march plant diseases from the auburn - aces. · pdf fileextension plant pathology, extension...

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

April 17, 2001 PP-503

MARCH PLANT DISEASES FROM THEAUBURN PLANT DIAGNOSTIC LAB

MARCH PLANT DISEASES FROM THEBIRMINGHAM PLANT DIAGNOSTIC LAB

DISEASE POSSIBILITIES FOR APRIL

ANNUAL REPORT OF THE ACES PLANT DIAGNOSTIC LABS

Jackie Mullen ([email protected])Extension Plant Pathology Specialist-Auburn

Jim Jacobi ([email protected])Extension Plant Pathology Specialist-Birmingham

Auburn Plant Disease Report-March (J. Mullen)

We can definitely tell that spring is here in the lab with our increased sample numbers! Botrytis, brownpatch on centipede, tomato spotted wilt virus, and the usual spring leaf spot problems were seen last month.

Brown patch on centipede seems to be well established in the southern sections of the state. Samples seenin the lab have had abundant microscopic mycelial growth on the lower leaves and stolons with accompanying leaf-stolon blight. Several fungicides are labeled for control of brown patch on turf. It is also important to keep nitrogenfertilization at a low-normal levels, collect clippings and irrigate early in the day. See ANR-492.

Botrytis blight has been seen as a problem on greenhouse rosemary, lavender, and geranium. Also, werecently saw it causing a blossom blight on dogwood. In a greenhouse, Botrytis is controlled by reducing humiditylevels, sanitation, and protective fungicide sprays. Several fungicides will control Botrytis. See the 2001 AlabamaPest Management Handbook.

mailto:[email protected]

mailto:[email protected]

Tomato spotted wilt virus was confirmed on Gomphrena globosa. New growth showedunusual patterns of yellow spots. Thrips were also present. This can be a difficult disease to control. Sanitation and thrips control is important.

Pestalotia leaf spots were seen on azalea, gardenia, holly, and rhododendron. Pestalotiausually causes damage on plants in the early spring following cold damage or other stress situations. This fungus is not often a problem later in the spring, summer, or fall.

Other fungal leaf spot diseases seen included Botryosphaeria and Colletotrichum on hollyand Colletotrichum on pepper.

Botryosphaeria canker was noted on oak; Botryosphaeria often causes cankers on stressedor previously damaged trees and shrubs. It is a fairly common occurrence in the spring after colddamage.

Pythium blight was noted as an unusual occurrence on annual periwinkle and Torenia. Webelieve this fungal damage followed after injury from excess fertilizer salts.

Table 1. 2001 March Diseases Seen In The Auburn Plant Diagnostic Lab.

Plant Disease County

Azalea Pestalotia Leaf Spot Marion

Begonia Pythium Blight *

Centipede Brown Patch (Rhizoctonia) Covington, Elmore,

Tallapoosa

Daffodil Fusarium Basal Bulb Rot Calhoun

Daylily Pythium Crown & Root Rot Pike

Gardenia Pestalotia Leaf Spot Lee

Geranium Botrytis Blight Lee

Gomphrena Tomato Spotted Wilt Virus *

Holly Botrytosphaeria Leaf Spot Covington

Colletotrichum Leaf Spot Covington

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Pestalotia Leaf Spot Marion

Lavender Botrytis Blight *

Million Belles Pythium Root Rot *

Myrica Cuttings Fusarium Cutting End Rot *

Oak Botryosphaeria Canker Lee

Pepper Colletotrichum Leaf Spot *

Periwinkle, Annual Pythium Blight *

Rhododendron Pestalotia Leaf Spot Marion

Rosemary Botrytis Blight *

Pythium Root Rot *

Ryegrass Pythium Blight Lee

Snapdragon Colletotrichum Leaf Spot Lee

Pythium irregulare Crown & Root Rot Out-of-State

Tomato Colletotrichum Leaf Spot *

Torenia Pythium Blight * *Counties are not reported for greenhouse and nursery samples.

Birmingham Plant Disease Report-March (J. Jacobi)

The first days of spring were cooler and wetter than normal, providing good conditions forcertain diseases and an increase in samples received at the lab. We continued to see damage fromcold and drought on a wide range of plants including azalea, juniper, rose, and turfgrass. The effectsof last summer’s severe drought are and will continue to produce dieback and other related problems. Cold damage to Orchid (Phalaenopsis spp.) was seen last month. Symptoms are yellow depressedstreaks on the leaves that eventually turn tan and then black and become pitted. The streaking ismost prominent along the margins of the leaves. Exposure to cold temperatures

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(as little as 45°F for two hours on young leaves) or cold water that condenses and falls on newlydeveloping leaves causes the problem. Symptoms show up about six weeks after the coldtemperatures. This was a new problem for the lab and was identified with the help of another plantpathologist. Other unique samples seen during March included crown gall on apple and Armillariaroot rot on peach. See ANR-944 and ANR-907 for more information on crown gall and Armillariaroot rot, respectively.

Mulches and composts have many beneficial side effects including improving soils,conserving moisture, and controlling weeds. However, uncomposted or fresh materials comprisedprimarily of wood with little bark can result in the development of detrimental and nuisance fungiincluding different types of mushrooms and slime molds. Last month, a columned stinkhorn(Linderia columnata) was brought into the lab– and immediately taken back outside. This and otherstinkhorns have a foul odor similar to rotting meat. In this case, the fungus colonized a landscapebed mulched with one of the colored mulches (largely uncomposted wood product with little bark). In addition, some of the mushroom (fungi) that colonize mulch are toxic and should be destroyedwhen small children have access to the area. Once these fungi have colonized the mulch there maybe little that can be done. Removal or spading the affected mulch into the soil and wetting the areamay provide some level of control. The best strategy is to purchase composted products low in woodcontent and prevent a potential problem. Additional information on nuisance and detrimental moldsin mulches and composts can be obtained at the following site: http://www.ag.ohio-state.edu/~ohioline/hyg-fact/3000/3304.html.

Table 2. 2001 March Diseases Seen In The Birmingham Plant Diagnostic Lab.


Apple Crown Gall (Agrobacterium tumefaciens) *

Azalea Lace Bugs Jefferson

Boxwood Boxwood Leafminer Jefferson

Macrophoma Leaf Spot Jefferson

Macrophoma Leaf Spot and Pythium Root Rot Jefferson

Centipede Brown Patch Shelby

Evergreen Clematis Pythium Root Rot St. Clair

Orchid Cold Injury Jefferson

http://www.ag.ohio-state.edu/~ohioline/hyg-fact/3000/3304.html

http://www.ag.ohio-state.edu/~ohioline/hyg-fact/3000/3304.html

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Peach Armillaria Root Rot Shelby

Photinia Entomosporium Leaf Spot Jefferson

St. Augustinegrass May/June Beetle Grubs Jefferson *Counties are not reported for greenhouse and nursery samples.

Disease Possibilities For April

April diseases are abundant, and a long list of possibilities for reference purposes is includedbelow.

Rust diseases were not very noticeable in March, but we will see them in April. With fusiformerust on loblolly and slash pine, the rusty spores will cover the fusiforme swellings that develop onbranches and trunks. These spores are wind-carried to oaks where infections occur on the leaves. Tiny black leaf spots on the oak will produce orange spores on lower leaf surfaces March-May. These spores are wind-carried and will cause infection of the loblolly and slash pine. Once infectionoccurs on the pine needles/twigs, 2-3 years may pass before mature, spore-producing galls arepresent. Disease control is difficult. In a nursery situation, fungicides are recommended forprotective control. (See the Alabama Pest Management Handbook.) In a landscape, usuallysanitation is the only practical recommendation. Watch for other rust diseases in April. Cedar-applerust (also, cedar-quince or cedar-hawthorn rusts) will probably appear in April this year.

Peach leaf curl, caused by the fungus Taphrina, is easily recognized by the curling, distortion,and swelling it causes on infected leaves. Spores produced in the spring are carried by wind and rainto near-by peach trees where they fall onto the bark areas of twigs and branches. These spores willover-winter in protective niches in the bark. In the spring the spores may be moved by wind and rainso that they infect new leaves as they emerge and develop. For control, a dormant fungicidetreatment is applied once (see the Ala. Pest Management Handbook) in the fall after leaf drop or inthe spring before budswell.

Phomopsis canker has been a problem on peach the last few years. It usually develops in April. Typical cankers develop on twigs and small branches as elliptical gray sunken lesions. Lesions willenlarge, and foliage wilt and dieback will result. Check with Ed Sikora for more information.

Dogwood anthracnose is present in Alabama and has been identified in wooded (mostly statepark) areas at elevations of 600 ft. and higher in the northern and northeastern sections of thestate. The disease first appears as a leaf spot (brown irregular spots with purple margins) problem,usually in the lower foliage canopy. If conditions are favorable for disease development (60-70°F

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and wet), leaf spots will spread to involve a leaf blight and eventually a dieback problem. Blightedleaves will typically remain attached to the branches throughout the winter months. Spread of thisdisease is somewhat restricted in Alabama due to high summer temperatures which are notconducive to disease development and spread. To control this disease in the landscape, sanitationand application of protective fungicide sprays are recommended. See ANR-551 for a list offungicides.

Dogwood spot anthracnose is a disease that usually is significant only in that it diminishes thebeauty of the foliage and blossoms. Tiny red or brown spots may cover the bracts and leaves whenweather is wet and warm. When desired, fungicides may be applied for protective disease control. See the Alabama Pest Management Handbook.

Powdery mildews are a problem on a wide variety of plants in the spring when moderatetemperatures and high humidity situations exist. The fungus grows in the upper-most epidermal cellsof leaves and stems. The white powdery coating on leaves and stems is characteristic of the disease. Infected leaves eventually become yellowed, withered and browned. Control involves sanitationand protective fungicide sprays. See ANR-407 for recommended fungicides. Some of the powderymildews are also a problem in the summer.

Oedema, another spring problem on a wide variety of plants, develops when plants are subjectedto cool, cloudy days and prolonged wet soil conditions. Under these conditions, water uptake byplants may greatly exceed water loss in transpiration. As a consequence, some excessively turgidcells in the leaves burst. These burst cells occur in groups on lower leaf surfaces and they appearas small corky spots. Upper leaf surface areas corresponding to the lower leaf surface corky spotsbecome yellow spotted. The only remedy for oedema is a reduced irrigation schedule and improvedsoil drainage. Some woody plants damaged by edema are camellia, Eucalyptus, ivy species, jasmine,ligustrum, schefflera, and Fatsia x Fatshedera. Geranium and related plants are also prone to edemawhen wet, cloudy conditions exist.

Botrytis blight is a common foliage disease when conditions are wet, humid and temperaturesare relatively cool (61-73°F). Flowers, leaves and stems may become covered with brown spots andblotches. When conditions are humid and cool, spore production on the spots causes lesions toappear gray with a fine, delicate, superficial, gray fuzzy layer. Disease control can be achieved bysanitation, raising temperatures, increasing air circulation (reducing humidity) and protectivefungicide treatments.

While temperatures are still cool in the spring, Thielaviopsis black root rot may be a problemon cotton. Infected roots display black spots, lesions. Often root tips are affected. Infected rootsystems are poorly developed and top growth is consequently reduced. Control involves croprotation away from cotton or a Batan seed treatment (1 oz./100 seed wgt). Black root rot may alsooccasionally be a problem on Helleri holly and pansy.

The list below includes some common disease problems received in the lab during April of thepast few years. Comments on control practices are brief. Refer to fact sheets, timely information

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sheets, and the Alabama Pest Management Handbook for details.

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 ofmycelium.

Fungicides; See Cir.ANR-407.

Aglaonema Bacterial Leaf Spot Circular-angular, dark,water-soaked leafspots.

Sanitation. Water atpot level.

Alfalfa Spring Black Stem andLeaf Spot (Phoma)

Small black spots onleaves, petioles, stems. Stems may be girdled.

Early cutting.

Leptosphaerulina LeafSpot

Small black spots onleaves and petioles. Lesions may enlarge tooval-round (1-3 mmdiam), light brownspots with dark brownborders. Yellow areasmay surround thespots. Whenconditions are humid,spots may coalesce.

Frequent harvest.

Stemphyllium LeafSpot

Spots (3-4 mm) areoval, slightly sunken,dark brown with lightcenters. Usually spotsare surrounded by ayellow halo.

Frequent harvesting.

Apple/Pear Botryosphaeria Canker Cankers may be smallor large (up to 5 mlong). Cankers may besuperficial with only aslight roughening ofthe bark or they maybe deep, causingconsiderable cracking.

See Ala. PesticideHandbook; Pruning.

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Fireblight (Erwinia) Blossom blight; leafand branch dieback. Blossoms becomespotted and thencompletely black orbrown. Infectionspreads from theblossoms into twigs,leaves and brancheswith branch cankerdevelopment.

Pruning; Streptomycinat bloom.

Frogeye Leaf Spot(Botryosphaeria)

Small (1/8-1/4 inchdiam.) circular-irregular spots withpurple margins andbrown centers.

Sanitation in the fall;protective spraysduring growing season.

Amaryllis Stagnospora Leaf Spot Dark red blotches onleaves (5-15 mm long.)

Sanitation; Cleary's3336 or Domain.

Azalea Botrytis Petal Blight Large irregular areasof blossoms turnbrown; brown areasare covered with a graydelicate webbingduring humid weather.

See Ala. Pest Manage-ment Handbook.

Exobasidium Gall Swollen blossom, leaf,and shoot galls. Frommid-April to mid-May,galls change from agreen to a white orpink-white color.

Sanitation; removal ofgalls while they arestill green; see the Ala.Pest ManagementHandbook.

Ovulinia Petal Blight Small white-brownspots enlarge to be-come large brownedareas on the blossoms.


Phytophthora Crown &Root Rot

Crowns & rootsbecome brown andwater-soaked.

Sanitation; See Ala.Pest ManagementHandbook.

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Rhizoctonia AerialBlight

Lower leaves becomespotted and eventuallywhole leaves becomedark brown and fall.


Barley Spot Blotch(Bipolaris)

Brown, elongatedspots (2-25 mm long)on leaf blades.

Rotation with non-grass species; fung-icide treated seed; SeeAla. Pest Manage-mentHandbook or sprayguide.

Beans, Butter Alternaria Leaf Spot Gray or dark grayirregularly-shapedspots of variable size.

Sanitation; See theAla. Pest ManagementHandbook underAnthracnose.

Beans, Garden Pythium SeedlingDisease

Lower stems becomewater-soaked, flaccid,and slightly dis-colored. Plants even-tually collapse withstems dry andshrivelled.

Do not over-watergarden or flower bed. See Ala. Pest Manage-ment Handbook.

Fusarium SeedlingBlight

Lower stems and rootsbecome reddish brownand dry rotted.

Sanitation. Croprotation. Resistantvarieties.

Rhizoctonia CrownRot

Brown sunken lesionson the lower stem nearthe soil line.

See the Ala. PestManagement Hand-book. Sanitation.

Bee Balm Powdery Mildew Leaf distortions;powdery white dustypatches on foliageleaves (upper leafsurfaces) and stems.

Sanitation.

Begonia Bacterial Leaf Spot Dark, black, water-soaked spots andblotches.

Strict sanitation. Donot water overhead.

Bentgrass Brown Patch(Rhizoctonia)

Circular-irregularpatches in lawnbecome brown. Brownlesions present onindividual grassblades.

Reduce nitrogenfertilization. Pro-tective fungicidetreatments.

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Pythium Blight Foliage becomes palebrown and water-soaked.

See Ala. PestManagement Hand-book, spray guide.

Bermuda Drechslera Leaf Spot See HelminthosporiumLeaf Spot.

Helminthosporium-type Leaf Spot/Blight(Exserohilum)

Small brown elongatedspots (2-3 mm) whichmay merge and causeleaf blight.

See Ala. PestManagement Hand-book.

Rhizoctonia BrownPatch

See bentgrass. See bentgrass com-ments.

Blackberry Double Blossom(Cercosporella)

Floral canes developabnormal flowers withthickened petals. Internodes areshortened. Leafdevelopment at nodesis abnormallyabundant.

Sanitation as soon asabnormality isdiscovered. Protec-tive fungicide treat-ment; see spray guide.

Orange Rust(Gynoconia)

Young shoots are weakand in clusters. Poorgrowth results fromsystemic disease. Black specks withchlorotic halos developon upper surfaces ofpale green-yellowleaves. Three weekslater, tiny orange,powdery pustulesdevelop on lower leafsurfaces.

Sanitation.

Blueberry Botryosphaeria StemCanker

Somewhat incon-spicuous sunkencankers develop alongbranches or on lowertrunk areas. Diebackresults. (Sometimesthis condition isassociated with soilsexcessive in phos-phorus & calcium.

Sanitation. Benlateprotective sprays. Seethe Ala. Pest Manage-ment Handbook, orspray guide.

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Boxwood Macrophoma Blight(Stress)

Individual branchesbecome yellowed andbrown. Tiny blackpin-point dots (fruitingbodies of the fungus)appear scattered onyellowed leaf surfaces;sometimes sunkencankers develop ontwigs and branches.

Prune out damagedareas. Cleary's 3336or Domain protectivetreatments may beapplied. Identify andcorrect other stressproblems.

Cabbage Black Rot (Xanthomonas)

V-shaped brown-blacklesions appear at leafedges. Veins leadingaway from lesionsbecome brown-black. Eventually stemvascular systembecomes rotted.

Sanitation; rotationaway from crucifersfor 2 years.

Camellia Algal Leaf Spot(Cephaleuros)

Red-green-brownraised circular leafspots with wavy edges.

Sanitation. See Ala.Pest ManagementHandbook.

Armillaria Root Rot Sudden dieback; rootsshow thin whitemycelial layer andsometimes blackthread-like structures(Rhizomorphs); honey-colored mushrooms arealso a diagnostic sign.

Remove the plant withassociated roots.

Botryosphaeria Canker Sunken, cracked stemlesions.

Sanitation.

Cercospora Leaf Spot Brown circular orirregular spots ofvariable size.

Sanitation. Cleary's3336 or Domainprotective sprays.

Exobasidium Gall See Azalea.

Virus Ringspots Yellow spots and ringspots; may be areduction in plantgrowth.

Sanitation.

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Centipede Brown Patch (Rhizoctonia)

Light brown, large,circular patches occuron lawns; grass bladesshow medium brownlesions.


Take-All Patch(Gaeumannomycesgraminis pv. graminis)

Patches of turfyellowing and dying.

See ANR-823. Bayleton may help. Turf replacement maybe necessary.

Cherry Septoria Leaf Spot Medium brown,angular spots (about 1cm or ¼-½ inch long)on leaf surfaces; whensevere, defoliationresults.

Sanitation.

Chrysanthemum Rhizoctonia Root Rot Roots become brown,decayed and dried.

Sanitation. See theAlabama PestManagement Hand-book.

Cleyera Anthracnose(Colletotrichum)

Reddish, black spots,blotches. Orangepustules develop inspring and summer.

Sanitation; Cleary's3336 may help.

Corn Pythium SeedlingDisease

Lower stems turn palebrown, become water-soaked, and collapse.

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Crabapple Cedar Apple Rust(Gymnosporanium)

Light yellow spots (1cm or 0.5 inch diam.)on leaves; leaf fallwhen spots arenumerous.

See the Ala. PestManagement Hand-book.

Daylily Kabatiella Leaf Spot Numerous small (5mm or ¼ inch long)brown spots; leafyellowing aroundspotted areas. Thedisease is oftenassociated with stress.

Sanitation.

Dianthus Fusarium Crown Rot Brown, dried rottedtissues on lower stems. Top dieback.

Sanitation. Crop rota-tion.

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Dogwood Spot Anthracnose(Elsinoe)

Small (1-2 mm) red-brown spots withreddish borders occuron bracts, leaves, andyoung twigs. Spottingmay be severe and newleaves may appearreduced in size; foliagedeath may result.

Sanitation; See Ala.Pest ManagementHandbook.

Anthracnose (Discula) This disease ischaracterized by leafnecrosis, twig andbranch cankers andstem dieback which allbegin in the lowerbranches and progressto the upper canopy. The disease generallybegins as purple-rimmed brown spotson leaves. Spots soondevelop into a generalblight of infectedleaves. Leaf death isfollowed byprogressive infectionand death of associatedtwigs and thenbranches.

See ANR-551 or theAla. Pest ManagementHandbook.

Euonomyus Powdery Mildew(Microsphaera)

A white powderydusting appears onupper leaf surfaces;when disease is severesome leaf distortionoccurs.


Exacum Impatiens NecroticSpot Virus

New growth wasstunted. Brown spotsand blotches werepresent on the newlymatured foliage.

Sanitation. Controlthrips.

Fern, Boston Colletotrichum LeafSpot

Brown spots/blotcheson fronds.

Sanitation. Protectivesprays of Cleary's3336.

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Fescue Brown Patch(Rhizoctonia)

Light brown, oftenlarge, circular patchesoccur on lawns; grassblades, show mediumbrown irregularlesions.


Net Blotch (Drechslera)

Typically, short,square rectangular orelongated blotches (5-10 mm or larger) withlongitudinal orhorizontal dark linepatterns develop onleaves. Line patternsresemble a net.

See Ala. PestManagement Hand-book under Helmin-thosporium Leaf Spotand Crown rot (meltingout).

Forsythia Crown Gall Woody Galls on lowerstem/trunk near the soilline.

Sanitation; croprotation to boxwood,holly, redbud or othernonsusceptible plants. See ANR-944.

Geranium Botrytis Blight Gray blotches occur onthe foliage. Wholeleaves may becomeinvolved and die. When weather is cooland moist with a highrelative humidity, adelicate webbing ofspores and hyphae canbe seen.

See the Ala. PestManagement Hand-book. Sanitation.

Bacterial LeafSpot/Stem Rot(Xanthomonas)

Black spots on leavesand stems; totalcollapse of stem mayoccur; bacteria maydevelop in vascularsystem and becomesystemic.

Strict sanitation. Bordeaux mixtureprotective sprays.

Grape Anthracnose(Gloeosporium)

Circular-irregularbrown blotches/spots(3-5 mm diam.) withbrown-black margins. Spot centers maybecome light colored& dry. Damage may

See the Ala. PestManagement Hand-book or spray guide;Sanitation.

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be severe with fruit rotand dieback.

Black Rot(Guignardia)

Medium-dark brownirregular spots(approx. 5 mm diam.)on leaves and fruit.

See Ala. PestManagement Hand-book. Sanitation orspray guide.

Hawthorn, Indian Phytophthora Root Rot Roots become brownand decayed. Outertissues easily pull awayfrom the root centralcore. Foliage wilts anddieback occurs.


Holly, Helleri Phytophthora Root Rot Roots become brownand decayed. Outertissues easily pull awayfrom the root centralcore.


Holly Colletotrichum LeafSpot

Black circular spots(about 5mm diam.)sometimes with cream-colored sporescovering centers ofspots.

Sanitation; protectivesprays of Cleary's 3336or Domain may beused.

Phyllosticta Leaf Spot Small (1-2mm diam.)black spots sometimeswith a whitish center.

Sanitation; protectivesprays of Cleary's 3336or Domain may beused.

Hydrangea Botrytis BlossomBlight

Blossoms are brown-gray spotted/blotched.

Sanitation. See ANR-912 for fungiciderecommendations.

Hydrangea, Oak Leaf Bacterial Leaf Spot Small (2-5mm), dark,angular spots onleaves.

Sanitation; irrigate atsoil level.

Impatiens Alternaria Laf Spot Dark brown-black,angular leaf spots.

Sanitation; Kocide101.

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Plant Disease Description ControlPythium Root Rot Roots become pale

brown and decayed. Outer tissues easilypull away (separate)from the inner centralcore. Foliage isstunted, wilted.

Iris Heterosporium LeafSpot

Small-large (¼-½ inchlong), elliptical or ovalshaped medium brownleaf spots.


Borers/Soft Rot(Erwinia)

Leaves and rhizomesbecome decayed with awet, foul-smelling rot;wounds are oftenevident in the rhizomerotted areas. Woundsare often caused by theiris borer, but otherinsects may beinvolved.

Sanitation. Especiallyin the fall, all diseasedrhizomes should bedestroyed. To furtherprevent & controlborers, an insecticidedust may be appliedweekly in the springfrom new growthinitiation to thebeginning of June.

Ivy, English Botryosphaeria Canker Elongated, sunken,cracked stem lesions.

Pruning. Protectivesprays of Cleary’s3336.

Anthracnose (Colletotrichum)

Brown irregular spots(3 mm diam. & larger)that sometimes occuralong veins.

Sanitation. See theAla. Pesticide Hand-book. Use Cleary's3336 or Domain.

Bacterial Leaf Spot Small (2-4mm diam.),angular, dark leaf spotswith wet looking edgeson leaves.

Sanitation. See theAla. Pest Manage-mentHandbook.

Edema Small, brown, corkyspots on lower leafsurfaces.

Reduce irrigation.

Fusarium/PythiumRoot Decay

Roots become browndecayed, dried andalso wet rotted.

Sanitation. Banrotprotective treatments.

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Japanese Pagada Tree Nectria Canker Sunken canker withtiny orange raisedspecks scattered overlesion.

Sanitation.

Juniper Phomopsis Tip Blight Dieback. Pruning; Fungicideapplication. See theAla. PesticideHandbook.

Cedar-Apple Rust(Gymnosporangium)

Large woody sphericalgalls (2-5 cm diam.)become covered withorange, jelly-likefinger-like projections.

See ANR-468.

Cedar-Quince orHawthorn Rust(Gymnosporangium)

Orange powderysunken cankers.

See ANR-468.

Leyland Cypress Cercospora NeedleBlight

Beginning with lowerbranches and innerneedles, blightdevelops and spreadsupward & outward.

Sanitation; protectivesprays of Cleary's3336.

Seiridium Canker Elongated sunkenlesions on trunkusually with sapoozing around lesionedge.

Pruning. See Ala. PestManagementHandbook.

Ligustrum Macrophoma LeafSpot

Brown circular or ovalleaf spots.

Sanitation; Cleary's3336 or Domainprotective sprays.

Lilac Bacterial Leaf Spot Dark angular spots. Sanitation. Do notwater overhead.

Liriope Anthracnose (Colletotrichum)

Brown lesions onleaves, some on leaftips.

Sanitation. Protectivesprays with Cleary's3336.

Lupin Rhizoctonia LowerStem Decay

Dark brown, blacklower stem dry rot.

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Magnolia, Southern Algal Leaf Spot(Cephaleuros)

Green or red-brown,slightly raised, circularspots (1 cm diam.)with slightly wavymargins.

Usually none. Sanitation.

Phyllosticta Leaf Spot Brown irregular spots(3 mm diam. andlarger) which oftenbecome brownbordered with lightercenters as spots age.

Sanitation. Protectivesprays of Cleary's 3336or Domain.

Magnolia Stress Many older leavesbecome yellow andthen brown; excessiveleaf drop. (Some leafsenescence is normalduring April-June.)

Water when conditionsare droughty.

Maple, Japanese Anthracnose(Kabatiella)

Brown, irregularly-circular spots whichoften follow along leafveins. Spots beginsmall, but may developto involve largerportions of leaves.


Phomopsis Canker Brown-gray ellipticalsunken lesions onsmaller branches,twigs.

Sanitation.

Maple, Red Phyllosticta Leaf Spot Circular pale brownspots with darkerbrown borders (about¼ inch diam.).

--

Pythium Root Rot(Seedlings)

Roots brown, water-soaked, rotted.

Sanitation. Reducewatering schedules.

Marigold Alternaria Leaf Spot Black circular orirregular leaf spots (1-3 mm diam.).


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Mayhaw (Hawthorn) Cedar-Quince Rust(Gymnosporangium)

Yellow irregular spotswith tiny white-orangeaecial cups (sporemasses) developing onlower leaf surfacesopposite upper leafyellow spots.

Removal of cedarcankers. See ANR-468.

Mondograss Root Knot Nematode(Meloidogyne)

Poor growth; rootgalls.

Sanitation. See ANR-689 and ANR-856.

Monkey Grass (Liriope)

Anthracnose (Colletotrichum)

Pale brown blotchesand spots on foliage. Blotch margins aresometimes dark brownor red-brown. Spotsmay involve largesections of leaves. Often leaf tips areinvolved.

Sanitation; Protectivesprays of Cleary's 3336or Domain may beused.

Oak Anthracnose(Apiognomonia)

Brown-black spots andirregular blotcheswhich often developalong leaf edges and/orleaf veins.


Algal Leaf Spot(Cephaleuros)

Gray-green or brown-red spots with irregularmargins (1 cm or ¼inch diam.) on leaves;spots may coalesce.


Hypoxylon Canker Environmentalstressed oak maydevelop a diebackwhere Hypoxylon actsto hasten the diebackproblems. The funguscauses decay of innerbark and sapwood andsilver gray or coalblack stroma developsin the decay area,causing the bark tocrack and fall away.

Pruning and treeremoval.

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Plant Disease Description ControlOak Leaf Blister(Taphrina)

Concave-convex spots(10-15 mm or ¼-½inch diam.) on leaves. As spots age, theychange from a lightgreen-brown color to amedium-dark brown.


Powdery Mildew White powdery dust-ing on leaves; infectednew growth may bedeformed.

Sanitation of leaves inthe fall.

Oats Barley Yellow DwarfVirus

Leaves are yellowishred; stunting; ex-cessive tillering.

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Loose Smut (Ustilago) The seed heads of oatsbecome filled with theblack sooty masses offungal spores.

Seed treatment.

Pansy Cercospora Leaf Spot Black superficial,slightly raised spotswith ropey appearanceand irregular featheryspot edges.


Colletotrichum LeafSpot

Circular gray spotswith dark borders.


Thielaviopsis BlackRoot Rot

Black lesions on roots. Plants are stunted.

Sanitation. See theAla. Pest ManagementHandbook.

Peach Bacterial Canker-Gummosis(Pseudomonas)

Sunken, wet blackenedareas on trunk/branches. There isusually excessive gumproduction associatedwith the canker. Acharacteristic sour-foulsmell is often presentwhen the canker is cut.

Sanitation.

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Bacterial Leaf Spot(Xanthomonas)

Circular black spots(2-5 mm) develop onleaves. As spots age,they dry out and fallout, leaving circular'shot holes' in theleaves.

See the Peach SprayGuide, ANR-8.

Brown Rot (Monilinia) A gray-brown blossomblight with subsequenttwig blight and cankerdevelopment. Fruit rotfollows. Sporeproduction gives rottedtissues a gray powderycovering.

See Ala. Pest Manage-ment Handbook orspray guide.

Peach Leaf Curl(Taphrina)

Concave-convex spotsdevelop on leaves. Often, early 'spots' arethe color of normalleaf tissue. Severedisease causes leavesto be excessivelypuckered anddeformed and curledand somewhatthickened.

Sanitation. See theAla. Pest ManagementHandbook or sprayguide.

Phomopsis TwigCanker

Gray, sunken, ellipticalor oval cankers(lesions) (4 mm longor longer) on twigs andsmall branches.

Sanitation.

Ring Nematode(Criconemoides)

Roots poorlydeveloped; top growthis reduced.

Sanitation; croprotation or fumigation. See Ed Sikora.

Peanut Tomato Spotted WiltVirus

Poor growth; newgrowth stunted andmottled, sometimeswith ring spots or/andmosaic.

Thrips control.

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Pear Botryosphaeria Canker Sunken, elliptical oroval cracked cankerson branches andtrunks.

Sanitation.

Entomosporium LeafSpot

Red-black circularspots (5-10 mm diam.).


Fireblight (Erwinia) Black blotchesbeginning at leafedges; leaf blight;longitudinal, sunken,cracked cankers withdroplets of bacterialooze during humid,wet weather; twigblight; limb blight.


Frogeye Leaf Spot(Botryosphaeria)

Small purple flecksusually enlarge tocircular brown lesions4-5 mm in diam. Lesion margins arepurple; centers are tanor brown.


Peas, Field Pythium SeedlingDisease

Lower stems becomesoft, water-soaked andpale brown. Plants fallover.


RhizoctoniaStem/Root Rot

Lower stems developreddish-brown orbrown dried lesions. Dieback may result.

Sanitation; croprotation. See the PestManagement Hand-book.

Pepper Bacterial Leaf Spot Dark, small (2-5mm),angular leaf spots withwet looking edges.


Periwinkle Botrytis Blight Brown gray spot/blight.

Sanitation. Increaseair circulation. In-crease temperature. See the Ala. PestManagement Hand-book.

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Phyllosticta Leaf Spot Medium-brown,circular-oval spots (5mm diam.).

Sanitation; Protectivesprays of Cleary's 3336or Domain.

Phytophthora Blight Brown lesions onleaves and stems.


Thielaviopsis Root Rot Plants grow poorly. Roots have blacklesions, sections, andtips.

Sanitation. Cleary's3336 protectivedrenches.

Petunia Thielaviopsis Root Rot Plants grow poorly. Roots have blacklesions, sections, andtips.

Sanitation; Cleary's3336 protectivedrenches.

Photinia Anthracnose(Colletotrichum)

Light-brown, zonatespots (10-15 mm or _-_ inch long) sometimesassociated with leafmargins.

Sanitation; See Ala.Pest ManagementHandbook underEntomosporium LeafSpot.

Entomosporium LeafSpot

Red-black spots (5-10mm diam.) on upper &lower leaf surfaces. Spots generally havedark red-black borders. Spots may coalesce.

Pruning; Fungicidetreatment; See Cir.ANR-392.

Armillaria Trunk Rot Sudden wilt anddieback; thin whitemycelial layer beneathbark; sometimes blackthread-like rhizo-morphs and/or honey-colored mushroompresent.

Sanitation--removal ofplants.

Pine, Loblolly Fusiforme Rust(Cronartium quercuumf. sp. fusiforme)

Spindle-shaped(fusiform) swellings(galls) develop onbranches and trunks. In March-April theorange spore masses(aecia) of the fungusdevelop on the bark

Sanitation; removal ofgalled branches and/ortrees when galls occuron trunks. See the Ala.Pest ManagementHandbook.

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surface. The powderyspores cover the wholegall area. (Oaks arethe alternate host forthis fungus.)

Lophodermium(Ploioderma) NeedleCast

Last year's needlesbecome spotted,blighted, and fall off. Tiny, black football-shaped fungal fruitingbodies can be seen onneedles with hand lens.

Fungicide applied inspring and fall. SeeAla. Pest ManagementHandbook.

Rhizosphaeria NeedleBlight, Twig Blight

Needles and smalltwigs turn brown, die.

Sanitation. See sprayrecommendations forneedle cast; may needto continue in summer.

Pine, Slash Rhizosphaeria NeedleBlight

See Pine, Loblolly.

Pine, Virginia LophodermiumNeedle Cast

See Loblolly Pine.

Pine Needle Rust (Coleosporium)

Needles covered withnumerous cream-colorpustules (2-3 mm).

Remove asters andother compositeplants/weeds in thearea.

Plum Bacterial Canker(Pseudomonas)

See Peach.

Bacterial Leaf Spot(Xanthomonas)

Small (2-5 mm diam.)circular, brown-blackspots with wet-lookingmargins and dry-sometimes-shot holecenters. Older spotsoften have reddishmargins. Spots may besurrounded with ayellow zone or halo.

Sanitation.

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Black Knot(Dibotryon)

Sections of branchesbecome swollen andcovered with black,swollen, hard, fungalgrowth.

Prune; fungicidetreatment. See Cir.ANR-217 or the Ala.Pest ManagementHandbook.

Potato, Irish Bacterial Soft Rot(Erwinia spp.)

Cream-tan colored,wet rot of tubers. Asrot ages, secondarybacteria cause foulsmell.

Sanitation; avoidwounds.

Early Blight(Alternaria)

Small (1-2 mm) brownspots develop intolarger (10-15 mmlong) irregular spotswhich are brown-blackand often have a targetpattern. Spots occuron leaves and stems.


Fusarium Tuber Rot A black wet rot or adrier, brown rot oftuber; sometimescenter of rot area ishollow, sometimeswith white mycelium.

Sanitation. Avoidwounds.

Late Blight(Phytophthorainfestans)

Foliage becomesbrown spotted,blotched. Dead areasmay spread to causedeath of the wholeplant.

See Alabama PestManagement Hand-book.

Raphiolepsis Colletotrichum LeafSpot

Brown, circular-irregular shaped leafspots.

Sanitation. Protectivesprays of Cleary's3336.

Red Cedar Armillaria Root Rot Dieback and totaldeath of tree. Mushrooms or blackthread-like structuresmay develop at base oftree and just under thebark, respectively.

Sanitation.

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Rose Botrytis Blight Gray-brown irregularareas on flowers andleaves; gray myceliumand spores givespots/blotches a gray,cloudy appearance.

Lower humidity levels;increase temperatures;prune out diseasedplant parts; fungicides.

Black Spot(Diplocarpon)

Black spots (_-¼ inchdiam. or 4-8 mm) withfeathery margins.

Follow a regular sprayschedule; sanitation.

Downy Mildew(Pernospora)

Irregular pale yellowspots on upper leafsurfaces; grayish-sometimes with thread-like growth-spots onlower leaf surfaces. Leaves eventuallybecome brown,withered and drop.

Sanitation. See Ala.Pest ManagementHandbook. Decreasehumidity.

Powdery Mildew(Sphaerotheca)

Whitish powderygrowth on leafsurfaces; new growthmay be distorted;leaves dry & turnyellow then brown;leaf drop.


Ryegrass Helminthosporium(Bipolaris) Leaf Spot

Small, brown, ellipticalspots which maycoalesce.

See ANR-621 or theAlabama PestManagement Hand-book.

Shasta Daisy Alternaria Leaf Spot Gray-brown, roughlycircular spots.

Sanitation. Cleary's3336 or a benomylfungicide should givesome protectivecontrol.

Snapdragon Pythium Root Rot Foliage wilt; rootsbrown and water-soaked.


St. Augustine Brown Patch(Rhizoctonia)

See Centipede. --

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Take-All Patch(Gaeumannomyces)

Sections of turf thinout. Lesions (black)develop on stolons androots; plants yellowand die.

Soil pH and fertilizermanagement. SeeANR-823. Bayletonmay help.

Strawberry Angular Leaf Spot(Xanthomonas)

Small black, water-soaked, angular spots.

Sanitation. Kocideprotective sprays.

Anthracnose-CrownRot (Colletotrichum)

Lower stems (crowns)become brown androtted. Leaf edges turnbrown; plants witherand die.

Use healthy trans-plants.

Anthracnose Fruit Rot(Colletotrichum)

Fruit develops darkbrown, irregularsurface spots/rot areaswhich extend into theinner flesh. Whenhumidity is high,orange spore massesform on the fruit.


Botrytis Gray Mold Light-brown irregularspots, blotches onblossoms, leaves,petioles, stems, fruit. In humid weather,fungus produces a graypowdery growth overlesions.


Mycosphaerella LeafSpot (Common)

Deep purple smallspots become 3-6 mmdiam. with whitecenters and reddishedges.


Tomato Bacterial Leaf Spot(Xanthomonas)

Small black circular orangular spots thatbecome cream-coloredwith age.


Early Blight See Irish Potato.

Late Blight See Irish Potato.

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Pythium Root Rot Roots slightly off-color(brown); cortex mayeasily pull away fromroot central cylinder.

Sanitation; See theAlabama PestManagement Hand-book. Improve soildrainage.

Tomato Spotted WiltVirus

Plants stunted, wiltedwith yellow or brownspots or blotch.

Sanitation. Controlthrips.

Tulip Poplar Alternaria Leaf Spot Medium-brown,circular-irregular spots(1-2 cm or _-_ inchlong).

Sanitation.

Turnips Cercospora Leaf Spot White-light gray,circular-irregular,small-large (1 cm)spots on foliage.


Watermelon Fusarium Root Rot Lower leavesyellowed; yellowingand wilt spreadsupward in plant.

Crop rotation or plantresistant varieties.

Wheat Barley Yellow DwarfVirus

Foliage yellows,becomes stunted androot systems areabnormally shallow. Leaves may becomedistorted.

Delay planting date inthe fall; some varietiesshow moderateresistance.

Bipolaris Leaf Spot Brown irregular spots. Fungicides in somesituations; Refer to A.Hagan.

Fusarium Head Scab Seed heads bleached,shriveled and coveredwith a pink-orangemold.

Crop rotation for atleast one year.

Loose Smut (Ustilago) Spikelets become filledwith brown-blackmasses of spores.

Seed treatment;resistant varieties.

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Powdery Mildew(Erysiphe)

Leaves becomecovered with a white-buff colored powderycoating. Infectedleaves eventuallyyellow and die.


Puccinia Leaf Rust Orange-red, powdery,raised pustules (1-5mm diam.) scatteredover leaf blades.


Puccinia Stem Rust(Puccinia graminis f.sp. tritici)

Yellow flecks andorange elongatedpustules on leaves andstems; leaf blight.

Resistant varieties;fungicide protectivesprays; See Ala. PestManagement Hand-book.

Septoria Leaf Spot Yellow flecks on lowerleaves becomeirregular (1-5 - 4-15mm), lens-shaped,brown spots.

Use disease-free seed. See Ala. Pest Manage-ment Handbook orspray guide.

Septoria Leaf &Glume Blotch (S.nodorum)

Yellow, tan, or brown,oval or lens-shapedspots (about 1 cmlong) on leaves. Onglumes, a general gray-brown dis-colorationbegins at glume tip andmoves downward. Tiny black fruitingbodies may besprinkled on brownedglume areas.


Soilborne WheatMosaic Virus

Stunting; leavesdevelop yellow streaksand a 'short line' or'dash' type of mosaicpattern.

Crop rotation.

Take-All(Gaeumannomyces)

Plants are stunted andyellow with few tillers. Roots and lower stemsbecome black, rottedand brittle.

Crop rotation.

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Plant Disease Description ControlWheat Spindle StreakMosaic Virus

Elongated yellowstreaks, mosaic onleaves.

Rotate wheat out ofarea as it is soilborneby Polymyxa fungus.

Zoysia Brown Patch(Rhizoctonia)

See Bentgrass.

Exserohilum rostratumLeaf Spot and CrownRot

Small brown, ellipticalleaf spots which maycoalesce.

See ANR-621 or theAlabama PestManagement Hand-book.

Rust (Puccinia) Grass blades becomecovered with orange-brown dusty pustulesof spores.

See the Ala. PestManagement Hand-book or ANR-621.

Take-All(Gaeumannomyces)

See St. Augustine.

All Slime Mold Wet-looking thinsheets of fungusmaterial which may begreen, reddish orbrown in color. Whenthe spore stage ispresent, plant materialmay be covered with apowdery coating ofblack, brown, red oryellow spores.

Fungal sheets ormasses may bephysically removed;spore masses may bewashed off with astrong stream of water;when conditionsbecome dry, slimemolds will disappear. These fungi do notcause damage to plantsexcept for a shadingeffect.

Annual Report of the ACES Plant Diagnostic Labs

The annual reports of the Auburn and Birmingham Plant Diagnostic Labs are almost completed. As usual, we will send one copy per county, addressed to the County Agent Coordinator.

march plant diseases from the auburn - aces. · pdf fileextension plant pathology, extension...

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