Diseases of and Fungicides Labeled for Control Disease Fungicides a (Cladosporium sp.) Symptoms: Early leaf infections produce pinpoint olive brown lesions often on veins of undersides of leaves. Spots enlarge and coalesce until large areas of leaves may become almost black. Lesions on nuts are small, black and circular, slightly raised at first but later sunken. The entire surface of nuts of highly susceptible varieties may appear black from extensive infections. Source of Inoculum: Fungus may overwinter in infested s, leaf stems or leaves. The fungus is spread by wind borne spores and is boosted by high humidity. Control: Knock off old s and stems before spring. Prune out low limbs to improve air circulation in orchard. Follow Pecan Spray Schedule. Downy Spot (Mycosphaerella sp.) Symptom: Appears in late spring or early summer as downy spots on the undersides of the leaflets. Later, greenish white spots about 1/8 inch in diameter are visible on both sides of the leaves. As the season advances, the color of the spots changes to brown. Source of Inoculum: Fungus lives from year to year in infected leaves. Control: Follow Pecan Spray Schedule. Vein Spot (Gnomonia sp.) Symptoms: Spots may originate on vein of leaflets or on leaf stem and are dark brown to black in final stages. On lateral veins, lesions are circular or oval and seldom attain a diameter of more than 1/4 inch. On midribs of leaflets and on leaf stems, spots are long and narrow. When the disease is severe, premature defoliation usually occurs. Source of Inoculum: Fungus lives through the winter on fallen leaves. Control: The pre pollination spray and first cover sprays are essential for control. Brown Spot (Cercospora sp.) Symptoms: Early leaf spots are circular, reddish brown and often develop grayish concentric zones. Spots become irregular later. Nuts are not infected by this fungus. Usually a problem only when trees lack vigor or where rainfall is unusually high. Premature defoliation often occurs when disease is severe. Abound (azoxystrobin) Absolute, Adament(tebuconazole + trifloxystrobin) Headline (pyraclostrobin) Orbit, Propimax, Bumper (propiconazole) Quash (metconazole) Quilt (azoxystrobin + propiconazole) Sovran (kresoxim methyl) Stratego (propiconazole + trifloxystrobin) Ziram (ziram) Orbit, Propimax, Bumper (propiconazole) b Quilt (azoxystrobin + propiconazole) b Orbit, Propimax, Bumper (propiconazole) b Quilt (azoxystrobin + propiconazole) b
Disease Fungicides a Source of Inoculum: Fungus lives from year to year in infected spots on the old leaves. Spores are wind borne. Control: Fertilize trees to improve vigor. Follow Pecan Spray Schedule. Powdery Mildew (Microsphaera sp.) Symptoms: This disease affects both foliage and nuts, forming a white superficial fungal growth early in the growing season. Source of Inoculum: Lives from year to year on old infected leaves and s. Control: Include sulfur in the June, July and August sprays at the rate of 6 pounds per 100 gallons or follow Pecan Spray Schedule. Orbit, Propimax, Bumper (propiconazole) b Quilt (azoxystrobin + propiconazole) b Leaf Scorch (Xylella fastidiosa) Symptoms: Begins in midsummer, becoming prevalent by late summer. A tan necrosis begins on leaflet tips or margins and advances in an irregular pattern toward the center of the leaflet. Infected leaflets turn tan, curl and drop from tree, which may be completely defoliated in some instances. Scorch can be caused by a bacterium (Xylella fastidiosa), but other forms of scorch may be caused by such factors as environmental stresses or nutritional imbalances. Source of Inoculum: The bacterium is present in a wide variety of plants, many of which may be symptomless. It is vectored by xylem feeding insects. Control: Maintaining trees in good nutritional balance may give some control. Bunch Disease (phytoplasma) Symptoms: Affected trees have a bushy growth of slender, willowy shoots. The bunch growths are most conspicuous in spring because they leaf out about two weeks earlier than healthy branches. Control: Never use bud or scion wood from affected trees for propagation. Pruning out diseased branches may help arrest the disease. Destroy severely affected trees. Rosette (Zinc deficiency) Symptoms: Nonvisible zinc deficiencies are known to limit yields through reduced flower formation, excessive blossom drop, poor filling and premature defoliation. Visible symptoms include yellowish mottling of leaves, primarily in top branches, with narrow and crinkled leaflets sometimes having perforations between the veins. Severe deficiencies appear as shortened internodes on new growth, some dieback of terminals and a bunching or rosetting effect. No pathogen involved. Control: Leaf zinc levels should be determined by foliar analysis. Several sprays of 2 3 pounds of 36 percent zinc sulfate or 2 to 4 quarts of NZN should be applied to correct deficiencies indicated by the analysis. In acidic soils, dry zinc sulfate salts may be applied to the soil at 0.25 0.50 pounds per inch of trunk diameter. Use the smaller amounts on sandy soils. In alkaline soils, application of zinc salts to the soil is not effective. Adequate leaf zinc levels must be maintained by foliar or soil applications as determined by annual foliar analysis. a Trade name (chemical name) b Tank mix with another registered fungicide.
Louisiana Recommendations for the Control of Pecan Diseases The control of diseases and insects is essential for profitable pecan production in Louisiana. Commercial pecan producers must spray at the proper time with recommended fungicides and insecticides. Learning to identify the major insect pests and diseases of pecans is highly desirable and strongly recommended. To obtain adequate disease control and receive maximum benefit from applied fungicides, spray applications must be made on a preventive program. In addition to spraying, cultural practices and sanitation can reduce the severity of certain insects and disease problems. These practices should be followed by both commercial growers and homeowners with only a few trees. Sanitation: Certain leaf diseases, such as scab, and insects, such as the hickory worm, overwinter on s and leaves. If these are raked and burned, it will help to reduce the severity of these problems to some extent the following year. Prune dead and broken limbs from trees to remove potential habitats for certain insects and diseases. Fertilization: Proper fertilization will increase production and boost pest control. Well maintained pecan trees are less susceptible to attack by certain diseases and insects. Consult the LSU AgCenter s Louisiana Cooperative Extensive Service for information on leaf and soil sampling techniques, fertilization and cultural practices. Spray Equipment: Good spray coverage is essential for good disease control and, to a lesser extent, for insect control. A large air blast sprayer (speed sprayer) has proven very satisfactory for treating large acreages of pecan trees for control of insects and diseases. Caution: The potential for developing strains of pathogens resistant to fungicides is very great in pecan production. To avoid this: 1. Alternate fungicides with different modes of action in the spray program. 2. Do not use several consecutive sprays with one fungicide or similar fungicides. 3. Avoid using higher rates of fungicides than those recommended. Proper calibration is essential.
Fungicide Spray Schedule for Spray Time of Application Target Disease First Pre pollination Second Pre pollination First Cover Spray When leaves are at least 1 inch long When leaves have grown (or 10 14 days after first spray) 2 3 weeks after previous spray Vein Spot Downy Spot Vein Spot Downy Spot Zinc Maintenance Vein Spot Downy Spot Zinc Maintenance Second Cover Spray 2 3 weeks after previous spray Third Cover Spray 2 4 weeks after previous spray Fourth Cover Spray 2 3 weeks after previous spray Fifth Cover Spray a 3 4 weeks after previous spray Sixth Cover Spray a,b a May be omitted if weather is dry. b Do not apply fungicides after Pecan Fungicides by FRAC ing 3 11 3 & 11 30 M7 1 Bumper Abound Absolute Agri Tin Elast T Methyl Enable Headline Adamant Super Tin Monsoon Sovran Quadris Top Thiophanate Methyl Topsin 1 + 3 Topsin XTR 33 Agri fos Fosphite Fungiphite Orbit Quilt Topsin M K phite Orius Quilt Xcel Phostrol Propimax Stratego Prophyt Quash Tebuzol Tilt Rampart M3 Ziram
Fungicides Labeled for Use on Common Trade Formulation(s) Rate(s) (per Acre) Comments FRAC PHI (days) azoxystrobin Abound 2.08F 6.2 12.3 fluid 7 to 21 day interval; no three applications or 2.31 quarts or 2.4 pounds per acre per season 11 45 azoxystrobin + difenoconazole Quadris Top 2.72F 8 14 fluid 14 to 21 day interval; no 56 fluid per acre per crop 11 + 3 45 azoxystrobin + propiconazole Quilt Quilt Xcel 1.66F 2.2F 14 27.5 fluid 14 21 fluid Use higher rates for scab prior to and during nut formation; use in tank mix for other leaf spots; 14 day interval; no more than twp consecutive applications; no more than four applications or 122 fluid per acre per season; do not graze livestock in treated orchards 11 + 3 45 ) dodine Elast 400F 3 pints 10 to 21 day interval; no more than six applications or 18 pints per acre per year M7 Do not fenbuconazole Enable 2F 8 fluid 10 to 21 day interval; no more than 1.5 quarts per acre per season; do not graze livestock in treated orchards 3 28 ) kresoximmethyl Sovran 50WDG 2.4 4.8 14 to 21 day interval; no more than 25.6 per acre per season 11 45 metconazole Quash 50WDG 2.5 3.5 No more than two applications after petal fall; no more than four applications or 16 per acre per season 3 25
Common Trade Formulation(s) Rate(s) (per Acre) Comments FRAC PHI (days) phosphite (phosphorous acid salts) Agri fos, Fosphite, Fungi phite, K phite, Phostrol, Prophyt, Rampart Phosphorous acid equivalent (lb/gal) 3.35 3.9 1 2 quarts 1 3 quarts 7 to 14 day interval; use in 100 gallons of water; see label for specifics 33 0 propiconazole Bumper, Monsoon, Orbit, Propiconazol e,propimax, Tilt 3.6EC 4 8 fluid Use higher rates for scab prior to and during nut formation; use lower rates in tank mix for other leaf spots; 14 day interval; no more than two consecutive four applications or 32 fluid per acre per season; do not graze livestock in treated orchards 3 Do not propiconazole + trifloxystrobin Stratego 2.08EC 10 fluid 14 to 21 day interval; no three applications or 30 fluid per acre per season 3 + 11 30 ) pyraclostrobin Headline 2.09F 6 7 Use in pre pollination and first cover sprays; 14 day interval; no more than two sequential applications; no more than four applications or 28 fluid per acre per season 11 14 tebuconazole Orius, Tebuzol 3.6 F 4 8 fluid 10 to 14 day interval; no more than 32 fluid per acre per season; tankmix low rate with Super Tin; see label 3 Do not tebuconazole + trifloxystrobin Absolute, Adament 500 SC 50 WG 5 7.67 fluid 4 8 7 to 14 day interval; no four applications or 32 per acre per season; do not graze livestock in treated orchards 3 + 11 60 )
Common Trade Formulation(s) Rate(s) (per Acre) Comments FRAC PHI (days) thiophanatemethyl Thiophanat e methyl, Topsin, T Methyl 4.5 FL 70 WP 85 WDG 20 fluid 1 pound 0.4 0.8 pound 3 to 4 week interval; no more than 60 fluid, 3 pounds or 2.5 pounds per acre per season, respectively 1 Do not thiophanatemethyl + tebuconazole Topsin XTR 4.3F 25 fluid 21 day interval; alternate after each application; REI = 3 days 1 + 3 Do not triphenyltin hydroxide Agri Tin Super TIn 80WP 5 7.5 2 to 4 week interval; no more than nine applications or 45 per acre per season 30 30 ziram Ziram 76DF 3 4 pounds No more than 64 pounds per acre per season M3 55