Pecan

Carya illinoensis

Scab

Fungal pathogen

Cladosporium caryigenum, (prev. Fusicladium effusum, Cladosporium effusum)

Area(s) affected

Leaves, nuts and green twigs

Signs/Symptoms

Small, circular, olive-green to black spots form on the lower surface of the leaf and nuts. These spots may have a velvety or cracked appearance. Sometimes these spots coalesce forming large, irregularly shaped darkened areas. On nuts, these spots appear to be sunken in. Infected twigs will exhibit elongated spots parallel to the twig axis. Infected foliage may prematurely drop. When infection is severe, the entire nut surface is black, development is arrested and the nut drops prematurely or fails to grow in the area of infection.

Photo credit: University of Georgia Plant Pathology Archive, University of Georgia, Bugwood.org

Photo credit: University of Georgia Plant Pathology Archive, University of Georgia, Bugwood.org

Photo credit: University of Georgia Plant Pathology Archive, University of Georgia, Bugwood.org

Photo credit: University of Georgia Plant Pathology Archive, University of Georgia, Bugwood.org

For more information

http://pecankernel.tamu.edu/diseases/#scab

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Brown Leaf Spot

Fungal pathogen

Sirosporium diffusum, (syn. Cercospora fusca)

Area(s) affected

Leaves                               

Signs/Symptoms

Circular, reddish brown spots form on the upper and lower leaf surface. Older spots will turn gray and concentric circles will form within the spot. If the disease is not controlled the tree will lose its leaves.

For more information

http://pecankernel.tamu.edu/diseases/#brown

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Vein Spot

Fungal pathogen

Gnomonia nerviseda

Area(s) affected

Leaves

Signs/Symptoms

Smooth, dark brown to black spots form on the vascular structures of the leaf which include: veins, midribs, petioles, and rachises. In the sun, these spots appear greasy or shiny. Premature defoliation will occur. This infection often resembles pecan scab lesions.

For more information

http://pecankernel.tamu.edu/diseases/#vein

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Leaf Blotch

Fungal pathogen

Mycosphaerella dendroides

Area(s) affected

Leaves                               

Signs/Symptoms

Faint yellow spots develop on the upper leaf surface; these spots eventually turn dark brown. Small, olive-green spots with a velvety appearance form on the lower leaf surface. Premature defoliation may occur.

For more information

http://pecankernel.tamu.edu/diseases/#leaf

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Crown Gall

Bacterial pathogen

Agrobacterium tumefaciens

Area(s) affected

Trunk and roots                

Signs/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.

Photo credit: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

Photo credit: Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Downy Spot

Fungal pathogen

Mycosphaerella caryigena

Area(s) affected

Leaves                               

Signs/Symptoms

Circular, light yellow spots form on the lower leaf surface. These spots may be covered with a white fuzzy growth. As the disease progresses, these spots become visible on the upper leaf surface. The upper leaf surface spots are yellow, while the lower leaf surface spots turn golden brown. Premature defoliation may occur.

For more information

http://pecankernel.tamu.edu/diseases/#downy

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Powdery Mildew

Fungal pathogen

Microsphaera penicillata

Area(s) affected

Nuts and leaves

Signs/Symptoms

A white powdery growth develops on infected nut shucks and leaves.

Photo credit: Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org

Photo credit: Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Pecan Bacterial Leaf Scorch (BLS)

Fungal pathogen(s)

Xylella fastidiosa, Phomopsis sp., and Glomerella cingulata

Area(s) affected

Leaves                               

Signs/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.

Photo credit: Rebecca A. Melanson, Louisiana State University AgCenter, Bugwood.org

Photo credit: Rebecca A. Melanson, Louisiana State University AgCenter, Bugwood.org

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Bunch Disease

Causal agent

Phytoplasma

Area(s) affected

Shoots

Signs/Symptoms

Trees affected with bunch disease show a typical bunching symptom, caused by excessive growth of lateral buds. This results in a dense growth of thin shoots and leaves that resembles a witches’ broom.

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Parasitic and Epiphytic Plants

Causal agent(s)

Fungus-algae complex, Tillandsia usneoides, Tillandsia recurvata

Area(s) affected

Trunk and branches         

 

Lichens: Gray to green plant that typically forms crustlike, leaflike, or branching growth on trees.

Photo credit: USDA Forest Service - Northeastern Area Archive, USDA Forest Service, Bugwood.org

Photo credit: USDA Forest Service – Northeastern Area Archive, USDA Forest Service, Bugwood.org

Spanish Moss: A long, whisker-like plant that hangs from trees.

Photo credit: Wendy VanDyk Evans, Bugwood.org

Photo credit: Wendy VanDyk Evans, Bugwood.org

Ball Moss: It first occurs as small, gray green tufts that develop within a relatively short time into a dense “ball” composed of numerous individual plants. The plants form root-like holdfasts which penetrate into the rough bark of the tree. These holdfasts often completely encircle a limb.

Photo credit: Karan A. Rawlins, University of Georgia, Bugwood.org

Photo credit: Karan A. Rawlins, University of Georgia, Bugwood.org

For more information

http://www.fs.fed.us/wildflowers/beauty/lichens/

https://plants.usda.gov/plantguide/pdf/cs_tius.pdf

http://texasforestservice.tamu.edu/main/popup.aspx?id=1264

Articularia Leaf Mold

Fungal pathogen

Articularia quercina

Area(s) affected

Leaves                               

Signs/Symptoms

A growth of white tufts develops on the lower leaf surface.

For more information

 

Pink Mold

Fungal pathogen

Trichothecium roseum

Area(s) affected

Nuts                                   

Signs/Symptoms

Pink mold will develop on nuts that are infected with the pecan scab fungus. A white to pink, moldy growth will develop in old scab lesions. If the fungus invades the kernel, it becomes oily and produces a rancid odor.

For more information

http://pecankernel.tamu.edu/diseases/#pink

 

Cotton Root Rot

Fungal pathogen

Phymatotrichopsis omnivorua, (syn. Phymatotrichum omnivorum)

Area(s) affected

Roots                                  

Signs/Symptoms

Infected trees die suddenly. Root bark is decayed and brownish, and bronze colored wooly strands of the fungus are frequently visble on the root surface. Leaves will turn yellow or brown and will remain attached to the tree.

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Shuck Decline (Shuck Dieback)

Causal agent

Unknown, possibly physiological stress or hormonal imbalance

Area(s) affected

Nuts                                   

Signs/Symptoms

A dark, thin line forms on the inner surface of the shuck, at the junction with the shell. The inside of the shuck turns dark green and slimy and the dark, thin line progresses toward the exterior. The outer surface of the shuck has a shiny, water-soaked appearance. Beginning at the distal end, the shuck turns brown and then eventually black. The shuck may peal back at the distal end, resembling a tulip.

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Shuck and Kernel Rot

Fungal pathogen

Phytophthora cactorum

Area(s) affected

Nuts                                   

Signs/Symptoms

Fruit rot begins at the stem end of the fruit and progresses to the tip of the shuck rapidly. The shuck will turn black and become soft and moist. Kernels are inedible.

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Stem-End Blight

Fungal pathogen

Unknown, suspect Botryosphaeria dothidea, (syn. Botryosphaeria ribs)

Area(s) affected

Nuts                                   

Signs/Symptoms

Black, sunken, shiny spots form at or near the stem-end of the shuck. As the spots enlarge, the shuck will be completely black and the liquid in the kernel turns brown.

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Root Knot Nematode

Pathogen

Meloidogyne spp.

Area(s) affected

Roots                                  

Signs/Symptoms

Feed on the inside of the roots inducing knots or galls on them. These swellings are usually white and round to irregularly elongated. Foliage may wilt, appear stunted, and turn yellow or bronze.

Photo credit: David B. Langston, University of Georgia, Bugwood.org

Photo credit: David B. Langston, University of Georgia, Bugwood.org

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Kernel Discoloration

Fungal pathogen

Nematospora spp.

Area(s) affected

Nuts                                   

Signs/Symptoms

Kernels develop dark spots and may become rotted. Stinkbugs can also cause dark brown to black spots on the kernels.

For more information

Teviotdale, Beth L., Themistocles John. Michailides, and Jay William. Pscheidt. Compendium of Nut Crop Diseases in Temperate Zones. St. Paul, MN: American Phytopathological Society, 2002. Print.

Fungal Twig Dieback

Fungal pathogen

Botryosphaeria berengeriana

Area(s) affected

Branches

Signs/Symptoms

Infected branches are covered with small raised pustules with black centers.

For more information

 

For additional support and current disease management information, contact your local AgriLife Extension Office: http://counties.agrilife.org/

Content editor: Corinne Rhodes, Undergraduate Extension Assistant, Texas Plant Disease Diagnostic Laboratory.  This project was performed to satisfy BESC485 requirement under the supervision of Dr. Kevin Ong,  kevo@tamu.edu, Director, Texas Plant Disease Diagnostic Laboratory, Texas A&M University, Texas AgriLife Extension Service (April 25, 2014)

Print Friendly

Comments are closed.