T. A. Lee Pecan Disease Management Mark Black, Texas AgriLife Extension Service, Uvalde
Scab Downy spot Powdery mildew Pecan diseases Crown gall Cotton root rot Root knot Kernel decay & contamination
Kernel decay or contamination Fungi, bacteria Contact with soil Moisture from soil, green leaves & shucks High temperatures Transit, drying, storage Mycotoxins Escherichia coli, Salmonella spp. from feces -- grazing, wildlife
Pecan diseases Scab Downy spot Powdery mildew Sardanelli and Ellison, UMD Crown gall Cotton root rot Root knot Jon Eisenback, VPISU
Root knot, M. Black
Root knot; J. Johnson
Root knot, T.A. Lee
Root knot, T.A. Lee
J.A. Brito et al, 2006
Brito et al., 2006, Florida
Root knot nematode Meloidogyne partityla --Exclusion --Increased management, limit nut load --Freeze vulnerable? --Temik? --Terminate orchard Root knot
Scab Downy spot Powdery mildew Crown gall Cotton root rot Pecan diseases
Cotton root rot of Pecan -- a rootstock issue
Peanut
Apple
Apple
Scab Downy spot Powdery mildew Crown gall Pecan diseases
Crown gall (Bill Ree)
Crown gall, T.A. Lee
Scab Downy spot Powdery mildew Pecan diseases T. A. Lee
Powdery mildew UGA
Scab Downy spot Pecan diseases J. Johnson
Jason Brock, U. Georgia
Downy spot; Wichita vs. Western Schley
Downy spot; Wichita vs. Western
Downy spot
Downy spot; leaf scorch
Downy spot; Cape Fear, partial resistance
Winter Summer Winter Leaf debris Leaf debris ascospores Downy spot Leaf??? conidia
Downy spot Leaves only Defoliation Infection - late April to late June Variety partial resistance Fungicides (scab program)
Table 2. Variety reaction to downy spot Most susceptible -- Western, Pawnee, Desirable, Delmas, Moneymaker, Stuart Moderately susceptible -- Wichita, GraBohls, Cheyenne, Barton Moderately resistant -- Choctaw, Caddo, Mohawk, Kiowa, GraKing, Success, Cape Fear
Pecan diseases Scab Jason Brock, U. Ga.
Mature leaflets resistant to Scab
Shucks susceptible to Scab until late T. A. Lee
Shuck scab lesions depressed
Scab lesions with secondary fungus
Jerry A. Payne
Reduced nut size > Early nut drop > Lower % kernel > Leaf drop > Twig death Jason Brock, UGA
1-3 days 2 weeks resistant http://www.tifton.uga.edu/pecan/scab%20pictures.htm
Scab fungus Overwinter - shuck, leaf (rachis, petiole), twig Management - decay; pulverize shuck, leaf @ harvest. Tree removal. Infection - 50-95 F (59-77 F) & >2-4 hr (>12 hr) leaf wetness Lesion - 7-9 days; expand 7-14 days Alert - spring & late summer; frequent showers (# events > total) Fungicides - variety, prophylactic, rotate / mix
Winter Summer Winter Debris, twig Shuck Leaf, twig Debris, twig Scab
Scab risk Region east to west gradient LA to CA Site, Management fungus life cycle Variety minimize susceptible, maximize resistant, diversity Weather frequent rains, mild temperatures AU-Pecan (www.awis.com) 0.1 rains and % rain chance for 5 days; by variety scab resistance level
Table 1. Variety reaction to scab Susceptible -- Apache, Hopi, Western, Wichita Moderately resistant -- Cheyenne, Desirable, Forkert, Oconee, Pawnee, Sioux, Waco More resistant -- Caddo, Choctaw, Elliott, Kanza, Melrose, Nacono, Osage [Apalachee, Lakota, Mandan]
Scab is not.
Scab Stress J. W. Stewart
Leaf scorch after drought stress; J. W. Stewart
Chemical injury T. A. Lee
Vein spot T. A. Lee
TPTH (30) Triazole (3) Strobilurin (11) Oxathiin (7) Dodine (M7) Super Tin, Agri Tin mixtures Enable, Folicur, Orbit, Quash Abound, Heritage Headline, Sovran Elast mixtures Fungicide big picture Stratego Quilt Adament Quadris Top Pristine 3 + M7; 30 + M7
Fungicide dilemma or opportunity? Class (group) Move? Activity Triazole (3) local cure > protect Strobilurin (11) local cure < protect TPTH (30) no protect Dodine (M7) no protect
Program for nut scab? Post-pollination is the critical period for protection. Decide what you want to spray during this time, and work from there 4 possibilities Adapted from Jason Brock, U. Georgia
April/May Enable or Propimax Headline or Sovran Stratego, Quilt, QuadrisTop DMI + Tin April/May Enable or Propimax Headline or Sovran Stratego, Quilt, QuadrisTop DMI + Tin June/July Tin or Elast + Tin June/July Tin or Elast + Tin Elast + Enable August Tin or Elast + Tin August Tin or Elast + Tin
DMI + Tin April/May April/May Headline or Sovran Stratego or Quilt June/July June/July Stratego or Quilt DMI + TIN August Tin or Elast + Tin August Tin or Elast + Tin
Questions?