Crop Profile for Pecans in Arkansas

Prepared: February 2003

General Production Information

Production Regions:
Commercial pecan production in Arkansas is primarily located on alluvial soils near most major rivers in central, eastern, and southern Arkansas. Significant production areas are found along the Arkansas, Mississippi, Red, and St. Francis rivers.

Production Methods:
Pecans are produced from native (seedling trees) or from orchards of improved (clonally-propagated) varieties. Most pecans produced in Arkansas come from native groves that have been improved and are managed with few inputs. Improvement of native groves generally involves removal of competing trees and shrubs; thinning of pecan trees to retain trees with highest production, best nut quality and highest disease resistance; establishment of permanent ground cover under trees (cool season grasses and legumes) and fertilization.

Native pecan acreage is often grazed by cattle and this presents challenges for the use of pesticides. Most acreage of native pecans is harvested mechanically although significant production is hand harvested by small growers.

Improved pecan varieties are grown in orchards with management to control diseases, insect pests, and weeds. Drip irrigation is used in some planted orchards. Improved pecan orchards are harvested mechanically. Yield is higher and more consistent for improved varieties and nut quality is higher. However, production inputs and management intensity are also higher for improved varieties as compared to native varieties.

Commodity Destination(s):
Pecans are sold in-shell through local retail outlets and to pecan processors who sell shelled pecans through various market channels. The distribution of Arkansas pecan production between these methods of marketing is unknown.



Cultural Practices

Worker Activities

Occasional pruning (approximately 10% of pecan acres) of pecan trees is performed in the dormant season.

Preemergent herbicide applications are applied in early spring, primarily with tractor mounted spray equipment. Postemergence herbicide applications are made in early summer and occasionally after harvest primarily with tractor mounted sprayers although backpack sprayers are occasionally used. Row middles are mowed during the growing season.

Insecticides and fungicides are applied from early spring up to harvest primarily with orchard blast sprayers. A small percentage of the pecan acreage is treated with fungicides and insecticides via aerial application.

Harvest is primarily by hand pick-up although mechanical tree shakers (followed by hand harvesting) are utilized by a majority of growers.



Insect Pests

Pecan Nut Casebearer
Acrobasis nuxvorella

This gray moth is nocturnal and the most damaging insect pests of pecan in Arkansas. Eggs are laid on the tip end of the nutlets. Females will lay 50-150 eggs during their 5-8 day life span. The eggs are white when laid, but turn pink to red prior to hatching. These eggs will hatch in 4-5 days. The green caterpillars grow up to 13mm in length and feed in the developing nuts. Silk webbing with conspicuous dark colored frass eliminated by the larvae is usually seen holding the infested nuts together at their base. Even one larvae is capable of destroying all the nuts in a cluster. Warm spring temperatures influence Casebearer development. Cool, rainy weather can delay moth activity and egg laying. The period of egg laying can vary as much as two weeks from year to year. The second-generation larvae also attack the nuts but the damage is less severe. Later generations feed on the foliage or in the green shuck, causing very little damage. These insects have from one to four generations per year. By carefully monitoring egg hatch and with good control of the first and second generation, the third and fourth generations will be controlled. The first generation is the most damaging.

Control: Scout for eggs and larvae when the tips of the nuts turn brown after pollination, inspecting 200 nut clusters. Insecticide control should be applied 2-3 days after the first eggs hatch or when you find 1-3% nut cluster damage. The following compounds are registered for pecan nut casebearer control: Ammo, Asana, Endosulfan, Imidan, Lorsban, Malathion, Neemix, Phaser, Sevin and Thiodan.


Hickory Shuckworm
Cydia caryana or Laspeyresia caryana

These are brown-headed, dirty white caterpillars. They can be up to 13mm long as mature larva. They feed internally in the immature nuts and cause them to drop. After shell hardening they feed inside the green shucks which prevents proper kernel development.

This insect is most active at night, and overwinters as a larva in the shucks of nuts. It begins attacking nuts in early-June and continues until harvest. In newly dropped nuts, you can often detect a chalky, white deposit at the larval entry point. This deposit is the scales of the female moth, placed to protect and seal the egg to the shuck. The larva will create a paper thin "window" in the shuck prior to pupation, which protects the pupa and provides an easily torn exit hole. Shuckworms have 3-4 generations per year. Emergence of the shuckworm varies from year to year and orchard to orchard depending on the temperature. The adult moths are dark-gray with a one-half inch wingspan.

Control: Activity should be monitored with use of two black-light traps per orchard. Check the light traps three times a week looking for adult moths. In the absence of black-light traps, start scouting for activity in July using pheromone traps. The following compounds are registered for hickory shuckworm control: Ammo, Asana, Imidan, Lorsban, Neemix and Sevin.


Pecan Phylloxeras:
Pecan Stem Phylloxera
Phylloxera devastatrix Pergande
Pecan Leaf Phylloxera
Phylloxera russelae Pergande
Pecan Phylloxera
Phylloxera notabilis Pergande

There are several species of phylloxera that attack pecan, leaf phylloxera, stem phylloxera and pecan phylloxera. These are very tiny greenish-yellow aphid-like insects contained in galls, abnormal swellings, on the leaves or stems. Stem infestations can weaken the shoots that will cause shoot death. Leaf infestations are not severe or damaging to a mature tree but can contribute to premature defoliation. Pecan stem phylloxera is the most important type of phylloxera that can infest pecan. Stem phylloxera produces galls where the nut clusters would normally develop. Phylloxera overwinter in the egg stage in protected places on the tree. There are several generations per year as long as there is new growth on the tree.

Control: Inspect pecan trees for phylloxera in May. Mark the trees that have galls on them for treatment the following year. Dormant oil may be applied to trees before budbreak in late-February to early-March. Insecticides may be applied after eggs hatch in the spring but before nymphs are protected inside the galls. This is usually after budbreak when leaves are 1-2 inches long. The following compounds are registered for control of pecan leaf phylloxera: Asana, Endosulfan, Lorsban, Malathion, Neemix, Phaser, Provado, Sevin, Temik and Thiodan.


Pecan Leaf Scorch Mite
Eotetranychus hicoriae McGregor

These mites are about 0.2mm in size. They are long and pale green in color. They feed primarily along the midribs and veins on the underside of the leaves. This feeding causes a scorch appearance on the foliage. Infestations usually begin in the lower portions of the tree and move upward. In some instances, almost complete defoliation will occur. Damage occurs in June through September and appears as dark brown blotches on the leaflets. These mites overwinter in bark crevices on the tree limbs. Their life cycle is usually 11-15 days.

Control: The following compounds are registered for control of pecan leaf scorch mite: Lorsban, Pyramite, Savey and Vendex.


Pecan Weevil
Curculio caryae Horn

Adults are a brownish-gray in color and about 13 mm in size. They attack pecans and hickory prior to shell hardening causing the nuts to drop. Nuts in the water stage, if fed on by this weevil, will drop prematurely. Damaged nuts usually have a pinhole puncture surrounded by a dark moist stain. After the water stage, but during the jell stage, females chew a hole through the shell and deposit eggs inside the nut. Larvae hatch and feed in the nut for several weeks destroying the kernels. Mature larva have a brown head, are creamy white and legless. They leave the nut to drop down and pupate in the soil. A complete life cycle requires 2-3 years.

Control: The following compounds are registered for control of pecan weevil: Ammo, Asana, Imidan, Neemix and Sevin.


Nut Curculio
Conotrachelus nicoriae (Schoof)

The dark gray to reddish-brown adults are 5mm long. They have a slightly curved snout that is approximately one third their body length. The larvae are small, legless creamy white grubs and are found inside the nut. Adults attack the immature nut with their snouts. Females make shallow crescent shaped punctures with their snout then deposit an egg. Eggs hatch within 4-5 days. These adult punctures are very visible and cause sap bleeding that resembles a tobacco stain. This feeding will cause premature nut drop. Adults overwinter in the ground trash and other protected places. This is an occasional minor pest. There is one generation per year.

Control: This pest is usually controlled by pecan nut casebearer sprays. There is no registered control compound labeled for this pest.


Yellow Aphids Complex:
Black-Margined Aphid
Monellia caryella
Yellow Pecan Aphid Monelliopsis pecanis

Both the yellow pecan aphid and black-margined aphid are similar in appearance and cause similar types of damage. These aphids are very small (1.5mm) and green-yellow in color. Yellow pecan aphids have red eyes and long setae that tend to stand out from the body at 45 to nearly 90-degree angles giving them a pincushion look. The black margined-aphid has much shorter setae that are less than a 45-degree angle with the body. Both species have multiple generations per year. They both feed on the under surface of the leaves. The yellow hickory aphids feed on the network of small veins located throughout the leaf while the black-margined aphids feed on the underside of leaves on the major leaflet veins. They secret honeydew which promotes black sooty mold growth. Both the honeydew and mold coating the leaf surface will interfere with photosynthesis efficiency. Fire ants have been known to protect these aphids from their natural enemies.

Control: The following compounds are registered for control of yellow pecan aphids: Admire, Ammo, Asana, Ammo, Lannate, Lorsban, Malathion, Provado, Pyramite and Temik.


Black Pecan Aphid
Melanocallis caryaefoliae

These aphids are dark-green to black-green in color. They are very small, about 1.2mm in length. They feed on top and bottom surfaces of the leaflets causing bright yellow areas that later turn brown and die. These aphids can be serious pests of pecan. They cause premature leaf drop and contribute to defoliation of the tree.

Control: The following compounds are registered for control of black pecan aphid: Admire, Ammo, Asana, Endosulfan, Imidan, Lannate, Lorsban, Malathion, Phaser, Provado, Temik and Thiodan.


Stink Bugs and other True Bugs:
Southern Green Stinkbug
Nezara viridula, Leptoglossus spp., Euchistus spp. and others

These are green and brown, shield-shaped bugs which are 13-38mm in length. They have piercing-sucking mouthparts and a triangular shape between the base of the wings. Adults feed on immature nuts causing the interior to darken and premature drop from the tree. Feeding after shell hardening causes brown to black pithy bitter spots on the kernels which will reduce nut quality.

Control: Imidan is registered for control of stinkbugs in pecan.


Insecticides Labeled for Pecan

Aldicarb

Azadrachtin

Carbaryl

Chlorpyrifos

Cypermethrin

Endosulfan

Esfenvalerate

Fenbutatin-oxide

Hexythiazox

Imidacloprid

Malathion

Methomyl

Phosmet

Pyridaben

Insecticides Used on Pecans

Crop

Class

Insecticide

Trade Name

% Acres Treated as Reported
by growers in 1991

% Acres Treated In 2002

Avgerage # Applications

Pecan

Insecticide

Carbaryl

Sevin 80S

7

15

1

Pecan

Insecticide

Chlorpyrifos

Lorsban 4E, or 50W

22

25

2

Pecan

Insecticide

Cypermethrin

Ammo 2.5 EC, Cymbush

5

3

1

Pecan

Insecticide

Endosulfan

Phaser 3EC or 50WBS, Thiodan 3EC or 50WP

17

20

1

Pecan

Insecticide

Esfenvalerate

Asana XL

7

12

1

Pecan

Insecticide

Fenbutatin-oxide

Vendex 50WP

Not reported

20

1

Pecan

Insecticide

Malathion

Malathion 5E or 8EC

7

10

1

Pecan

Insecticide

Phosmet

Imidan 70W

Not reported

20

1

Pecan

Insecticide

Dimethoate

Cygon

17

20

1



Weeds

Management of weeds in native pecan groves consists of mowing the permanent ground cover and/or grazing by livestock. Weed control in pecan orchards with improved varieties is more intensive and is required for attainment of maximum yield. Weeds interfere with pecan production by competing for moisture and nutrients, producing chemicals that inhibit tree growth (allelopathy), and decreasing mechanical harvesting efficiency. The most commonly used system of orchard weed control is a herbicide strip in the tree row with mowed sod row middles. Maintenance of row middles in sod improves orchard access during wet conditions and mowing reduces competition with the trees. Cultivation is generally not practiced due to concerns about erosion and reduced tree health and growth.


Herbicides Labeled for Pecan
Preemergence Control

Diuron

Isoxaben

Napropamide

Norflurazon

Oryzalin

Simazine


Postemergence Control

2,4-D Amine

Fluaziflop

Glyphosate

Paraquat

Sethoxydim


Herbicides Used on Pecans

Crop

Class

Herbicide

Trade Name(s)

% Accres Treated as Reported by growers in 1991

% Acres Treated in 2002

Avgerage # Applications

Pecan

Herbicide

Diuron

Karmex 80WDG

Not reported

10

1

Pecan

Herbicide

Glyphosate

Roundup Ultra

6

65

1

Pecan

Herbicide

Oryzalin

Surflan 4AS, Oryzalin 4AS

Not reported

5

1

Pecan

Herbicide

Paraquat

Gramoxone Extra, BOA

2.5

10

1

Pecan

Herbicide

Simazine

Princep 4L, Princep 90WDG

Not reported

10

1



Diseases

Pecan Scab
Cladosporium caryigenum (Ell. et Lang.) Gottwald

Pecan scab is the most destructive and widespread disease of pecans and hickories. Damage can vary due to weather and cultivar. Pecan scab symptoms show up as small round, olive-green to black spots on the new leaflets, petioles and nut shuck tissue. These lesions can grow together resulting in large irregular masses of black on the leaflets and nuts causing terminal death. New tissue is more susceptible than older tissue. Old lesions tend to dry out, crack and fall out of the leaf blade making it look tattered. Old lesions, later in the season, can become covered with other fungi resulting in a white moldy look. Pecan scab overwinters on the shucks and shoots that were infected the previous season. Infections can occur as soon as green tissue appears in the spring and continue throughout the season on any growing tissue. Water and air currents can spread the spores from orchard to orchard. Spores can germinate and infect pecan tissue with 2-12 hours. Nuts attacked shortly after nut set usually abort and fall. Nut shuck infected early in the season often crack where lesions run together and serve as entry points for other fungi. Nut infection can result in crop loss from nut drop and small sizing of nuts.

Control: Preventive fungicide control is the most effective way to control pecan scab. Pecan orchards that use scab-resistant or tolerant cultivars may use a modified fungicide program unless wet conditions prevail. The following compounds are registered for pecan scab: Abound, Dodine, Enable, Orbit/Super Tin AGPAK, Syllit and Topsin-M.


Shuck Decline/Dieback unknown causal agent

and Stem End Blight unknown causal agent

Shuck decline is also know as dieback, tulip disease, and shuck disease. The causes of both these diseases are unknown. Both problems can appear on the same nut cluster and even on the same nut. Some nuts on a cluster can be affected while others remain healthy.

Shuck dieback is more prevalent than stem end blight. Shuck dieback is generally most severe on trees with large crops and with crowded trees. The shuck will turn black and die at or near the tip of the nut. The blackened area can spread over the entire shuck and the shuck will usually flare open. Tree stress factors can increase the incidence of shuck dieback. Stem end blight begins as a brown or black spot on the shuck near the base of the nut. This black area usually enlarges to cover a portion of the nut, even the entire nut. After the black area appears, the nut can easily be dislodged from the stem. The earlier either of these disease symptoms appears, the poorer the kernel quality.

Control: Fungicides are not effective in controlling shuck dieback. The following compound is labeled for control of stem end blight: Topsin-M.


Vein Spot
Gnomonia nerviseda Cole

Vein spot lesions are very similar to those caused by pecan scab but tend to be linear rather than round. The lesions first appear as dark brown-black pinpoint spots centered on veins on midribs. Vein spot lesions appear shiny or greasy in sunlight. These lesions seldom increase in size beyond 0.25-inch in diameter. This fungus overwinters in infected leaf debris on the ground. In the spring spores are released into the air immediately after rain. Some pecan cultivars are more susceptible than others are but all cultivars have some level of susceptibility to vein spot.

Control: This disease is usually controlled during pecan scab sprays. The following compounds are labeled for control of Vein spot: Dodine, Enable, Orbit/Super-Tin AGPAK, Syllit and Topsin-M.


Fungal Leaf Scorch
unknown causal agent

Fungal leaf scorch is a major cause of premature defoliation of pecans in the southeast. This infection can be mistaken for nutritional imbalances such as excessive nitrogen and potassium. The exact cause of this disorder is unknown. Fungus is believed to be the cause, since it can be isolated from the scorched tissue. The scorch tissue is brown and drying beginning at the leaf margin and expanding inward. There is a black or very dark band separating the scorched areas from the green portions. Scorched leaflets will drop prematurely.

Control: Select cultivars that are resistant to fungal leaf scorch. Fungicides can reduce but not prevent fungal leaf scorch. The following compounds are labeled for control of leaf scorch: Enable, Orbit/Super-Tin AGPAK.


Pecan Bunch Disease
Mycoplasma-like organism

Bunch disease of pecans is a disease that affects weak pecan trees and is caused by a mycoplasma-like organism. It is most often associated with pecans grown along alluvial river bottoms. Seedling pecans appear to be a source of inoculum. Affected trees display a proliferation of stem shoots on large scaffold limbs, localized on individual limbs. The shoots on the limbs are brittle and short-lived. Leaves on the infected shoots are larger than normal and flexible. This disease causes lower yields and inferior nut quality. Symptoms can occur on a healthy tree that is grafted with a diseased scion. Zinc deficiency can also cause bunching symptoms and can be confused with bunch disease. The two conditions can be distinguished on the basis of foliage symptoms. Zinc deficient leaves are smaller and very rigid with chlorosis developing between the veins.

Control: Bunch disease can be controlled by pruning, removing infected trees and planting resistant cultivars. Pruning can be effective only when a few scattered bunches are present. When pruning make the cuts several inches below the bunch symptoms to ensure that all the infected area is removed.


Fungicides Labeled for Pecan

Azoxystrobin

Dodine

Fenbuconazole

Propiconazole and Triphenyltin Hydroxide

Thiophanate


Fungicides Used on Pecans

Crop

Class

Fungicide

Trade Name

% Acres Treated as Reported
by Growers in 1991

% Acres Treated In 2002

Avgerage # Applications

Pecan

Fungicide

Fenbuconazole

Enable 2F

Not reported

10

1

Pecan

Fungicide

Propiconazole + triphenyltin hydroxide

Orbit 45WP/Super-Tin 80WP AGPAK

7

60

1



Contacts

Profile Compiled By:

Dr. Donn Johnson
Department of Entomology
319 Agriculture Building
University of Arkansas
Fayetteville, AR 72701
Phone: 479-575-2501
Fax: 479-575-2452
E-mail: dtjohnso@uark.edu

Dr. R. Keith Striegler
Department of Horticulture
316 Plant Science Building
University of Arkansas
Fayetteville, AR 72701
Phone: 479-575-2790
Fax: 479-575-8619
E-mail: kstrig@uark.edu

Barbara A. Lewis
Department of Entomology
319 Agriculture Building
University of Arkansas
Fayetteville, AR 72701
Phone: 479-575-3398
Fax: 479-575-2452
E-mail: balewis@uark.edu

Contact Personnel:

Ples Spradley

Pesticide Assessment Specialist
Cooperative Extension Service
University of Arkansas
P.O. Box 391
Little Rock, AR 72203
Phone: 501-671-2234
Fax: 501-671-2303
E-mail: pspradley@uaex.edu



References

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  2. Carroll, B., M.W. Smith, and B.D. McCraw. 1998. Establishing a pecan orchard. Oklahoma State Univ. Coop. Ext. Ser. F-6247. 4 pp.

  3. Klugh, B.F. and D. Rundle. 2003. Arkansas Statistical Summary – Fruits/Nuts/Vegetables. Arkansas Agricultural Statistics Service, Little Rock, AR.

  4. Patterson, W.K. 1994. Culture and care of pecan trees in Arkansas. Univ. of Ark. Coop. Ext. Ser. Fact Sheet A6040. 6 pp.

  5. Scott, R.C., J.W. Boyd, and K.L. Smith. 2003. Recommended chemicals for weed and brush control. Univ. of Ark. Coop. Ext. Ser. Misc. Publication 44. 154 pp.

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  7. Smith, M.W., B.S. Cheary, and B.L. Carroll. 2002. Fescue sod suppresses young pecan tree growth. HortScience 37(7): 1045-1048.

  8. Smith, M.W., M.E. Wolf, B.S. Cheary, and B.L. Carroll. 2001. Allelopathy of bermudagrass, tall fescue, redroot pigweed, and cutleaf evening primrose on pecan. HortScience 36(6): 1047-1048.

  9. Turner, J. 2003. Establishment and maintenance of landscape pecan trees in southwest Arkansas. Univ. of Ark. Coop. Ext. Ser., Miller County, Texarkanna, AR. 10 pp.

  10. Turner, J. 2003. Pecan production in southwest Arkansas. Univ. of Ark. Coop. Ext. Ser., Miller County, Texarkanna, AR. 16 pp.

  11. University of Arkansas Cooperative Extension Service. 2003. Insecticide Recommendations for Arkansas. Univ. of Ark. Coop. Ext. Ser. Misc. Publication 144. 216 pp.

  12. University of Georgia Cooperative Extension Service. 2000. Pecan pest management handbook. www.gaipm.org/pecan/scout/.

  13. Vann, S. and P. Fenn. 2003. Diseases of Pecan, p. 26, In: R. Cartwright (ed.). Arkansas Plant Disease Control Products Guide - 2003. Univ. of Ark. Coop. Ext. Ser. Misc. Publication 154.

  14. vonBroembsen, S. 2001. Pecan diseases: prevention and control. Oklahoma State Univ. Coop. Ext. Ser. F-7642. 6 pp.

  15. vonBroembsen, S., P. Mulder, and B.D. McCraw. 2003. Commercial pecan insect and disease control – 2003. Oklahoma State Univ. Coop. Ext. Ser. CR-6209. 4 pp.