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Transcript of MARCH PLANT DISEASES FROM THE AUBURN PLANT DIAGNOSTIC LAB · PDF file ·...

  • EXTENSION PLANT PATHOLOGY, EXTENSION HALL, AUBURN UNIVERSITY, AL 36849-5624

    April 15, 2005 PP-588

    MARCH PLANT DISEASES FROM THEAUBURN PLANT DIAGNOSTIC LAB

    MARCH PLANT DISEASES FROM THEBIRMINGHAM PLANT DIAGNOSTIC LAB

    MARCH INSECT SAMPLES AT THE AUBURNPLANT DIAGNOSTIC LAB

    DISEASE POSSIBILITIES FOR APRIL

    LAB NOTES

    Jackie MullenExtension Plant Pathology Specialist-Auburn

    Jim JacobiExtension Plant Pathology Specialist-Birmingham

    Charles RayResearch Fellow IV-Auburn

    Auburn Plant Disease Report-March (J. Mullen)

    In March, we received 54 plant samples for problem/disease diagnosis. Diseasesseen last month included cane & leaf rust on blackberry, brown patch on centipede and St.Augustine, anthracnose on Carex, Rhizoctonia crown & root rot on daylily, Pestalotiopsisleaf spot on holly, Pestalotia and Rhododendron leaf spot on palm and Asian jasmine, ruston oats, crown gall on pecan, black knot on plum, and powdery mildew on wheat.

    Pestalotia and Pestalotiopsis leaf spots are often seen in early spring on winter-stressed or injured foliage. These fungi are often called weak disease agents, since theybecome established only on weakened foliage. Disease control treatments are usually notneeded.

    Black knot, caused by the fungus Plowrightia morbosum, is a common disease of

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    plums and cherry trees. The fungus causes elongated swellings on twigs and branches. These swellings are initially green. Eventually, the fungus produces a black mold thatcovers the swollen plant tissues. If not controlled, this disease could cause the death of thetree after several years. Fungal spores are produced in the spring and are spread by watersplash and wind. Damaged branches should be removed and destroyed. Liquid lime sulfurmay be applied in late winter. Protective sprays of Captan can be used throughout thegrowing season until harvest.

    There are five different rust diseases that affect Rubus species. They can bedistinguished by symptoms, signs, and their host preferences/range. Cane and leaf rust wasnoted on blackberry, and this disease can be of economic importance in the Southeast. Raspberries rarely develop this disease. Leaf infections can cause leaf drop which is themajor impact of the disease. Yellow uredia will split the bark of floricanes in the spring. Yellow uredia will also develop on lower leaf surfaces. The urediospores are yellow and arethe more prominent of the 5 spores stages this fungus produces. In the fall, damaged canesshould be cut back. Liquid line sulfur may be applied in the late winter. During the growingseason, protective fungicide sprays are recommended.

    Leaf spot diseases of rhododendron are common. Many fungal leaf spot pathogens ofrhododendron cause brown circular-irregular leaf spots that are not diagnostic from visualsymptoms. Pestalotia is often seen in the early spring on winter stressed plants. Cercospora,Aschocyta, and Colletotrichum are seen throughout the growing season.

    Pecan crown gall is caused by the bacterial pathogen Rhizobacter tumefaciens(formerly Agrobacterium tumefaciens). The symptoms are large woody galls typicallylocated at the lower trunk area or upper root system. The galls weaken the tree, but do notusually cause death unless the tree is small and/or damaged by additional factors. Thisbacterium has a huge host range. It may remain viable in the soil for 3-4 years. See DiseaseNote 944 for more information.

    Table 1. 2005 March Diseases Seen In The Auburn Plant Diagnostic Lab.

    Plant Disease County

    Bermuda Rhizoctonia Blight *

    Root-knot Nematode (Meloidogyne) *

    Blackberry Cane & Leaf Rust (Kuchneola uredinis) Cullman

    Camellia Algal Leaf Spot (Cephaleuros) Baldwin

    Carex Colletotrichum Leaf Blight *

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    Plant Disease County

    Centipede Brown Patch (Rhizoctonia) Houston

    Collard Black Rot (Xanthomonas) Lowndes

    Daylily Rhizoctonia Crown, Root & Tuber Rot *

    Holly Pestalotiopsis Leaf Spot Cleburne

    Impatiens Bacterial Leaf Edge Spots *

    Jasmine, Asian Pestalotia Leaf Spot Baldwin

    Muscadine Sooty Mold Marshall

    Oak, Sawtooth Seedling Pythium Root Rot Bullock

    Oats Rust (Puccinia sp.) Baldwin

    Palm Pestalotia Leaf Spot Coffee

    Pecan Crown Gall (Rhizobium tumefaciens) Butler

    Plum Black Knot (Plowrightia morbosum) Covington

    Rhododendron Ascochyta Leaf Spot Pike

    Pestalotia Leaf Spot Lee

    Wheat Powdery Mildew (Erysiphe sp.) Lee *Counties are not reported for nursery, greenhouse, and golf course samples.

    Birmingham Plant Disease Report-March (J. Jacobi)

    We received 49 samples in March. Some of the problems diseases last monthincluded algal leaf spot on camellia, large patch on centipedegrass and St. Augustinegrass,eriophyid mites on rosemary, and crown gall on rose.

    High levels of eriophyid mites were found on a recent rosemary sample. The leaves

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    were discolored, twisted and stunted. The undersides of the leaves showed abundant eggsand the tiny worm or carrot shaped translucent mites. The mites are hard to see even with agood hand lens. Several insecticides can be used to control eriophyid mites including: horticultural oil, insecticidal soap, and carbaryl (Sevin). Check the label to make sure thatthe host and eriophyid mites are both listed. Products labeled for spider mites may not killeriophyid mites.

    Large patch of warm season grasses has been very common so far this spring. Thisdisease occurs typically during spring and fall when the turfgrass is entering or existingdormancy. Patches are usually circular and range from 3 ft. to more than 20 ft. in diameter. Look for water-soaked, reddish brown to black lesions on the leaf sheaths. Leaf blades mayhave a yellow-orange color at the edge of patches with active infections. Often patches willshow up in the same area each year. Heritage (azoxystrobin) and Prostar (flutolanil) havethe best control in University trials. For more information on this disease check out thefollowing web site (http://www.aces.edu/pubs/docs/A/ANR-0492/ANR-0492.pdf).

    Table 2. 2005 March Problems Seen In The Birmingham Plant Diagnostic Lab.

    Plant Problem County

    Boxwood, Common Boxwood Leaf Miners Jefferson

    Boxwood Mites Jefferson

    Cottony Cushion Scale Jefferson

    Macrophoma Blight Jefferson

    Camellia Algal Leaf Spot Calhoun

    Centipede Large Patch (Rhizoctonia) Tuscaloosa

    Ivy, English Anthracnose Shelby

    Nandina Planted Too Deep Calhoun

    Orchid Longtailed Mealy Bugs Jefferson

    Petunia High Media pH/Iron Chlorosis *

    Rose Crown Gall (Agrobacterium) Jefferson

    Rosemary Eriophyd Mites Jefferson

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    Ryegrass, Perennial Brown Patch (Rhizoctonia) Jefferson

    Spider Plant Brown Soft Scale Jefferson

    Plant Problem County

    St. Augustinegrass Large Patch (Rhizoctonia) Jefferson

    Tomato High Media Soluble Salts Shelby *Counties are not reported for nursery, greenhouse, and golf course samples.

    March Insect Report (C. Ray)

    COUNTY CROP CATEGORY SPECIMEN NAME

    Jefferson Stored Products Dog Food Mold Mite

    Jefferson Stored Products Dog Food Mold Mite

    Jefferson Medical Home Moth Flies, Dermestid Larvae

    Choctaw Small Fruit Peach White Peach Scale and SanJose Scale

    Pike Structural Old Wood House Unicorn Beetle Larva

    Montgomery Household-Miscellaneous

    Home A Birds Nest Moth

    Lee Ornamental Pyracantha Woolly Apple Aphid

    Jefferson Ornamental Boxwood Cottony Cushion Scale

    Jefferson Ornamental Bradford Pear Ash Whitefly-NEW STATERECORD

    Coffee Household-Miscellaneous

    Home Stable Fly and Housefly Mite

    DeKalb Not Available Not Available Boxelder Bug

    Houston Ornamental River Birch Witch Hazel Woolly Aphid

    Cleburne Ornamental Holly Tetraclia Whiteflies-NEWSTATE RECORD

  • COUNTY CROP CATEGORY SPECIMEN NAME

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    Houston Ornamental Leyland Cypress Maskell Scale and TarsonemidMites

    Mobile Forage Crops Crimson Clover Spider Mites (2) and aTarsonemid Mite

    Lee Household-Miscellaneous

    Home House Clover Mites

    Elmore Household-Structural

    Home Florida Carpenter Ant

    Mobile Ornamental Maple Clearwing Borer

    Coffee Ornamental Christmas Palm Spider Mites

    Disease Possibilities For April

    The list below includes some common disease problems received in the lab during Aprilof the past few years. Comments on control practices are brief. Refer to fact sheets, timelyinformation sheets, and the Alabama Pest Management Handbook for details. Samplesreceived in early April contained several turf grasses with brown patch.

    Table 3. Brief Disease Descriptions and Control Recommendations for Diseases Often Seen in April.

    Plant Disease Description Control

    Many Ornamentals Powdery Mildew White-buff colored,

    raised dots or pads of

    mycelium.

    Fungicides; See Cir.

    ANR-407.

    Aglaonema Bacterial Leaf Spot Circular-angular,

    dark, water-soaked

    leaf spots.

    Sanitation. Water at

    pot level.

    Alfalfa Spring Black Stem

    and Leaf Spot

    (Phoma)

    Small black spots on

    leaves, petioles,

    stems. Stems may

    be girdled.

    Early cutting.

    Leptosphaerulina

    Leaf Spot

    Small black spots on

    leaves and petioles.

    Lesions may enlarge

    to oval-round (1-3

    mm diam), light

    brown spots with

    dark brown borders.

    Yellow areas may

    surround the spots.

    When conditions are

    humid, spots may

    coalesce.

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