JANUARY PLANT PROBLEM REPORT FROM THE AUBURN PLANT DIAGNOSTIC LAB JANUARY PLANT PROBLEM REPORT FROM THE BIRMINGHAM PLANT DIAGNOSTIC LAB

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1 February 12, 2003 PP-543 JANUARY PLANT PROBLEM REPORT FROM THE AUBURN PLANT DIAGNOSTIC LAB JANUARY PLANT PROBLEM REPORT FROM THE BIRMINGHAM PLANT DIAGNOSTIC LAB DISEASE POSSIBILITIES FOR FEBRUARY Jackie Mullen Extension Plant Pathology Specialist Jim Jacobi Extension Plant Pathology Specialist Auburn Plant Disease Report-January (J. Mullen) Of the 23 plant samples received in the lab in January, seven were biological, infectious diseases. The other samples were abiotic problems involving situations of too wet soil, nutrition, or unknown problem situations. Some of our January samples were dead landscape shrubs which could not be diagnosed due to their condition. Old lace bug damage was observed on a couple of azalea samples. The most interesting sample received was a yellow poplar seedling sample with Cylindrocladium crown rot. Diagnosis was made by fungal isolation and identification in culture. This was an interesting sample because we do not see Cylindrocladium crown rot very often. Cylindrocladium is a wellrecognized crown and root rot disease agent on a number of plants. Our laboratory study indicates that the pathogen is probably C. clavatum which has been reported to cause crown rot disease on rhododendron, some pine species, Norfolk Island pine, bottlebrush, Jerusalem thorn, bird-of-paradise flower, and a few other tropical plants. The Alternaria and Cercospora leaf spot disease on cabbage and turnips, respectively, are fairly common problems on crucifers, and we do see these diseases on crucifers during winter from southern most sections of the state. See the Alabama Pest Management Handbook for disease

2 control recommendations. The bacterial soft rot developed secondarily in the previously damaged tissues. Irish potatoes were observed with Fusarium rot and secondary bacterial soft rot and Rhizopus Rot. We suspect the initial damage was caused by the Fusarium. Both the Fusarium, bacteria, and Rhizopus usually enter the plant tubers through wounds. Disease control recommendations include (1) careful handling to avoid wounding, (2) high humidity and good ventilation during storage, (3) seed tuber treatment with fungicide before storage, (4) warming seed tubers for a week at C before planting, (5) planting seed immediately after cutting in warm, moist soil which promotes good sprout development and good wound healing, (6) spraying or dipping seed tubers with fungicide before planting, and (7) handling treated seed with clean containers and equipment. Reports indicate that good sprouts and plants may develop from tubers showing low levels of Fusarium rot if temperatures are warm enough to encourage rapid sprout growth. Cool weather will favor good Fusarium growth and slow sprout growth. Bacterial soft rot and Rhizopus rot develop when conditions are warm and moist. The tea olive (Osmanthus fragrans) was observed to have large, irregular, brown leaf spots. Culture work produced the fungus Colletotrichum which is reported to cause anthracnose on tea olive. The control recommendation for anthracnose on ornamentals typically involves sanitation and protective sprays of Cleary s 3336 or Halt. Wheat was observed with a yellowing dieback, where discoloration begins at the leaf tips and progresses downward into the plant. At this time of year, it is difficult to determine whether the yellowing damage is nutrient related, a virus such as barley yellow dwarf virus, or some other problem. ELISA tests at this time of year (December-March) often produce false negative results due to a low titer (concentration) of virus in the plant. Nutrient analysis can sometimes help resolve the question of barley yellow dwarf virus. The yarrow with Pythium root rot showed a slight indication of leaf tip scorch and about 40-50% root discoloration and decay. Culture work and ELISA tests indicated that Pythium root rot was present. Pythium often develops as a root rot problem after a previous stress or injury such as drought or excess fertilizer salts. Disease management involves removal of damaged plants, reduction of irrigation (if appropriate), and application of protective fungicide drenches. Subdue will control Pythium, and the Subdue label allows for ornamentals use after testing on a small group of plants. A Japanese holly plant that showed root decay and crown rot was received. Crown sections were placed in culture and all 15 crown isolations produced Sclerotium rolfsii. This fungus has an extremely wide host range on herbaceous and woody crops. Damaged plants should be removed along with rootassociated soil. After plant removal, the soil should be turned deeply so as to bury crop debris along with the associated fungus. Wider plant spacing will help increase air movement and decrease disease. Solarization (see ANR-713) will help reduce fungus levels in the soil or fumigation (applied by a certified applicator) may be used to reduce fungus levels in the soil. Terraclor products or Heritage may be applied as protective drench treatments at transplanting, usually in greenhouse situations. Sclerotium rolfsii develops and causes diseases in Alabama when temperatures are at 85 F or above and moisture levels are high. Usually S. rolfsii is a problem in Alabama during June-August. The fungus survives the winter in the soil as sclerotia-hard, round, brown or black spherical bodies about the size of mustard seeds. See ANR- 2

3 1157 for more information. Table January Diseases Seen In The Auburn Plant Diagnostic Lab. Plant Disease County Cabbage Alternaria brassicicola Leaf Spot Baldwin Bacterial Soft Rot Baldwin Holly, Japanese Sclerotium rolfsii Crown Rot Autauga Irish Potatoes Bacterial Soft Rot Baldwin Fusarium Rot Rhizopus Rot Baldwin Baldwin Olive, Tea Colletotrichum Leaf Spot Russell Poplar, Yellow Cylindrocladium clavatum Crown Rot * Turnips Cercospora Leaf Spot Bibb Wheat Possible (Suspect) BYDV Autauga Yarrow Pythium Root Rot * *Counties are not reported for greenhouse and samples. Birmingham Plant Disease Report-January (J. Jacobi) The lab received 32 samples for the month. The cold weather was one of the biggest stories during the month of January. Average monthly temperatures were 4.2 F below normal. Many marginally hardy plants were injured when temperatures reached 7 F on January 24 th. Some of the fragrant tea olive plants at the botanical gardens were nearly defoliated by the cold weather. Some of the other problems seen last month included azalea bark scale, Pythium and Black root rot of pansy, and Alternaria leaf spot on pittosporum. Alternaria leaf spot was found on leaves of pittosporum. The spots are small necrotic lesions surrounded by yellow halos. Control of this disease involves maintaining shrubs in good growing condition and applications of a protective fungicide (azoxystrobin, iprodione and others) in some cases. Do not use chlorothalonil (Daconil) sprays on pittosporum. Homeowners have few fungicide choices for control of this 3

4 disease. The black twig borer (Xylosandrus compactus) has been found in samples of Southern magnolia and red maple this winter. This ambrosia beetle attacks apparently healthy twigs of living broadleaved trees and shrubs. The first signs of infestation are terminals, twigs and small branches with fading, wilting, and browning foliage scattered throughout the crown (Solomon, 1995). As many as 50 branches have been affected on one large magnolia tree. Close inspection of damaged branches shows small pin-sized holes, usually on the underside of the branches. Cutting open affected twigs reveals the brood chamber, which is filled with very small (1/16 in.) beetles, along with other stages of the insect. Attacked twigs usually die or cankers develop along them. Control measures include: pruning out damaged branches, fertilizing and watering trees to keep them healthy and vigorous to reduce susceptibility to attack, and insecticide sprays. For more information on this pest refer to the following web site: Table January Problems Seen in the Birmingham Plant Diagnostic Lab. Plant Problem County Azalea Azalea Bark Scale/Sooty Mold Jefferson (2) Boxwood, Common Boxwood Leafminer Jefferson (2) Low ph/pythium Root Rot Winter Injury Jefferson Jefferson Holly, Japanese Pythium Root Rot Jefferson Magnolia, Southern Black Twig Borer (Xylosandrus compactus) Jefferson Pansy Black Root Rot (Thielaviopsis) Jefferson (2) Pythium Root Rot Jefferson Pittosporum Alternaria Leaf Spot Jefferson Rose Chemical Injury Jefferson Tomato (Greenhouse) Whiteflies (Bemesia sp.) Jefferson Wax Myrtle Botryosphaeria Canker Jefferson 4

5 Disease Possibilities For February Powdery mildews and Botrytis may be a problem in greenhouses where temperatures are on the moderate to cool side. Also downy mildew (yellow spotting, sometimes defoliation) on rose and bedding plants and vegetable transplants may develop when temperatures are moderately cool (60-70 F). Powdery mildew disease spread requires a high relative humidity. Botrytis and downy mildew require high relative humidity and free moisture for disease spread. If temperatures are F, some leaf spots on grasses may develop. The list below includes some common disease problems received in the lab in February of the past few years. Comments on control practices are brief. Refer to appropriate fact sheets, or timely information sheets for details of disease control. Table 1. Disease Descriptions and Brief Control Comments on Some Common Diseases Often Seen in February. Aglaonema Rhizoctonia Crown Rot Brown dry decay of lower stem. Sanitation; Cleary's 3336 protective treatments. Alfalfa Spring Black Stem and Leaf Spot (Phoma) Numerous black spots on lower leaves, petioles, and stems. Leaf spots often coalesce and become medium or light brown. Spotted leaves become yellow and fall. Lesions may completely girdle stems and petioles and cause death to the foliage beyond. Phoma may also cause a crown and root rot. -- Arbor-vitae Cold Damage/ Pestalotiopsis Tip Blight Tips show some dieback which eventually becomes gray colored. Spring pruning to remove the dead plant parts. Azalea Cercospora Leaf Spot Brown, roughly circular leaf spots, diameter. Sanitation; See the Ala. Pest Management 5

6 Begonia Botrytis Blight Brown, water-soaked or dry tissue blight. See the Ala. Pest Management Bentgrass Brown Patch (Rhizoctonia) Irregular foliage leaf spots and blight; irregular brown patches in lawn. See the AL Pest Management Pythium Blight Quickly spreading, brown blight (wetlooking) or grass blades. See AL Pest Management Pythium Root Rot Roots become brown and water-soaked and then dry. See the Ala. Pest Manage-ment Bermuda Helminthosporium Spots Brown elliptical or elongated rectangular, usually small (but spot coalescence often occurs) leaf spots. Sometimes decay occurs at the stem near the soil line and then whole plants die rapidly. Often, spots remain localized on the leaves. See ANR-621. Rhizoctonia Blight Slime Mold Patchy areas become brown. Individual leaves show brown spots, larger blotches, or a complete leaf blight. Thin, translucent, rumpled sheets of gelatin-like material. See ANR-492 or the AL Pest Management Physical removal. 6

7 Boxwood Macrophoma Blight Foliage becomes off color (usually yellow but may be bronzed) and tiny black dots (fruiting bodies) develop on leaves and sometimes small twigs. Phytophthora Crown & Root Rot Lower trunk is brown and rotted. Initially the decayed tissues are water-soaked but later the dead tissues are dried. Maintain plants in good health and avoid stressful conditions. Protective fungicide treatment may not be needed but if desired, see AL Pest Management Improve soil drainage and/or decrease irrigation. See Alabama Pest Management Handbook for fungicides recommended for nursery situations & some large scale landscape plantings. Broccoli Downy Mildew (Peronospora) Camellia Algal Leaf Spot (Cephaleuros) Anthracnose (Colletotrichum) Faded, yellow blotches on upper leaf surfaces show gray, powdery masses of fungal growth on lower leaf surfaces in areas corresponding to yellow spots. Reddish-green or reddish-brown roundish leaf spots with a slightly raised edge develop. Light to medium brown, circular-irregular (0.2-1 cm diam.) spots develop on leaves. Reduce humidity; raise temperatures; see Ala. Pest Management Prune to reduce humidity levels. Protective treatments of Bordeaux mixture may be used. See the AL Pest Management Sanitation; Protective fungicides labelled on camellia such as Cleary's

8 Botrytis (Sclerotinia) Flower Blight Brown, small-large, irregularly-shaped lesions. Sanitation of fallen blossoms; see Ala. Pest Management Ring Spot Virus Yellow rings appear on foliage; plants may become slightly stunted. Carolina Cherry Laurel Blumeriella jaapii, Roundish, brown leaf spots with a slightly darker edge develop on leaves. Cleary s 3336 or Halt may provide some protection. Collard Black Rot (Xanthomonas) Yellow, V-shaped lesions on leaf edges become darkened. Bacteria spread into the vascular system and cause leaf veins to darken. Eventually, tissue death and decay spreads into the central vascular system with the lower center stalk becoming rotted. Crop rotation away from crucifers for 2 years. Daylily Kabatiella Leaf Spot Red brown elongated spots (approx. c-¼ inch diam.). Dusty Miller Alternaria Leaf Spot Dark brown angular spots ( cm) on foliage. Cleary's 3336 may help. English, Ivy Anthracnose (Colletotrichum) Circular or irregular, dry, brown spots or blotches on leaves. Leaf spots often begin at leaf edges. Brown stem lesions may also develop. See the AL Pest Management Handbook or ANR

9 Euonymus Anthracnose (Colletotrichum) Large (¼-½ inch diam.; cm) brown, circular spots. See Ala. Pest Management Fescue Pythium Foliage Blight Dark, water-soaked spots and blotches. See Ala. Pest Management Scab (Elsinoe) Brown, raised, slightly corky spots ( cm) develop on foliage. Sanitation; Cleary's 3336 may help. Geranium Oedema Small ( cm diam.), raised corky spots scattered on lower leaf surfaces. Upper leaf surfaces corresponding to corky spots often show yellowed spots. Reduce watering schedules when weather is cloudy and cool. Gerbera Daisy Powdery Mildew Leaves show some necrosis and white powdery dusting on leaf surfaces. Sanitation; Cleary's Pythium Root Rot Plants become stunted and yellowed. Usually lower leaves become yellowed first. Roots become brown and water- soaked. Sanitation of damaged plants. In some situations, removal of contaminated soil or media is recom-mended. Protective fungicide drenches in greenhouse situations. 9

10 Greenhouse/Nursery Crops Peat Mold (Chromelosporium) Tan-orange-yellow spore masses often develop on the surface of potting mix or at the edge of potting mix next to the pot rim. Extensive fungal growth may cause the potting media to become water repellent; that is, the media will not absorb water. Holly, Foster Bacterial Leaf Spot Small, black, angular leaf spots. Holly, Japanese Phomopsis Dieback Cankers on twigs and small branches with dieback resulting. Hydrangea Powdery Mildew White dusty coating on upper leaf surfaces. Leaf yellowing and blight; some new growth distortions. Fungicide spray treatments. See AL Pest Management Phytophthora Pythium Root Rot & Roots brown and watersoaked initially, then dried. Sanitation; improve soil drainage and/or reduce irrigation; Banrot or Banol are recommended in some nursery situations. Impatiens Impatiens Necrotic Spot Virus Black, circular leaf spots; stunted growth. Sanitation; control. thrips 10

11 Phytophthora Rot Crown Plants become stunted. Older leaves turn yellow. Roots become brown and watersoaked. Sanitation of plants and sometimes removal of contaminated soil or media. Adjust watering practices and/or improve water drainage through soil or media. Fungicide drenches are often recommended in greenhouse situations. Pythium Crown Rot See Phytophthora comments. See Phytophthora comments. Impatiens, New Guinea Botrytis Stem Rot Dark, water-soaked leaf blight & stem rot. Sanitation; See Ala. Pest Management Impatiens Necrotic Spot Virus New growth is stunted; circular black, greasy spots develop. Remove damaged plants; control thrips. Tomato Spotted Wilt Virus Damage is identical to impatiens necrotic spot virus. Remove damaged plants; control thrips. Indian Hawthorn Cercospora Leaf Spot Circular, dark brown spots (approx. c inch diam.) Sanitation; Mancozeb fungicide. Entomosporium Spot Leaf Red-black spots. See the Ala. Pest Management Suspect Bacterial Leaf Spot Red-black spots. angular Irish Potato Scab (Streptomyces Slightly raised, rough, Crop rotation. Keep scabies) corky, cortex-colored soil ph at , if spots, lesions (smalllarge) possible. on tubers. Scurf (Rhizoctonia) Black, irregular, hard slightly raised roughsurfaced scabs on tuber surface. 11

12 Crop rotation. Terraclor. See E. Sikora. Ivy, English Anthracnose (Colletotrichum) Black irregularly shaped leaf spots. Sanitation; See AL Pest Management Bacterial Leaf Spot (Xanthomonas) Brown-black, angular, wet-looking spots (c- ¼ inch diam.; cm). Sanitation; See Ala. Pest Management Ivy Leaf Geranium Oedema Upper leaf surface shows diffuse yellow spots; lower leaf surface shows brown, corky, slightly raised spots (less than c inch diam.; cm). Decrease schedule. watering Kalanchoe Botrytis Blight Brown, gray spots, blotches on the foliage. Infected areas may become limp. Spots look grayer when spore production occurs. Apply protective fungicide drenches. See the Ala. Pest Management Decrease humidity. Increase temperature. Lantana Foliar Leaf Spot Nematode Angular, leaf spots. brown-black Leyland Cypress Seiridium Canker Elongated, sunken lesions with sticky sap running down the bark. Pruning. Maintain good tree vigor. See AL Pest Management Lily, Easter Lily Symptomless Virus & Cucumber Mosaic Virus Yellow and brown flecks on foliage; plants stunted; leaves curl under. aphids. Control Magnolia Algal Leaf Spot (Cephaleuros) Greenish or reddish 12

13 slightly raised spots (0.1-1 cm) on upper leaf surfaces. Spot edges are often irregular or wavy in appearance. Old spots are usually cream colored in the center. Control measures are usually not necessary. Bordeaux mixture may be used. See the Ala. Pest Management. Marigold Botrytis Canker Dark brown, elongated cankers form on stems. See the AL Pest Management Oats Helminthosporium Leaf Spot/Blotch On seedlings, oblong to elongate, light-reddishbrown spots appear on seedling leaves. Seedling leaves may also be twisted. On older leaves, spots start as small, brown flecks that develop into longitudinal flecks of dead tissue. Tissue outside of the leaf spot become brown, yellow or red. Sometimes these discolored areas around the spots spread to involve the major portion of the leaf blade. See the Small Grains Recommendations for seed treatment; rotate crops; plow under residue. Crown Rust (Puccinia coronata) Orange-colored pustules form on leaves, mainly; severely infected plants will turn yellow and grow poorly. Contact A. Hagan. Pansy Botrytis After Cold Brown leaf spots/ Sanitation; protective Damage blight; gray mold. fungicide sprays. See AL Pest Management Cercospora Leaf Spot Brown-black circular spots. Sanitation; Cleary's 13

14 Phytophthora Crown/Root Rot See comments for Impatiens. Pythium Rot Crown/Root See comments for Impatiens. Peach Botryosphaeria Canker (Gummosis) Gummy, "bleeding" or oozing spots of sap develop on bark surfaces where sunken, darkened lesions occur in the wood. Lesions are often cracked around the edge. Sanitation; Benlate sprays on the trunk. Cytospora Canker Sunken lesions on branches and trunk. Prune off lesions making cuts 3-4 inches beyond margin of decay. Phomopsis Twig Blight Gray sunken cankers, dieback. Check with Ed Sikora. Peas, Austin Sclerotinia Blight A dark wet-looking rot develops at lower stem area near soil. A white fungal mat may develop. Small (1/16 inch or less) black, hard, flat, irregular- shape bodies may develop in the fungal mat. Infected plants wilt and die. Pentas Bacterial Leaf Spot Dark brown, angular leaf spots, 1/16-1/8 inch diam. Crop rotation. Photinia Entomosporium Leaf Spot Small reddish spots (¼- ½ inch diam.; cm) often coalesce into larger red spots with dark red centers and bright red, diffuse borders. 14

15 Sanitation; See the Ala. Pest Management Pine, Loblolly Needle Rust (Coleosporium) Cream-white pustules (c inch diam.; cm) on needles. No control recommended. Pine Seedlings, Loblolly Phytophthora Root Rot Plants become stunted. Older growth becomes yellowed. Roots become brown and water-soaked. Sanitation of infected plants and sometimes media/soil replace-ment is recommended. Correct water problems. Fungicide drenches are recommended in nursery situations. Pine, Virginia Lophodermium (Ploioderma) Needle Cast Small (1/32-1/16 inch diam.; 0.15 cm or less; just barely visible), black, football-shaped slightly raised fruiting bodies scattered on needles; needles brown and drop. See Ala. Pest Management Poa trivialis Pythium Blight Foliage blight. Decrease water content of soil. Apply fungicide treatments as listed in the Alabama Pest Management Handbook for turf grasses. Pothos Rhizoctonia Stem Rot Stems near or touching the soil (potting mix) developed a dark brown canker or lesion (0.3-1 cm). Protective sprays of Cleary's Rhododendron Botryosphaeria Canker Elongated, sunken cankers with cracked edges. Pruning and sanitation. Rosemary Pythium Root Rot Roots become brown and soft rotted. 15

16 Ryegrass Pythium Root Rot Grass turns yellow, withers and dies; roots show a wet, brown decay. See the Ala. Pest Management Handbook or ANR-594. Take-All Patch Individual plants become yellow and die. Roots develop dead areas and lesions. Affected plants are usually in patchy areas of landscape. Manage soil ph and nitrogen appropriately. Apply fungicide treatment when economically feasible. See ANR-823. St. Augustine Brown Patch (Rhizoctonia) Irregular areas become brown due to browning of individual grass blades. See the Ala. Pest Management Handbook or ANR-492. Take-All Patch ( Gaeumannomyces graminis graminis) See comments under Ryegrass. Snapdragon Root-Knot Nematode (Meloidogyne) Stunted, wilted plants; roots develop irregular galls. Sanitation; See AL Pest Management Spinach Pythium Root Rot Plants are stunted; roots develop a light brown discoloration; roots pull apart easily. Sanitation; reduce moisture levels in the soil. Spirea Powdery Mildew Leaves show a white powdery dusting on upper leaf surfaces and young shoots Cleary's Strawberry Common Leaf Spot (Mycosphaerella) Red to red-black leaf spots. Sanitation; See AL Pest Management Pythium Root Rot Roots brown and watersoaked. See E. Sikora. Tomato Bacterial Leaf Speck Very small (1/16 inch diam.) angular, dark brown spots often with a diffuse yellow halo. See AL Pest Management 16

17 Turnip Cercospora Leaf Spot Small, off-white, irregular spots which may enlarge into ¼-½ inch diam. ( cm). Verbena Bacterial Leaf Spot Angular, water-soaked black or dark green leaf spots. See AL Pest Management Myrothecium Rot Crown Plants collapse after decay at crown. Foliar Nematode Angular brown leaf spots; sometimes these symptoms can be confused with bacterial disease. Pythium Root Rot Roots brown and watersoaked when infections are new. Sanitation; improve water/soil situation so soil does not remain wet. Wheat Bipolaris Leaf Spot Brown elongated lesions (typically c-¼ inch long) on foliage. -- Powdery (Erysiphe) Mildew A white to light brown (buff) dusting or slightly raised powdery patches on foliage. Affected leaf areas eventually turn yellow and die. Infection of the flag leaf will severely affect plant development and yield. See the Ala. Pest Management Handbook and/or A. Hagan. Soilborne Mosaic (SBWMV) Wheat Virus Green-yellow mosaic pattern (short, narrow stripes) on leaves; stunting; reduced tillering; possible plant death. Crop rotation. 17

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