then create a small hole through which the larvae exit the nuts.

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Figure 21. The pecan weevil punctures nuts, and its larvae damage the kernel and then create a small hole through which the larvae exit the nuts.

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Figure 22. The stink bug punctures nuts and damages the meats.

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Figure 22. The stink bug punctures nuts and damages the meats.

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Figure 23. The twig girdler damages small branches.

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Figure 23. The twig girdler damages small branches.

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Figure 24. Ambrosia beetle damage: Hole bored into tree for deposit of eggs and fungus (upper left); tunneling by the borer beneath bark (lower left); toothpick-like pupal casings (right).

Photo by Lenny Wells, University of Georgia

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Figure 24. Ambrosia beetle damage: Hole bored into tree for deposit of eggs and fungus (upper left); tunneling by the borer beneath bark (lower left); toothpick-like pupal casings (right).

Photo by Lenny Wells, University of Georgia

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Figure 25. Pecan weevil monitoring: Burlap is wrapped around trees 3–4 feet above soil and tied in place at bottom. The remaining burlap is overlapped and tied at the top, causing weevils to walk over each flap and allowing time for grower observation.

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Figure 25. Pecan weevil monitoring: Burlap is wrapped around trees 3–4 feet above soil and tied in place at bottom. The remaining burlap is overlapped and tied at the top, causing weevils to walk over each flap and allowing time for grower observation.

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Pests besides insects and mites also may be encountered in a pecan orchard. They include sapsuckers, squirrels, blue jays, crows, and deer. One of the best ways to manage these pests is to locate the orchard at least 200 feet away from wooded areas and eliminate brushy and heavily wooded fencerows. Other specific control strategies are described in the following pest profiles.

Sapsuckers

Sapsuckers are woodpeckers that bore holes in pecan trees, which allows them to access sap to feed on and also attracts insects they consume. This frequently creates a pattern of holes in concentric circles around the trunk and branches (Figure 26). Although unsightly, minor damage of this type is tolerable; however, extensive feeding by these woodpeckers can weaken the brittle pecan wood, making it more susceptible to wind and ice damage. There are no practical ways to control sapsuckers. For smaller orchards, the use of aluminum flashing loosely placed around the tree trunks where the sapsuckers are starting to drill may provide some protection.

Squirrels, Crows, and Blue Jays

Squirrels, crows, and blue jays will enter the orchard and “steal” or destroy nuts (Figure 27). Besides locating the orchard away from wooded areas, the best control method relies on commercial noisemakers, most of which sound like a gun firing. Many different systems are available, but the animals will get used to the noise over time. Other scare materials, such as mylar balloons, mylar tape, and plastic owls and hawks, may provide some wildlife control. Additional control strategies include removing the animals by means of traps or hunting, both of which may require pest-removal or depredation permits. For smaller plantings, squirrels may be deterred by 2-foot-wide strips of sheet metal placed all the way around the pecan tree (be careful not to girdle the tree). It is difficult for squirrels to climb on the slick metal surface. Springs may be used to hold the sheet metal to the tree while allowing flexibility for the tree to expand.

Deer

Deer can cause serious tree damage—both by feeding on the new growth and by rubbing their antlers on younger trees during the fall. Several commercial products can be sprayed on the trees to repel deer, but the materials must be reapplied on a 10- to 12-day schedule. Hanging small bars of perfumed soap (with their wrappers still on), strips of dryer sheets, or bags of human hair or bone meal on individual trees also has proven an effective deterrent in some situations. Removing animals by hunting when the law allows or with a pest-removal (depredation) permit is another option. Deer fencing will be the most effective and most costly deterrent.

Figure 26. Sapsucker injury on pecan trees consists of pecked holes, often in concentric circles.

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Figure 26. Sapsucker injury on pecan trees consists of pecked holes, often in concentric circles.

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Figure 27. Bird and squirrel damage can be a serious issue in many orchards and one very difficult to control.

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Figure 27. Bird and squirrel damage can be a serious issue in many orchards and one very difficult to control.

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Diseases, especially the fungal disease known as pecan scab, are a major hindrance in pecan production. Fungicide programs are designed around the management of scab and adjusted as needed for other diseases. Scab affects both the foliage and fruit. Powdery mildew and anthracnose are other fungal diseases affecting both foliage and fruit but are erratic in occurrence compared to pecan scab. Diseases of foliage include downy spot and bacterial leaf scorch. Phytophthora shuck and kernel rot is a disease of fruit but is erratic in occurrence and limited in distribution. Other diseases are of minor importance or not fully understood; these include bunch disease, crown gall, mistletoe, nematodes, and numerous minor foliar diseases.

Pecan Scab

Pecan scab (Figure 28), caused by the fungus Cladosporium caryigenum, has been a known problem in pecan production since 1888 and is recognized as the most destructive disease of pecan trees. Without fungicide applications, certain cultivars would experience yield losses ranging from 50% to 100%, depending on the year. The severity of scab is mainly influenced by rainfall during the growing season, being more severe during wet years. Pecan scab occurs on leaves, twigs, and nut shucks. All tissues are most susceptible when young and actively growing. Scab causes lesions, which typically begin as small, olivaceous-to-black spots, 1 to 8 millimeters across, with a velvety appearance when the fungus is sporulating. Lesions may coalesce and become large and irregularly shaped. Early nut shuck infections can cause tremendous yield and crop quality reductions; scab infections that develop late in the season on the shuck are less damaging to both yield and quality. Once the shell hardens, subsequent infection is apparently more cosmetic than damaging.

Bacterial Leaf Scorch

Bacterial leaf scorch (BLS) (Figure 29) is caused by Xylella fastidiosa, a xylem-limited bacterium. Marginal scorching of leaves and defoliation first occur on the older leaflets. Although more than 20 cultivars have been found to be susceptible, Cape Fear is generally the cultivar associated with BLS in North Carolina pecan orchards. The pathogen is transmitted by xylem-feeding insects, such as sharpshooter leafhoppers and spittlebugs. Grafting has also been associated with the spread of these organisms. There are no control measures for BLS, although damage can be reduced by cultural practices that reduce stress to the trees (for example, proper irrigation, fertility, and weed management).

Powdery Mildew

Powdery mildew (Figure 30), caused by the fungus Microsphaera penicillata, is of limited importance due to its sporadic occurrence and the lack of significant damage. Powdery mildew infects foliage and fruit, although fruit infection is more common. Infections typically become apparent during July, when plant tissue is covered by a white “powdery” growth that forms the reproductive structures of the pathogen. Powdery mildew can be suppressed with proper fungicide selection.

Downy Spot

Downy spot (Figure 31), caused by the fungus Mycosphaerella caryigena, is a foliar disease of pecan. The initial symptom of downy spot is a faint, circular spot on the underside of leaflets. The spots are between 2 and 5 millimeters wide and may appear whitish and “fuzzy” due to sporulation of the pathogen. Over time, the lesion turns from whitish to yellowish. The lesions develop upward through the leaf blade and about six to eight weeks later become visible on the upper leaf surface as yellowish spots with indistinct margins. Severely infected leaflets may begin dropping later in the season. Downy spot is not typically a problem in orchards that are well-managed for scab, as the fungicides used on scab also control downy spot.

Anthracnose

Anthracnose (Figure 32), caused by the fungus Glomerella cingulata, is a disease of both foliage and fruit. The pathogen is widespread throughout the Southeast, although the occurrence of anthracnose is erratic from year to year. Foliar lesions typically develop on foliage in late summer. Lesions are dark-brown and irregular, usually starting along the margin of leaflets. A distinct, dark margin exists between the necrotic and healthy tissue. Lesions on the shuck are dark and sunken, occurring along sutures in the shuck, near the proximal end, or at wounds where nuts are attached. Stress factors such as heavy crop load, overcrowding, drought, and insect pressure have been associated with more severe disease development. Fungicides used for control of scab are thought to be effective for control of anthracnose also.

Chemical Control of Pecan Pests

Losses from disease can be prevented only with a carefully planned spray program. All fungicides currently available for pecan disease control must be used in a preventive manner, as they have little effect on existing infections. Pesticides should be applied with an orchard air-blast sprayer to provide adequate coverage over the entire tree (Figure 33). Fungicides must be applied regularly to maintain a protective barrier over the foliage and fruit. The standard disease prevention program calls for applications at 10- to 14-day intervals from budbreak until pollination and 14- to 21-day intervals from pollination until shell hardening. This schedule will need to be adjusted depending on factors including season, varieties, and orchard history. Most growers modify the standard program to best meet individual needs and pest pressure.

The pecan weevil, the most serious pest in North Carolina, can be controlled with foliar insecticide sprays during August. Weevil emergence, as determined by trap catches, will identify critical periods for pesticide application.

Recommendations for controlling insect and disease issues can be found in the University of Georgia's Commercial Pecan Spray Guide, which is updated annually. You can also contact your local N.C. Cooperative Extension center for help identifying pests and for recommended control measures.

Nonchemical Control of Pecan Diseases

Although fungicides remain the main consideration for management of pecan diseases, other factors should not be ignored. When cultural and environmental factors are improved, the efficacy of fungicides can also improve. Cultivar resistance and cultural practices, including proper cultivar selection, site selection, tree spacing, pruning, orchard thinning, fertility, and irrigation, can all play a role in overall tree health and disease development.

• Do not allow orchards to become overcrowded. Pruning or tree removal can help avoid overcrowding, making water use more efficient, improving sunlight exposure, improving air movement, and potentially diminishing damage from many diseases such as pecan scab. In overcrowded orchards, leaves will remain wet longer, which provides favorable conditions for disease development. Inadequate fungicide coverage is also a complication associated with overcrowded orchards.

• Select suitable cultivars. Planting disease-resistant cultivars is the most economical and practical control measure, especially for scab. Breeding program ratings are available from state universities and the United States Department of Agriculture, but keep in mind that performance will vary by location. Avoid overreliance on two or three cultivars because cultivar susceptibility to scab is likely to change over time and planting multiple cultivars is key to achieving successful cross-pollination.

• Manage fertility. Plant nutrition affects both the growth and development of the tree and contributes to the tree’s natural defense against pathogens and disease development. Several relationships between the levels of particular nutrients and susceptibility to diseases have been discovered. Macronutrients (including nitrogen, potassium, and phosphorus) and micronutrients (including boron, nickel, molybdenum, and zinc) are both important in plant health and may play a role in the plant’s defense mechanisms against pathogens. Recent studies have provided evidence that healthy trees are more tolerant of pathogens. Although attention to macronutrient or micronutrient levels will not eliminate disease, optimal nutrition during the development of foliage and fruit may greatly improve the chances for genetic resistance within the tree. See the “Fertilization” section.

• Maintain sanitary conditions. Remove all dead and infected material from the orchard. Manage weeds, promote optimal growth and light penetration, and control invertebrate pests.

Figure 28. Pecan scab occurs on the petioles, leaves, and developing nuts.

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Figure 28. Pecan scab occurs on the petioles, leaves, and developing nuts.

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Figure 29. Bacterial leaf scorch affects pecan leaflets.

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Figure 29. Bacterial leaf scorch affects pecan leaflets.

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Figure 30. Powdery mildew affects foliage and pecans.

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Figure 30. Powdery mildew affects foliage and pecans.

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Figure 31. Downy spot occurs on pecan leaflets.

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Figure 31. Downy spot occurs on pecan leaflets.

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Figure 32. Anthracnose occurs on pecan foliage and developing nuts.

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Figure 32. Anthracnose occurs on pecan foliage and developing nuts.

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Figure 33. Air-blast orchard sprayers are most effective at managing insect and disease pressure and are available from various manufacturers in many different models and sizes.

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Figure 33. Air-blast orchard sprayers are most effective at managing insect and disease pressure and are available from various manufacturers in many different models and sizes.

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Pecans are harvested when the shuck opens, allowing the nuts to drop (Figure 34). Mechanical aids can be used to help speed nut fall once the shucks are open. These devices range from a long pole used to shake small limbs to large commercial branch or trunk shakers that cause nuts to fall in a very short time (Figure 35). In small-scale operations, sheets can be spread under the tree to catch the falling nuts. Nuts also can be picked up with small, hand-operated harvesters; larger push-propelled harvesters ranging from 12 to 48 inches wide for small-scale plantings; or large commercial mechanical nut harvesters (Figure 36). Nuts harvested by hand should be picked up every other day to prevent the nuts from molding or being destroyed or removed by pests.

Once harvested, the nuts must be dried to 6% to 8% moisture for short-term storage or 3.5% to 4.5% moisture for freezing and long-term storage. For small-scale production, the nuts can be dried by placing them in burlap or porous produce bags in a location with moderate ventilation and heat. For larger volumes, commercial dryers use forced air heated to about 100°F for optimal drying.

Like all nuts, pecans have a relatively high oil content and will become rancid and spoil under poor postharvest conditions. For optimal storage, they can be held at 32°F for about one year. For longer storage periods, the nuts should be kept in a freezer.

If pecans are sold in the shell, the price is determined by the market, variety, nut size, percentage shell-out, presence of shell damage, and whether any of the shuck is still adhering to the shell. If the pecans are sold shelled, the price is usually determined by the kernel color, shell fill, presence or absence of insect damage, percentage of mold, and size. Pecan cracking devices (Figure 37) are used to crack the shells, which then must be removed or separated from the nuts with a sheller. One problem that commonly reduces the price of nuts is the presence of a fuzzy "packing" material on the kernel. It can be removed by the consumer using a brush or toothpick between the ridges. Packing material is a result of the nut being stressed during the growing season, often by inadequate moisture. The only way to prevent this problem is by suitable variety selection and preventing any stress disorders in the tree all season long.

Figure 34. These pecans are ready for harvest.

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Figure 34. These pecans are ready for harvest.

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Figure 35. Shakers for removing nuts from the tree when mature are available in many different sizes for various sized trees and orchards.

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Figure 35. Shakers for removing nuts from the tree when mature are available in many different sizes for various sized trees and orchards.

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Figure 36. Harvesters that collect the nuts from the orchard floor are available in many different sizes.

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Figure 36. Harvesters that collect the nuts from the orchard floor are available in many different sizes.

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Figure 37. Pecan cracking devices crack the shells, which must be separated from the nuts.

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Figure 37. Pecan cracking devices crack the shells, which must be separated from the nuts.

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NC State Extension Horticulture Topic Site. "Comprehensive Resources for Fruit Trees."

NC State Extension. 2017. "Successfully Growing Pecans in North Carolina." Instructional video.

North Carolina State University College of Agriculture and Life Sciences. North Carolina Agricultural Chemicals Manual (AG-1). Revised annually. NC State Extension.

Wells, Lenny (Ed.). 2024. Southeastern Pecan Growers' Handbook. University of Georgia Extension.

Wells, Lenny (Ed.). Commercial Pecan Spray Guide. Updated annually. University of Georgia Extension.