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Pecan Nut

•
•
M
MANDEEP KAUR

This document provides an overview of pecan production technology. It begins with an introduction to pecans, describing their importance and nutritional value. It then discusses pecan varieties, production practices such as propagation, spacing, pruning, and fertilization. Health benefits and nutritional content of pecans are highlighted. Details are given on pecan tree description, floral biology, fruit description, and ecological requirements. Major pecan producing countries and varieties are identified. Common pecan diseases and their management are also summarized.

1 of 43
Pecan Nut Production Technology Mandeep Kaur Ph.D. Fruit Science
Introduction & Importance • Pecan is derived from an Algonquian word, meaning a nut requiring a stone to crack. • Pecan (Carya illinoinensis, 2n=32) is the most economically important member of the Carya genus, belongs to family Juglandaceae & is native to North America. • In the USA, pecan is considered the queen of nuts because of its value both as a wild & as a cultivated nut & acceptable quality of nutrients (Woodroof 1979). • Pecan has highly valued edible, sweet & flavoured nuts. • Nuts can be consumed after being cooked or roasted, mostly used in a large number of processed products i.e. candies, chocolates, ice-cream, baked goods etc. • Nut oil is used in soap & perfume products. • Pecan wood is used for furniture, cabinetry & paneling.
Health Benefits of Pecans • Pecans are great defense against many modern ailments, like lowering high cholesterol & reversing type II diabetes & gallstones in women. • Research proves eating about a handful of pecans (1.5 ounces) each day could have a similar effect as cholesterol lowering medications. • A great antioxidant & high in unsaturated fats, pecans also help to curb appetites. Nutritional value of per 100 g of nuts Energy 691 Kcal Carbohydrates 13.86 g Protein 9.17 g Total fat 71.9 g Cholesterol 0 mg Dietary fiber 9.6 g Vitamin A 56 IU Vitamin E 24.44 mg Potassium 410 mg Calcium 70 mg Magnesium 121 mg Phosphorus 277 mg Zinc 4.53 mg Iron 2.53 mg
World Pecan Production Kernel Basis (Metric Tons) Global pecan production showed an increasing trend over the last 10 years, adding up to over 124,000 metric tons (kernel basis) in the 2017-2018 season.
World Pecan Production In 2017-18 Kernel Basis (Metric Tons) • About 92% of pecans were produced in North America. • The USA and Mexico accounted for 51% and 41% of the world production, respectively. • In a smaller range of production, South Africa and Australia produced the remaining 8%. *Source: https://www.nutfruit.org/files/tech/1524481168_INC_Statistical_Yearbook_2017-2018.pdf
World Pecan Exports In 2016 Shelled (Metric Tons) • Mexico and USA accounted for 62% and 36% of the 2016 world exports, respectively. • The majority of Mexican exports were related to the USA. • The main importers from the USA were Canada (25% of the country share), the Netherlands (18%), the UK (11%) and China (10%).
Pecan Nut Tree Description • Pecan trees are moderate to tall growing, (20-40 m), deciduous, monoecious with dark coloured, hard wood & deep tap roots, crown open, spreading at the top, bark thick with prominent lenticels. • A 10-year-old sapling grown in optimal conditions will stand about 5 m (16 ft) tall. • Branches with solid pith & erect to slightly spreading. • The leaves are alternate & 30–45 cm long
Floral Biology • Flowering of Carya species is complex. • Mature pecan trees bear staminate (male) & pistillate (female) flowers at different locations on the same tree (monoecy). • Staminate & pistillate flowers mature at different times on an individual tree (dichogamy). • Heterodichogamy in pecan populations encourages genetic diversity by maximizing outcrossing. • Dichogamy in pecan is under single gene control, with protogyny being dominant (Thompson & Romberg 1985).
Staminate flower • Male flower (catkins) appears on previous season growth laterally. • Many catkins are produced from a single bud. • Each staminate flower occur in cluster of three, light green measures about 4-6 inches in length, with 5-6 stamens. Pistillate flower • Female flower appear in few to several flowered cluster, terminally on current season growth. • Each pistillate flower consists of a small yellow pubescent, 4 angled or lobed involucre enclosing single celled ovary & stigma finely divided.
Fruit Description • Fruit, oblong to globular, broad at base, pointed at apex, clustered in groups of 3- 6, husk thin & narrow, 4 winged & 4 angled. • Husk splits along wing or suture to expose the nut. • Nuts, oblong to cylinder shaped, broader at base, apex short pointed, brown to reddish brown with few black spots on the thin soft smooth shell. • Kernel is sweet with more oil content.
Ecological Requirements Climate • Pecans grows in a humid climate & requires the minimum average annual rainfall of 760 mm. • Mean summer temperature range as high as 27 ͦC, & can tolerate an extremes of 41 ͦC to 46 ͦC. • Average winter temperatures vary from 10 ͦC to -1 ͦC, with extremes of -18 ͦC to -29 ͦC (Putnam 1951, Adams and Thielges 1977). Soils & Topography • Pecan grows commonly on well drained loamy soils, which are not subjected to prolonged water logging. • It rarely grows on low & poorly clays, where it is replaced by water hickory (Carya aquatic) (Adams and Thielges 1977, Nelson 1965).
Important Species • The Genus Carya has 20 species & except 4, all are native to the Americas. • Pecan is only species which is important commercially while other species like C. ovata, C. laciniosa & C. cordiformis also produce kernel which are sweet in taste, but being thick shelled are poor in cracking quality. • C. ovata: Flavor & quality highest among native hickory nuts. Nuts are small, whitish distinctly 4 angular, thin shelled hull thick, opens to the base, shell has longitudinal ridges. • C. laciniosa: Nuts yellowish white, four angled does not open along suture lines, kernel not well filled, sweet in taste. • C. cordiformis: Shell & hull thin, kernel poor in quality due to astringency & bitterness. • C. tomenstose: Hull thick splits to the base, nuts pear shaped thick shelled, sweet & edible, difficult to shell out as halves. • C. glabra: Nut small, shell & hull thin.
Important Commercial Varieties Early pollen shedding varieties (Protoandrous varieties) Desirable Western Pawanee Caddo Cheyenne Cape Fear Late pollen shedding varieties (Protogynous varieties) Wichita Forket Maramec Mohawk Shoshoni Sioux
Taylor Carman Kennedy Hodge Bolto n San Saba Centennial Jewett Frotscher Padst Moneymaker Hollis Success Schley Young
Pecan Nut
Pecan Nut Production in India • In India, Pecan was introduced in 1935. • It is grown in Jammu & Kashmir, Himachal Pradesh, Uttaranchal & Nilgiri Hills. • Jammu & Kashmir & Himachal are principal pecan producing states in India. • Despite many constraints, agro-climatic conditions of Jammu & Kashmir are ideally suited to pecan growth & production. • In Himachal Pradesh, pecan plantations remain confined to Kangra, Mandi, Kullu & Solan districts, which constitute approximately 700 ha.
Propagation Method • Patch or ring budding may be used to propagate nursery stock or top work larger pecan trees. • Scion wood should selected before the buds begin to swell. • Budding may be done as late as June or July. • However, earlier buds will have more time to produce a stronger union with the rootstock & will produce more vegetative growth during the 1st year. • Budding can also be done in late July & August using matured wood from the current year’s growth without storing; however, this is often a less successful method. • Protect all wounds & strips from the sunlight & wind. • The best time to plant pecan tree is December - January.
Size, chilling requirements and other characteristics of seeds of pecan species used as rootstocks Species Seed weight (g) Chilling requirement (days) Optimal Chilling temp. ( ͦC) Speed of germination (days) Seed viability (years) Carya illinoensis (Pecan) 0.1-0.4 30-90 5 20 1-3 Carya aquatic (Water hickory) 0.4 90-150 1 - - * Source : USDA (1974) and USDA (1961)
Pecan Rootstocks • Pecans do not root easily from cuttings, so seedling pecans are used as rootstocks. • Riverside seedlings are commonly used in Texas, while seedlings of Elliott & Curtis are popular in southern United States. • Seedling of Carya aquatic (hickory) have been used for wet soils, but the nuts of pecan are usually smaller when grown on hickory, than when grown on pecan rootstocks. • With recent improvement in clonal propagation, pecan selections are being made for dwarfing & for nutrient uptake, particularly for chloride exclusion and zinc enhancement (Hanna 1987).
Spacing • Pecans develop into a large trees, growing to 20-40 m in height, rarely to 44 m, with massive root systems. • So, trees should be planted at distance of 8-10 m. • Trees planted too close develop poor health, have unattractive shapes. When crowding occurs, nut production & quality becomes poor.
Flowering Kind Flower initiation Flowers borne on Season of anthesis relative to season of initiation Male flower Early summer Lateral buds, 1 year old shoots Next spring Female flower Early spring Terminals of current shoots Same season • Pecan is monoecious plant i.e. staminate and pistillate flowers are born separately on the same tree. • Being anemophilous, pollination is done by wind. • Flowers have no petals & consist of large reflexed stigmas attached to an ovary.
Variety Percent kernel No. of nuts/kg Pollen shedding Stigma receptivity Maturity Desirable 56 110 Early Late M Elliott 43 172 Late Early M Ideal 56 143 Late Early M San Saba 60 - Early Late E Success 52 110 Early Late M Stuart 49 116 Early Late M Monarch 27 143 - - - Characteristics of some Pecan varieties • The pecan is largely self fertile but dichogamous, & with some varieties there is no overlap of pollen shedding & stigma receptivity. • Most varieties require at least 180 days & up to perhaps 220 days, for nuts to mature.
Growth & Development Stages of Pecan Nut • Phase I (Growth in Nut Size): It takes about 90 days after pollination for the fruit to grow to its full size, slowly at first and then more rapidly. Toward the end of August, the fruit has reached maximum size. The endosperm is entirely non cellular until the end of phase I, which is known as water stage. • Phase II (Nut Filling): It occurs from the shell hardening (or end of water stage) until husk splits. The kernel develops and fills out during this phase, ending when the hull splits along the sutures.
Training & Pruning • Training and pruning is essential to get proper shape and size. • Generally, Central leader system is followed in Pecan. • The lowest branch should be kept at 1 m height from the ground level, where as other branches should be placed spirally at distance of 30 cm from one above another. • Light pruning should be carried out on mature trees. • Heavy pruning is not recommended in Pecan as it results in vegetative growth which cause low production. • Only diseased and dead wood branches should be removed.
Fertilization Macronutrients (%) Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg) Sulphur (S) 2.5—3.0 0.14—0.19 1.2—2.5 0.9—1.8 0.3—0.6 0.15—0.35 Micronutrients (ppm or mg per kg) Zinc (Zn) Manganese (Mn) Iron (Fe) Copper (Cu) Boron (B) Nickel (Ni) Chlorine (Cl) 50—100 100—300 50—250 8—30 50—150 >2.5 N/A "Adequate“ Concentration Range of Macronutrients and Micronutrients Recommended for Leaf Tissue of Pecan Trees Sampled in Late July to Early August.
Water Requirement • Pecan trees require more water as compare to other nut trees. • Proper irrigation helps in production of better quality nuts and improves kernel yield, net weight, size and oil content. • Pecan trees can be irrigated through basin system, sprinkler and drip irrigation. Intercropping • Pecan trees come into bearing late, so intercrops like cow pea, soybean, tomato, peas, pulses, beans and any low growing fruit crops can be grown. • The cover crops improves the soil nitrogen level and prevent soil erosion. Weed control • Mulching in the basin of the tree with dry grass should be done to control the weeds and to conserve the soil moisture. • Pre-emergence herbicide i.e. Simazine (3-5 kg/ha) should be used to control the weeds. • Paraquat @ 1 kg/ha can be applied as contact herbicide.
Harvesting & General Storage • Harvesting starts in 1st week of November when husk split to open & separated from nuts. • Mature nuts do not fall, all at once, so mechanical shakers are used to bring them down. • In-shell nuts are alive, their respiration and metabolic activity is much lower at low moisture content of the dried nuts. • Pecans have a high oil content (60-70%) and thus subject to rancidity during storage. The rancidity of unshelled nuts can be detected after 4 months at 21 ͦ C and 2 years at 1 ͦC. • Storage at 75-80% RH and 3.5-6% moisture content is best. • Relative storage life of pecans held at various temperatures are given below. Temperature In-shell (Months) Shelled (Months) 70°F 4 3 47–50°F 9 6 32–36°F 18 12 20–25°F 20–40 18–24 0°F 24–60 24–60
Pecan Nut Harvesting
Pecan Nut Processing
Important Diseases & their Management
Powdery mildew Fungal pathogen Microsphaera penicillata Area(s) affected Nuts and leaves Symptoms A white powdery growth develops on infected nut husk and leaves. Control Powdery mildew typically does not cause significant damage to pecan trees; therefore, treatment for the disease is unnecessary. Affected fruits, leaves & russet appearance on pecan nuts from infection by powdery mildew. *Source: https://aces.nmsu.edu/aes/
Crown Gall Bacterial pathogen Agrobacterium tumefaciens Area(s) affected Trunk and roots Symptoms Woody tumors or galls form on the base of the trunk and root tissue. If the gall girdles the trunk or main roots, the tree may be killed. Control There are no practical management options for plants infected with crown gall. Growers should inspect nursery stock carefully upon arrival and reject any plants with suspicious knots or galls. Crown gall on pecan nut roots & trunk.
Nematodes Nematode Damage potential Pecan root-knot (Meloidogyne partityla) High Lesion (Pratylenchus spp.) Low Stunt (Tylenchorhynchus spp.) Very low Ring (Mesocriconema spp.) Low Spiral (Helicotylenchus spp.) Very low • Galls on pecan roots caused by root-knot nematode. • Dieback and tree decline caused by root-knot nematode.
Scab Fungal pathogen Cladosporium caryigenum Area(s) affected Leaves, nuts and green twigs Symptoms Small, circular, olive-green to black spots form on the lower surface of the leaf and nuts. Control Pecan scab can also be managed using cultural practices such as thinning and pruning. • Early Scab Infection on Pecan Foliage. • Advanced scab infection on pecan leaf. • Severe scab infection on pecan husks .
Pecan Bacterial Leaf Scorch (BLS) Fungal pathogen Xylella fastidiosa, Phomopsis sp., and Glomerella cingulata Area(s) affected Leaves Symptoms Brown to tan dead spots form, on the margin or at the tip of the leaf. A distinct dark brown line separates the dead tissue from the living tissue. Eventually, the whole leaf will turn brown and die. Premature defoliation will occur. Tree affected with Pecan bacterial leaf scorch.
Physiological disorder Alternate bearing • Severe alternate bearing is observed in pecans. • Pecans fruit matures late in the growing season leaving little time prior to leaf fall, for carbohydrates storage to support the next season’s developing flowers & fruit. • Most of the dry matter of the nut accumulate at the end of the season. • Kernels contain about 70% of lipids, which require considerable energy to produce. • These traits, when combined with a heavy fruit set, can leave trees depleted of carbohydrate reserves, especially in the roots, at the end of the season & contribute to poor fruit-set the following year.
Important Insect-pest & their management
Pecan weevil (Curculio caryae) Symptoms Control measures Time of Application • The most serious damage caused by weevil larvae, when it feeds on developing kernel. • Damaged nuts can often be recognized by circular emergence holes, through which the grubs exits the nuts. • Sevin 80 S at 0.6 to 0.7 kg/acre. • Mustang Max at 60 to 70 ml/acre. • Treatment applications should begin about the time, nuts enter the dough stage (around August 20th). • The first treatment should be made following rain because this loosens the soil allowing for weevil emergence.
Black Pecan Aphid (Melanocallis caryaefoliae) Symptoms Control measures Time of Application • The black pecan aphid feeds on both sides of pecan leaflets, causing yellowing and necrosis of areas between the lateral leaflet veins. • It’s damage is usually noticed first on the lowest limbs in the interior portion of the tree. • Provado 1.6 F at 250 to 300 ml/acre. • Admire 2 F at 300 to 500 ml/acre as a soil application. • Treatment is done, when there is an average of one black pecan aphid per compound leaf. • Sample ten leaves on five to ten trees throughout the orchard.
Pecan Nut Casebearer (Acrobasis nuxvorella) Symptoms Control measures Time of Application • In the spring, young larvae feed on developing buds and bore into young developing fruit. • Newly hatched larvae feed on buds and newly set nuts. • Imidan 70 W at 0.5 to 0.9 kg/acre. • Confirm 2 F at 200 to 400 ml/acre. • Insecticide applications should be made, when egg lay is observed on 1 to 3 % of the nut clusters.
Hickory Shuckworm (Cydia caryana) Symptoms Control measures Time of Application • Larvae makes tunnel into nuts before shell hardening, results into dropping. • Entrance holes can often be detected by a white stain around the hole. Lorsban 4 E at 45 to 60 ml/acre. • Spray should done during half-shell hardening (August 10-15). • Two to three applications may be needed at 10 to 14 days interval.
Pecan Phylloxeras (Phylloxera devastatrix) Symptoms Control measures Time of Application • Hard swellings or galls on succulent leaf leaflets or growing terminals. • Severe infestations may produce partial defoliation of affected trees and may interfere with photosynthesis. • Warrior at 75 to 150 ml/acre. • Between the time, the buds begin to open and approximately ½ to ¾ inch of new growth begins to appear.
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Pecan Nut

  • 1. Pecan Nut Production Technology Mandeep Kaur Ph.D. Fruit Science
  • 2. Introduction & Importance • Pecan is derived from an Algonquian word, meaning a nut requiring a stone to crack. • Pecan (Carya illinoinensis, 2n=32) is the most economically important member of the Carya genus, belongs to family Juglandaceae & is native to North America. • In the USA, pecan is considered the queen of nuts because of its value both as a wild & as a cultivated nut & acceptable quality of nutrients (Woodroof 1979). • Pecan has highly valued edible, sweet & flavoured nuts. • Nuts can be consumed after being cooked or roasted, mostly used in a large number of processed products i.e. candies, chocolates, ice-cream, baked goods etc. • Nut oil is used in soap & perfume products. • Pecan wood is used for furniture, cabinetry & paneling.
  • 3. Health Benefits of Pecans • Pecans are great defense against many modern ailments, like lowering high cholesterol & reversing type II diabetes & gallstones in women. • Research proves eating about a handful of pecans (1.5 ounces) each day could have a similar effect as cholesterol lowering medications. • A great antioxidant & high in unsaturated fats, pecans also help to curb appetites. Nutritional value of per 100 g of nuts Energy 691 Kcal Carbohydrates 13.86 g Protein 9.17 g Total fat 71.9 g Cholesterol 0 mg Dietary fiber 9.6 g Vitamin A 56 IU Vitamin E 24.44 mg Potassium 410 mg Calcium 70 mg Magnesium 121 mg Phosphorus 277 mg Zinc 4.53 mg Iron 2.53 mg
  • 4. World Pecan Production Kernel Basis (Metric Tons) Global pecan production showed an increasing trend over the last 10 years, adding up to over 124,000 metric tons (kernel basis) in the 2017-2018 season.
  • 5. World Pecan Production In 2017-18 Kernel Basis (Metric Tons) • About 92% of pecans were produced in North America. • The USA and Mexico accounted for 51% and 41% of the world production, respectively. • In a smaller range of production, South Africa and Australia produced the remaining 8%. *Source: https://www.nutfruit.org/files/tech/1524481168_INC_Statistical_Yearbook_2017-2018.pdf
  • 6. World Pecan Exports In 2016 Shelled (Metric Tons) • Mexico and USA accounted for 62% and 36% of the 2016 world exports, respectively. • The majority of Mexican exports were related to the USA. • The main importers from the USA were Canada (25% of the country share), the Netherlands (18%), the UK (11%) and China (10%).
  • 7. Pecan Nut Tree Description • Pecan trees are moderate to tall growing, (20-40 m), deciduous, monoecious with dark coloured, hard wood & deep tap roots, crown open, spreading at the top, bark thick with prominent lenticels. • A 10-year-old sapling grown in optimal conditions will stand about 5 m (16 ft) tall. • Branches with solid pith & erect to slightly spreading. • The leaves are alternate & 30–45 cm long
  • 8. Floral Biology • Flowering of Carya species is complex. • Mature pecan trees bear staminate (male) & pistillate (female) flowers at different locations on the same tree (monoecy). • Staminate & pistillate flowers mature at different times on an individual tree (dichogamy). • Heterodichogamy in pecan populations encourages genetic diversity by maximizing outcrossing. • Dichogamy in pecan is under single gene control, with protogyny being dominant (Thompson & Romberg 1985).
  • 9. Staminate flower • Male flower (catkins) appears on previous season growth laterally. • Many catkins are produced from a single bud. • Each staminate flower occur in cluster of three, light green measures about 4-6 inches in length, with 5-6 stamens. Pistillate flower • Female flower appear in few to several flowered cluster, terminally on current season growth. • Each pistillate flower consists of a small yellow pubescent, 4 angled or lobed involucre enclosing single celled ovary & stigma finely divided.
  • 10. Fruit Description • Fruit, oblong to globular, broad at base, pointed at apex, clustered in groups of 3- 6, husk thin & narrow, 4 winged & 4 angled. • Husk splits along wing or suture to expose the nut. • Nuts, oblong to cylinder shaped, broader at base, apex short pointed, brown to reddish brown with few black spots on the thin soft smooth shell. • Kernel is sweet with more oil content.
  • 11. Ecological Requirements Climate • Pecans grows in a humid climate & requires the minimum average annual rainfall of 760 mm. • Mean summer temperature range as high as 27 ͦC, & can tolerate an extremes of 41 ͦC to 46 ͦC. • Average winter temperatures vary from 10 ͦC to -1 ͦC, with extremes of -18 ͦC to -29 ͦC (Putnam 1951, Adams and Thielges 1977). Soils & Topography • Pecan grows commonly on well drained loamy soils, which are not subjected to prolonged water logging. • It rarely grows on low & poorly clays, where it is replaced by water hickory (Carya aquatic) (Adams and Thielges 1977, Nelson 1965).
  • 12. Important Species • The Genus Carya has 20 species & except 4, all are native to the Americas. • Pecan is only species which is important commercially while other species like C. ovata, C. laciniosa & C. cordiformis also produce kernel which are sweet in taste, but being thick shelled are poor in cracking quality. • C. ovata: Flavor & quality highest among native hickory nuts. Nuts are small, whitish distinctly 4 angular, thin shelled hull thick, opens to the base, shell has longitudinal ridges. • C. laciniosa: Nuts yellowish white, four angled does not open along suture lines, kernel not well filled, sweet in taste. • C. cordiformis: Shell & hull thin, kernel poor in quality due to astringency & bitterness. • C. tomenstose: Hull thick splits to the base, nuts pear shaped thick shelled, sweet & edible, difficult to shell out as halves. • C. glabra: Nut small, shell & hull thin.
  • 13. Important Commercial Varieties Early pollen shedding varieties (Protoandrous varieties) Desirable Western Pawanee Caddo Cheyenne Cape Fear Late pollen shedding varieties (Protogynous varieties) Wichita Forket Maramec Mohawk Shoshoni Sioux
  • 16. Pecan Nut Production in India • In India, Pecan was introduced in 1935. • It is grown in Jammu & Kashmir, Himachal Pradesh, Uttaranchal & Nilgiri Hills. • Jammu & Kashmir & Himachal are principal pecan producing states in India. • Despite many constraints, agro-climatic conditions of Jammu & Kashmir are ideally suited to pecan growth & production. • In Himachal Pradesh, pecan plantations remain confined to Kangra, Mandi, Kullu & Solan districts, which constitute approximately 700 ha.
  • 17. Propagation Method • Patch or ring budding may be used to propagate nursery stock or top work larger pecan trees. • Scion wood should selected before the buds begin to swell. • Budding may be done as late as June or July. • However, earlier buds will have more time to produce a stronger union with the rootstock & will produce more vegetative growth during the 1st year. • Budding can also be done in late July & August using matured wood from the current year’s growth without storing; however, this is often a less successful method. • Protect all wounds & strips from the sunlight & wind. • The best time to plant pecan tree is December - January.
  • 18. Size, chilling requirements and other characteristics of seeds of pecan species used as rootstocks Species Seed weight (g) Chilling requirement (days) Optimal Chilling temp. ( ͦC) Speed of germination (days) Seed viability (years) Carya illinoensis (Pecan) 0.1-0.4 30-90 5 20 1-3 Carya aquatic (Water hickory) 0.4 90-150 1 - - * Source : USDA (1974) and USDA (1961)
  • 19. Pecan Rootstocks • Pecans do not root easily from cuttings, so seedling pecans are used as rootstocks. • Riverside seedlings are commonly used in Texas, while seedlings of Elliott & Curtis are popular in southern United States. • Seedling of Carya aquatic (hickory) have been used for wet soils, but the nuts of pecan are usually smaller when grown on hickory, than when grown on pecan rootstocks. • With recent improvement in clonal propagation, pecan selections are being made for dwarfing & for nutrient uptake, particularly for chloride exclusion and zinc enhancement (Hanna 1987).
  • 20. Spacing • Pecans develop into a large trees, growing to 20-40 m in height, rarely to 44 m, with massive root systems. • So, trees should be planted at distance of 8-10 m. • Trees planted too close develop poor health, have unattractive shapes. When crowding occurs, nut production & quality becomes poor.
  • 21. Flowering Kind Flower initiation Flowers borne on Season of anthesis relative to season of initiation Male flower Early summer Lateral buds, 1 year old shoots Next spring Female flower Early spring Terminals of current shoots Same season • Pecan is monoecious plant i.e. staminate and pistillate flowers are born separately on the same tree. • Being anemophilous, pollination is done by wind. • Flowers have no petals & consist of large reflexed stigmas attached to an ovary.
  • 22. Variety Percent kernel No. of nuts/kg Pollen shedding Stigma receptivity Maturity Desirable 56 110 Early Late M Elliott 43 172 Late Early M Ideal 56 143 Late Early M San Saba 60 - Early Late E Success 52 110 Early Late M Stuart 49 116 Early Late M Monarch 27 143 - - - Characteristics of some Pecan varieties • The pecan is largely self fertile but dichogamous, & with some varieties there is no overlap of pollen shedding & stigma receptivity. • Most varieties require at least 180 days & up to perhaps 220 days, for nuts to mature.
  • 23. Growth & Development Stages of Pecan Nut • Phase I (Growth in Nut Size): It takes about 90 days after pollination for the fruit to grow to its full size, slowly at first and then more rapidly. Toward the end of August, the fruit has reached maximum size. The endosperm is entirely non cellular until the end of phase I, which is known as water stage. • Phase II (Nut Filling): It occurs from the shell hardening (or end of water stage) until husk splits. The kernel develops and fills out during this phase, ending when the hull splits along the sutures.
  • 24. Training & Pruning • Training and pruning is essential to get proper shape and size. • Generally, Central leader system is followed in Pecan. • The lowest branch should be kept at 1 m height from the ground level, where as other branches should be placed spirally at distance of 30 cm from one above another. • Light pruning should be carried out on mature trees. • Heavy pruning is not recommended in Pecan as it results in vegetative growth which cause low production. • Only diseased and dead wood branches should be removed.
  • 25. Fertilization Macronutrients (%) Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg) Sulphur (S) 2.5—3.0 0.14—0.19 1.2—2.5 0.9—1.8 0.3—0.6 0.15—0.35 Micronutrients (ppm or mg per kg) Zinc (Zn) Manganese (Mn) Iron (Fe) Copper (Cu) Boron (B) Nickel (Ni) Chlorine (Cl) 50—100 100—300 50—250 8—30 50—150 >2.5 N/A "Adequate“ Concentration Range of Macronutrients and Micronutrients Recommended for Leaf Tissue of Pecan Trees Sampled in Late July to Early August.
  • 26. Water Requirement • Pecan trees require more water as compare to other nut trees. • Proper irrigation helps in production of better quality nuts and improves kernel yield, net weight, size and oil content. • Pecan trees can be irrigated through basin system, sprinkler and drip irrigation. Intercropping • Pecan trees come into bearing late, so intercrops like cow pea, soybean, tomato, peas, pulses, beans and any low growing fruit crops can be grown. • The cover crops improves the soil nitrogen level and prevent soil erosion. Weed control • Mulching in the basin of the tree with dry grass should be done to control the weeds and to conserve the soil moisture. • Pre-emergence herbicide i.e. Simazine (3-5 kg/ha) should be used to control the weeds. • Paraquat @ 1 kg/ha can be applied as contact herbicide.
  • 27. Harvesting & General Storage • Harvesting starts in 1st week of November when husk split to open & separated from nuts. • Mature nuts do not fall, all at once, so mechanical shakers are used to bring them down. • In-shell nuts are alive, their respiration and metabolic activity is much lower at low moisture content of the dried nuts. • Pecans have a high oil content (60-70%) and thus subject to rancidity during storage. The rancidity of unshelled nuts can be detected after 4 months at 21 ͦ C and 2 years at 1 ͦC. • Storage at 75-80% RH and 3.5-6% moisture content is best. • Relative storage life of pecans held at various temperatures are given below. Temperature In-shell (Months) Shelled (Months) 70°F 4 3 47–50°F 9 6 32–36°F 18 12 20–25°F 20–40 18–24 0°F 24–60 24–60
  • 31. Powdery mildew Fungal pathogen Microsphaera penicillata Area(s) affected Nuts and leaves Symptoms A white powdery growth develops on infected nut husk and leaves. Control Powdery mildew typically does not cause significant damage to pecan trees; therefore, treatment for the disease is unnecessary. Affected fruits, leaves & russet appearance on pecan nuts from infection by powdery mildew. *Source: https://aces.nmsu.edu/aes/
  • 32. Crown Gall Bacterial pathogen Agrobacterium tumefaciens Area(s) affected Trunk and roots Symptoms Woody tumors or galls form on the base of the trunk and root tissue. If the gall girdles the trunk or main roots, the tree may be killed. Control There are no practical management options for plants infected with crown gall. Growers should inspect nursery stock carefully upon arrival and reject any plants with suspicious knots or galls. Crown gall on pecan nut roots & trunk.
  • 33. Nematodes Nematode Damage potential Pecan root-knot (Meloidogyne partityla) High Lesion (Pratylenchus spp.) Low Stunt (Tylenchorhynchus spp.) Very low Ring (Mesocriconema spp.) Low Spiral (Helicotylenchus spp.) Very low • Galls on pecan roots caused by root-knot nematode. • Dieback and tree decline caused by root-knot nematode.
  • 34. Scab Fungal pathogen Cladosporium caryigenum Area(s) affected Leaves, nuts and green twigs Symptoms Small, circular, olive-green to black spots form on the lower surface of the leaf and nuts. Control Pecan scab can also be managed using cultural practices such as thinning and pruning. • Early Scab Infection on Pecan Foliage. • Advanced scab infection on pecan leaf. • Severe scab infection on pecan husks .
  • 35. Pecan Bacterial Leaf Scorch (BLS) Fungal pathogen Xylella fastidiosa, Phomopsis sp., and Glomerella cingulata Area(s) affected Leaves Symptoms Brown to tan dead spots form, on the margin or at the tip of the leaf. A distinct dark brown line separates the dead tissue from the living tissue. Eventually, the whole leaf will turn brown and die. Premature defoliation will occur. Tree affected with Pecan bacterial leaf scorch.
  • 36. Physiological disorder Alternate bearing • Severe alternate bearing is observed in pecans. • Pecans fruit matures late in the growing season leaving little time prior to leaf fall, for carbohydrates storage to support the next season’s developing flowers & fruit. • Most of the dry matter of the nut accumulate at the end of the season. • Kernels contain about 70% of lipids, which require considerable energy to produce. • These traits, when combined with a heavy fruit set, can leave trees depleted of carbohydrate reserves, especially in the roots, at the end of the season & contribute to poor fruit-set the following year.
  • 38. Pecan weevil (Curculio caryae) Symptoms Control measures Time of Application • The most serious damage caused by weevil larvae, when it feeds on developing kernel. • Damaged nuts can often be recognized by circular emergence holes, through which the grubs exits the nuts. • Sevin 80 S at 0.6 to 0.7 kg/acre. • Mustang Max at 60 to 70 ml/acre. • Treatment applications should begin about the time, nuts enter the dough stage (around August 20th). • The first treatment should be made following rain because this loosens the soil allowing for weevil emergence.
  • 39. Black Pecan Aphid (Melanocallis caryaefoliae) Symptoms Control measures Time of Application • The black pecan aphid feeds on both sides of pecan leaflets, causing yellowing and necrosis of areas between the lateral leaflet veins. • It’s damage is usually noticed first on the lowest limbs in the interior portion of the tree. • Provado 1.6 F at 250 to 300 ml/acre. • Admire 2 F at 300 to 500 ml/acre as a soil application. • Treatment is done, when there is an average of one black pecan aphid per compound leaf. • Sample ten leaves on five to ten trees throughout the orchard.
  • 40. Pecan Nut Casebearer (Acrobasis nuxvorella) Symptoms Control measures Time of Application • In the spring, young larvae feed on developing buds and bore into young developing fruit. • Newly hatched larvae feed on buds and newly set nuts. • Imidan 70 W at 0.5 to 0.9 kg/acre. • Confirm 2 F at 200 to 400 ml/acre. • Insecticide applications should be made, when egg lay is observed on 1 to 3 % of the nut clusters.
  • 41. Hickory Shuckworm (Cydia caryana) Symptoms Control measures Time of Application • Larvae makes tunnel into nuts before shell hardening, results into dropping. • Entrance holes can often be detected by a white stain around the hole. Lorsban 4 E at 45 to 60 ml/acre. • Spray should done during half-shell hardening (August 10-15). • Two to three applications may be needed at 10 to 14 days interval.
  • 42. Pecan Phylloxeras (Phylloxera devastatrix) Symptoms Control measures Time of Application • Hard swellings or galls on succulent leaf leaflets or growing terminals. • Severe infestations may produce partial defoliation of affected trees and may interfere with photosynthesis. • Warrior at 75 to 150 ml/acre. • Between the time, the buds begin to open and approximately ½ to ¾ inch of new growth begins to appear.