For many generations, pecans have been grown on family homesteads in North Carolina as part of a means for survival. Today, pecans are still grown in North Carolina, for income and enjoyment, predominately in the southeastern part of the state. Growing pecans requires patience and a long-term commitment. However, pecan trees can grow and produce quality nuts for decades with minimal effort and expense. Some commercial pecan plantings in North Carolina are well over 75 years old and still very productive. In years when a full crop is obtained, North Carolina produces 5 to 6 million pounds of pecans annually. The level of production ranges from several trees in the backyard to commercial orchards with 20 acres or more. Holdings of 20 to 30 trees are common. Whether you own a few trees or a commercial orchard, growing pecans can be enjoyable as well as profitable. However, as with any venture, planning is essential. This document will explain how to produce pecans successfully.
Managing Pests and Diseases
North Carolina is on the northern fringe of the commercial 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 mid-season varieties and the limited selection of late-maturing varieties for North Carolina are both limitations of pecan production. North Carolinas' northern-fringe location makes proper site and varietal selection crucial for consistent, profitable production.
Pecans do not grow well in all areas of the state. The best area is the coastal plain, extending to the eastern edge of the piedmont. Although pecan trees can be grown further west, nut production is limited because of inconsistent cropping.
The selected site should have well-drained, deep soils (4 to 6 feet) with moderate soil-moisture-holding capacity. Pecan trees are native to river valley soils and have a relatively high water requirement. They do best on 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 site at a higher elevation or one 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 seen 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 diseases. 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 help, contact your county Cooperative Extension Center.
Knowing the history of the site is also a very good indicator of how well pecans will grow. Does the site frequently have frost in late spring or in early fall? Does it have standing water during wet periods, and is water readily available during very dry periods if irrigation is needed? What has been planted on this site in the last several years? Have herbicides or pesticides been used that may still be present in the soil? If so, will they reduce pecan tree growth when planted? Are pesticides or growth regulators applied to nearby fields that may harm pecan trees? Are homes or public areas nearby that might restrict spraying? All of these questions should be answered 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.
|Variety||Size (Nuts/lb)||Percent Kernel||Scab Resistance (years)||Fruit Bearing Age||Comments|
|T Y P E I|
|Cape Fear||55||55||Moderate||5 to 7||A native North Carolina variety.|
|Pawnee||54||55||Moderate to Low||6 to 7||New USDA release, may be greatly affected by aphids.|
|T Y P E I I|
|Stuart||48||48||Moderate||8 to 10||Major variety grown in North Carolina, high, consistent yields on mature trees.|
|Sumner||55||52||High to Moderate||5 to 6||Late maturing, consistent cropper.|
|Forkert||53||62||Moderate to Low||5 to 6||Thin-shell variety.|
|Chickasaw||64||55||Moderate||5 to 6||Kernels may be dark, severe alternate bearer.*|
|Elliott||71||53||High||7 to 9||May be aphid-susceptible, older trees may alternate bear.|
|Kiowa||46||56||Moderate||5 to 6||May alternate bear.|
|Gloria Grande||48||48||High||7 to 9||Very cold tolerant.|
Pollination requirements for pecan trees differ from all other tree fruit crops. Pecan trees are monoecious, which means that they have separate male structures, called catkins, and female flowers on the same tree. However, the time at which the male catkins release pollen is not the time at which the female flowers can be pollinated. Pecan trees are separated into two pollination groups referred to as Type I and Type II. Catkins on Type I trees release their pollen before the female flowers are receptive and catkins on Type II 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 therefore, production, at least three varieties should be planted together.
When pecan trees are fully mature, approximately 20 years after planting, tree spacing should be approximately 70 to 80 feet between rows and also between trees within rows, or six to nine trees per acre. However, alternative management systems that may be more economical and increase cash flow on pecan plantings during the initial years will be discussed in this publication. Pecan trees have commonly been planted in fields that are grazed by animals during the growing season. However, this practice is not recommended with newer plantings. Several problems occur with this system: ground covers planted up to the trunk of the pecan tree reduce tree growth and promote insect problems, soil around the trees may be compacted by the animals, and large animals frequently damage young pecan trees. With grazing animals present, proper pesticides usually are not applied, resulting in greater insect and disease losses. Also, research has shown that nuts may be contaminated by bacteria found in the animals' manure, causing those who eat the nuts to become ill.
Another system is to plant six to nine pecan trees per acre and then intercrop between the pecan trees with peaches, corn, or grain. The advantage to this system is that it provides cash flow during the formative years of the pecan orchard. However, a disadvantage is that pecan trees may be neglected or damaged by the equipment being used for the intercrop. It is also easy to ignore the pecan trees as a long-term source of income when looking at the cash flow from the intercrop on a short-term perspective.
Pecan trees can also be planted initially on 30- to 35-foot centers, 36 to 49 trees per acre, with some of the trees being temporary and some permanent. 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. Again, at 17 to 20 years after planting, the remaining temporary trees are removed. 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 before planting, making sure that the correct varieties for pollination remain after the trees have been thinned. Also, the temporary trees selected must be precocious varieties(those that bear fruit early) such as Cape Fear, Kiowa, Sumner, Chickasaw, or Forkert.
It is very important to remove the temporary trees as soon as they begin to shade the permanent trees. It is often tempting to leave the temporary trees in for that "one more crop," thereby reducing the ultimate productivity of the permanent trees because of excessive shading. Two rules of thumb for tree thinning are to remove trees when branches of adjacent trees touch or when more than 60 percent of the orchard floor is shaded during the summer at noon.
Purchase and plant only healthy trees that have been produced by grafting a commercial variety onto a seedling rootstock. Using grafted trees will help ensure early production and high nut quality. Purchase the trees from a reputable nursery, usually as bare-root trees. A good size is 4 to 6 feet tall. Plant the trees in late fall or early winter for optimum results. Because pecan trees have a tap root, the planting hole should be deep and wide enough for the root system without curling the roots. Plant the tree so that the graft union is 2 inches above the soil surface after planting. The planting hole should be filled in with the native soil. Do not add any fertilizer to the tree 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. Observe the trees periodically for damage from insects, borers, rodents, deer, rabbits, and diseases. Take corrective action at the first visible signs of damage.
After planting, cut back the top vegetative portion of the tree approximately one-third to maintain balance with the root system. During shipping and planting much of the tree's root system is damaged or removed.
Pecan trees should be trained to a central leader system. Central leader trees have a main trunk growing straight up with lateral branches, or scaffolds, from the main trunk spiraled every 8 to 16 inches (Figure 1a). Pecans are different from most fruit trees in that they have at least three buds at each node. The orientation of the branches from these nodes is very different and is used for tree training. Just before the buds begin to grow in the spring, buds can be selected to train the tree to a central leader form. The primary bud is the top bud and produces a very upright branch, which should be the central leader (Figure 1b). All other primary buds should be removed by rubbing them off just before bud break. Secondary and tertiary buds can be used for training the lateral branches, as shown in Figure 1b.
Because pecan wood is brittle, only branches with a wide crotch angle (greater than 60 degrees) should be selected. The lower 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, beginning in approximately the third year, should be selected from tertiary buds having a flat angle (80 to 85 degrees) to allow more light to penetrate the lower portion of the tree. It is essential to limit the height of pecan trees to approximately 40 feet for ease of management. The trees should be topped at the desired height by cutting to an outward growing lateral branch similar in diameter to the central leader being removed. It also is important to maintain a single central leader for optimal productivity and growth.
Many pecan plantings in North Carolina have been neglected for years. Renovating 75-foot-tall trees is costly and usually not economically feasible. Drastic pruning on older trees reduces their productivity for at least three years. This loss can never be recovered. The best way to manage these orchards is to thin out the trees as needed to attain proper light penetration. After removing the necessary trees, remove any dead, diseased, or damaged branches on the remaining trees. Any branches that are crowding and that cross within the trees 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. Each year make several large cuts in each tree to minimize the production decrease and the resulting surge in growth from the pruning cuts.
Nutrition in pecan orchards should be managed using visual observation, soil analysis, and foliar analysis. Pecan trees should grow at least 8 to 10 inches on terminal branches each year for optimal production. If more or less growth occurs, the fertility program may need to be modified.
Soil samples should be collected and submitted for analysis at the same time each year. Samples should be taken from the soil surface to an 8-inch depth and from the 8- 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 different soil types should be sampled separately. The samples can be submitted through your local Cooperative Extension Center. (For information on collecting samples, see Cooperative Extension Service Publication AG-439-30, Careful Soil Sampling.) You will receive a report in the mail with recommendations for correcting the soil pH and any nutrient deficiencies. A soil analysis should be obtained before planting new trees, and the soil should be amended as necessary to a depth of at least 16 inches. Soil pH for pecan trees should be in the range of 6.0 to 6.5.
Foliar analysis can be determined 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 those that are 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 sample bags to allow them to dry. Then submit the sample through your county Cooperative Extension Center along with a nominal fee for analysis. You will receive a foliar analysis report through the mail with recommendations for avoiding or correcting deficiency symptoms.
A rule of thumb for fertilizing nonbearing trees is to apply 1 pound of 10-10-10 fertilizer (10 percent Nitrogen, 10 percent Phosphorus, and 10 percent 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 drip line of the tree. Pecan trees also require adequate zinc as determined by a soil analysis. If zinc deficiency symptoms are seen, foliar applications of 1.6 ounces of zinc sulfate in 5 gallons of water applied after 1 inch of new growth in the spring and repeated every 3 to 4 weeks will help correct the deficiency.
Pecan orchards should have grassed row middles and vegetation-free strips down the tree rows. The bare strips are usually maintained with herbicides. Broadleaf weeds within the grass middles can be controlled with selective herbicides to eliminate alternate hosts for pecan pests. Cultivation is not recommended because even very shallow cultivation will destroy the trees' surface roots.
Irrigation is also strongly encouraged to maximize pecan production. Low-volume irrigation systems, such as drip or micro-sprinkler systems have been very effective at maintaining tree growth and productivity.
Pecans are subject to attack by more than 20 insects and mites. However, only four insects, the pecan weevil, twig girdler, stink bug, and aphids, are usually of economic importance in North Carolina. 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 control them using Integrated Pest Management (IPM) strategies.
The pecan weevil is the most serious late-season pest because it attacks the nut. Pecan weevils cause two types of damage (Figure 2). In the first type, weevils puncture the nuts in early August, causing the nuts to fall after two or three days. The second type is caused by larval feeding within the nut. At larval maturity, the larva chews a circular hole through the shell, and, as nuts fall to the ground, it exits the nut, and burrows into the soil.
Adult pecan weevils are beetles with long slender snouts and thin legs. Beetles are reddish brown to gray and 0.3 to 0.5 inch long. 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 2). They have four stages and are 0.35 inch 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 their emergence. Adults crawl or fly, mate, and live for many days. Females chew holes into nuts where they lay eggs. At maturity the larvae exit the nut and burrow into the soil where they remain for one to two years. They pupate and emerge as adults in about three weeks and remain in the soil until the following August. Alternative hosts for pecan weevils are hickory trees.
Both southern green stink bugs and leaf-footed bugs attack pecan nuts. They puncture nuts both before and after shell hardening (Figure 3). If they feed before shell hardening, the nuts fall prematurely. If the feeding occurs after shell hardening, then black spots develop on the nut kernel. These black spots are bitter and referred to as kernel spot or bitter pit (Figure 3).
The southern green stink bug is large, green, shield-shaped, and about 0.5 inch 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 of five generations per year.
The pecan twig girdler is a large beetle with long antennae (Figure 4). 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.
Two species of aphids affect pecans. Yellow and black aphids feed on the leaves of pecan trees and deposit honeydew, a sweet excrement, on the leaves. A black 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 pro-jecting 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 a year.
Some other minor insects of concern include casebearers, leafminers, mites, fall webworms, spittlebugs, hickory shuckworm, and phylloxeras. For further help in insect identification and management, contact your county Cooperative Extension Center.
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 time pesticide applications properly. 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 containing a sex attractant also are available for many insects. These pheromone traps are very species specific. There are two ways to monitor for pecan weevils using traps. The first is to place cone cage traps under the tree's drip line and record the number of adult weevils collected. A second way is to use trunk band traps. Burlap bags can be wrapped in overlapping flaps around the trunks of several trees in an orchard. Daily collections of male and female weevils indicate when to spray, and destroying the weevils collected provides some physical control (Figure 5).
Another method of monitoring pests is to place a sheet of plastic or cloth on the ground under the trees. Shake the trees and count the insects on the sheet. Trees also can be sprayed with a commercial pesticide and then checked later for the number and species of insects found on the sheet. In the case of twig girdlers, fallen twigs can be examined for the smooth, cut surface caused by adult beetles. The best management strategy for these insects is sanitation by removing and burying or burning these twigs as soon as they fall from the tree.
Recommendations for controlling insects can be found in the North Carolina Agricultural Chemicals Manual and in Sources of Additional Information. You also can contact your county Cooperative Extension Center for help in identifying pests and for recommended control measures. 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.
Some other pest management strategies include:
In North Carolina the major disease of concern is pecan scab. It is caused by a fungus that attacks both the leaves and the shuck. This disease, which infects only immature leaves, primarily occurs early in the season and is identified by small circular spots that range in color from olive to black. These spots enlarge, causing the leaf to be smaller and deformed, which reduces the photosynthetic potential of the tree. Lesions on the nut shucks appear as small sunken black spots and in severe cases may turn the entire shuck black. Severely affected shucks will fall prematurely, and later infections may cause the shucks not to release properly from the nut.
Pecan scab is managed primarily by selecting resistant varieties and by applying a fungicide early in the season. Refer to your county Cooperative Extension Center for fungicide recommendations.
As mentioned in the insect section, sooty mold is a fungus that feeds on the sweet excrement of aphids. This secondary fungus covers the leaf surface as a black chalk and can limit the productivity of the leaves if it is heavy enough to limit their photosynthetic potential. This fungus can be managed by controlling the aphid populations in the tree.
Other pests 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 as follows.
Sapsuckers are birds, similar to woodpeckers, that peck holes in a ring pattern and frequently in concentric circles on the trunk and large branches of trees. They peck holes into the tree so that insects will be attracted to the sap oozing from the holes. The sapsuckers then return at a later time to feed on these insects. Although unsightly, minor damage of this type is tolerable. Extensive sapsucker feeding can weaken the brittle pecan wood, resulting in greater wind and ice damage. There are no effective ways to control this pest. For smaller orchards the use of aluminum flashing loosely placed around the tree trunks where the sapsuckers are starting to drill can provide some protection.
Squirrels, crows, and blue jays will enter the orchard and "steal" nuts. Aside from locating the orchard away from wooded areas, the best control method is the commercial noise makers, most of which sound like a gun firing. Many different systems are available; however, the animals will get used to the noise with time. Other scare materials, such as mylar balloons 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 require pest removal permits. Squirrels may be controlled by placing 2-foot-wide strips of sheet metal all the way around the pecan tree, being careful not to girdle the tree. Springs may be used to hold the sheet metal to the tree while allowing flexibility for the tree to expand.
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 applied on a 10- to 12-day schedule. Hanging small bars of perfumed soap (with their wrappers still on), bags of human hair, or bone meal from individual trees also has proven effective in some situations. Again, removing animals by hunting when the law allows or with a pest removal permit are other options.
Once harvested, the nuts must to be dried to 8 to 10 percent moisture, or to 3.5 to 4.5 percent for optimal long-term storage. For small-scale production, the nuts can be dried by placing them in porous burlap bags in a location with moderate ventilation and heat. Commercial dryers use forced air heated to approximately 100°F for optimal drying.
Pecans, like any nut, have a relatively high oil content and will spoil. For optimal storage, they can be held at 32°F for approximately 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 variety, nut size, 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 percentage shell out, kernel color, development, insect damage, percentage of mold, and size. One problem that commonly reduces the price of nuts is the presence of a fuzzy material on the kernel. This material is a result of the nut being stressed during the growing season, often by inadequate moisture. The only way to avoid this problem is by allowing tree growth to proceed season long without any stress disorders.
Pecan Production in the Southeast; A Guide for Growers. $33.00, Head, Information Services, Alabama Cooperative Extension Service, Auburn University, AL 36849-5623
North Carolina Agricultural Chemicals Manual. Revised annually. $12.00, Publications Office, North Carolina State University, Campus Box 7603, Raleigh, NC 27695-7603
Epperson, D. L. et al. Weather and Climate in North Carolina. AG-375, North Carolina State University, 48 pp. *
Johnson, G. L. and K. M. Williams. Risk of Frost and Freeze Damage for North Carolina Fruit Crops. AG-403, North Carolina State University, 15 pp. *
Johnson, G. L. and K. M. Williams. Low-Temperature Probability Data for North Carolina . AG-403S, North Carolina State University, 91 pp. *
Sorensen, K. Pecan Insects and their Management in North Carolina. 1994. Entomology Insect Note, P-2, 5 pages. *
Sorensen, K. Insects and Related Pests of Pecan. 1987. Entomology Insect Note, P-1, 4 pages. *
*Contact your county Cooperative Extension Center for copies of these publications.
Illustration: Nickola Dudley