Alternaria (Deuteromycete)

Symptoms: spots and occasionally blights, zonate lesions

Signs: generally not seen for most leaf spotting organisms

Life Cycles:

1. Various species
2. Anamorphic (Asexual)
3. Distinctive, dark-colored multicellular spores
4. can be controlled in greenhouses with UV-absorbing film (inhibits sporulation)

Symptoms: spots and occasionally blights with dark borders

Signs: generally not seen for most leaf spotting organisms

Life Cycles:

• Anamorphic
• Bipolaris (formerly Helminthosporium) maidis =(Deuteromycete Name)
• Cochliobolus heterostrophus = (Ascomycete Name)
• Sexual stage a perithecium with filamentous ascospores
• Genetic recombination led to 1970's blight epidemic

Symptoms: Diffuse blighting

Signs: hyphae and small sclertia can be seen for Botrytis under high humidity

Life Cycles:

• Anamorphic
• Gray mold most common disease of greenhouse crops and elsewhere
• Favors cool, humid, conditions
• Fungus often gains ingress through injury through decaying flower petals or damaged leaves and then advances towards healthy tissue
• Produces gray mycelium, conidia, and flat sclerotia

Symptoms: Spots and occasionally blights

Signs: generally not readily seen for most leaf spotting organisms

Life Cycles:

• Anamorphic
• many species, many hosts both dicots and monocots
• often lesion have black borders, tan centers

Symptoms: Spots and occasionally blights (shothole appearance)

Signs: generally not readily seen for most leaf spotting organisms

Life Cycles:

• Black rot is Florida's most serious grape disease
• Sexual Stage (Guignardia bidwellia) perithecia air-borne ascospores
• Asexual Stage (Phyllosticta sp.) pycnidia produces viscous conidia designed for spread by splashing water like anthracnoses

Symptoms: Conspicuous, dry lesions

Signs: Acervuli with spores

Life Cycles:

• Primary Cycle (one): Perithecia with asci (2-celled ascospores/disease forecasting)
• Secondary Cycles (many): Acervuli with conidia
• Transition: parasite become saphrophyte
• Control: Genetic resistance or use of fungicides (time of fungicide application (disease forecasting/primary cycle)(spray immediately following rain)

Symptoms: Moist soft rots, decay

Signs: Sporodochia with conidia, apothecia, mummies
Life Cycles:

• Primary cycle (one): Apothecia with asci (Ascospores discharged from mummies in Spring)
• Secondary Cycles (many): sporodochia with conidia (especially fruits)
• Transition: fruits mummify into a sclerotium-like structure
• Control: Disking up mummies will eliminate as many mummies as possible (disrupt apothecia formation in spring) (Careful handling of fruit)

Symptoms: Open, basil-like spores

Signs: Acervuli with spores

Spore Forms:

1. Anamorphs (most common)
2. Teleomorphs (less common)

Life Cycle:

• Primary life cycle (usually conidia, plant debris)
• Overlapping crops (e.g. papaya)
• Vegetative (e.g. strawberry transplants)
• Seed (e.g. bean anthracnose)

Control:

• clean cultivation, crop rotation, timely sprays, certification programs, seed certification

Erwinia tracheiphila (cucumber wilt)

Vs.

Ralstonia solanacearum (Southern bacterial wilt)

Erwinia

• Vascular wilt caused by bacteria
• very narrow host range (certain cucurbits)
• Transmitted by flea beetles (disease forecasting)

Ralstonia

Vascular wilt caused by bacteria (viscous ooze in vascular system)= symptom
Some races infect solanaceous plants, other bananas (moko)
Mostly tropical, subtropical disease
Survives in plant debris, wild hosts

1. Fusarium oxysporum
2. Verticillium
3. Erwinia tracheiphila (cucumber wilt)
4. Ralstonia solanacearum (Southern Wilt)
5. Ophiostoma ulmi (Dutch elm disease)
6. Cryphonectria parasitica (Chestnut blight)

1. Sudden wilt and death of plants
2. Premature yellowing of lower leaves
3. Vascular discoloration (for fungal wilts)
4. Viscous ooze in vascular system (for bacterial wilts)

1. Most cause sudden wilt by plugging the xylem
2. Most are soil-borne
3. Some need vectors
4. Most have restricted host ranges

• Similar to Verticillium
• Trinomials
• F. oxysporum f. sp. lycopersici (tomatoes)
• F. oxysporum f. sp. cubense (banana)
• Others infect coca, cannabis
• Subspecies have races
• Macroconidia, Microconidia, Chlamydospores
• Teleomorphs are Ascomycota

• ascomycota
• perithecia
• conidia
• introduced in the USA
• exterminated respective native hosts
• is a true vascular wilt disease
• Quarantines for this disease failed because the entire life cycle is not understood.
• Fungus thrives beneath bark

• Fungus mostly a saprophyte
• colonizes bark beetle galleries
• bark beetles emerge, feed on spring xylem
• Lesser European elm bark beetle efficient vectore
• Native American elm bark beelte inefficient vector because it feeds too early in the season

Example: Dutch elm disease

• Destroy infected trees
• remove bark from dead trees
• genetic resistance (oriental elms)

Example: Cucumber wilt

• Disease forecasting
• (spray for beetles when winters are mild)

Southern bacterial wilt

• used clean tools
• crop rotation
• fallow
• use clean planting stock

Fusarium oxysporum

vs.

Verticillium

1. both attack the xylem
2. Verticillium thrives under cool temps and high pH
3. Fusarium oxysporum thrives under warm temps

Ophiostoma ulmi (Dutch elm disease)

vs.

Cryphonectria parasitica (Chestnut blight)

1. Both introduced in the USA
2. Both exterminated respective native hosts
3. chestnut blight is a canker disease while dutch elm disease is a true vascular wilt
4. Both have perithecia and conidia

Symptoms of:

Phytophthora infestans (late blight of potato) (Oomycete)

Symptoms:

• seedling blight, damping-off fungi
• Root necrosis (root rots)
• stem cankers, stem girdling
• foliar necrosis (blights)
• tuber rot (potato late blight)

Symptoms and Signs of:

Plasmodiophora brassicae (Myxomycete, a protozoan plant pathogen)

Symptoms:

• causes clubroot; the causal agent is an obligate parasite
• conspicuous root gall, no necrosis

Signs: not evident

Symptoms and Signs of:

Sclerotium rolfsii (Deuteromycete)

Symptoms:

• root necrosis (root rots)
• stem cankers, stem girdling
• Foliar necrosis (blights)
• Tuber rot (potato late blight)

Signs:

• white mycelium spherical sclerotia

Symptoms and Signs of:

Fusarium solani (Deuteromycete)

Symptom:

• root necrosis (root rots)
• stem cankers, stem girdling
• Foliar necrosis (blights)
• Tuber rot (potato late blight)

Signs: signs not evident

Common Features and Symptoms:

Seedling Diseases

Symptoms:

• Pre-emergence damping off
• Post-emergence damping off
• Root rot
• Above ground necrosis

Common Features:

• Soils associated
• Wide host ranges

Symptoms:

Rhizoctonia solani (Basidiomycete) wide host range

Symptoms:

• below ground (root rot, stem, cankers)
• above ground (stem cankers, foliar blights)

Symptoms:

Pythium spp. (Oomycete)(Chromistic Algae) wide host range

Symptoms:

• below ground (root rot, stem, cankers)
• above ground (stem cankers, foliar blights)

• Genetic resistance
• Biological control (antagonists)
• Chemical Control= sterilized soil (autoclaving, methyl bromide), seed treatments (mercury), sprays (copper sulfate, metalaxyl for oomycetes) Others for Rhizoctonia (Thiram, captan, PNCB)
• Cultural Control= Hasten maturity (reduce nitrogen), avoid overcrowding, crop rotation, avoid contamination (pots, tools, irrigation)

Symptoms:

Citrus greening (Huanglongbing) or HLB

Symptoms:

• Yellow shoots

• Twig die-back
• Reduced fruit size and quality
• Lopsided fruit
• Bitter, inedible fruit
• Leaf mottling or discoloration 

12,000 species of unsegmented, bilaterally symmetrical wormlike organisms abundant in marine and freshwater habitats, in soil, and as parasites of plants and animals

• the order of nematodes which have odontostylets (many parasites) for mouthparts

• the order of nematodes that have stomatostylets (many parasites) for mouthparts

• the order of nematodes that have a mouth with buccal cavity (saprophytes)

1. Stomatostylets- are hollow spears associated with tylenchoids (Order Tylenchida)
2. Odontostylets- are solid, tooth-like structure associated with dorylaims (Order Dorylaimida)

1. Dwarfing, usually other symptoms of malaise, such as yellowing
2. Some cause root symptoms (galls, stubby roots)

1. Can cause wounds that increase incidences of fungal pathogens, such as Fusarium oxysporum

1. Can transmit certain viruses. Dorylaims in the genus Trichodorus transmit the tobravirus, tobacco rattle, which commonly infects potatoes, causing "corky ringspot" in Hasting, Florida.

• life cycle is complete within 3-4 weeks. Eggs hatch into larvae. There are four larval molts, after which the adults appear.

The state organization responsible for publishing the "Index of Plant Diseases of Florida"

Florida Department of Agriculture & Consumer Services

Control Methods:

Citrus greening (Huanglongbing) or HLB

• Reducing psyllid population with natural enemies (parasitic wasp= Tamarixia radiata) can limit loss due to HLB
• Pesticides will kill psyllids, but numbers of applications and quantities necessary to control populations are logistically, economically, and environmentally challenging.

General Information:

Citrus greening (Huanglongbing) or HLB

Signs of:

Phytophthora infestans (late blight of potato) (Oomycete)

Signs:

• pale, moist mycelium

Life Cyles and Structures of:

Phytophthora infestans (late blight of potato) (Oomycete)

Life Cycles and Structures:

• Facultative parasite
• Moderate host ranges
• prefers cool, wet conditions
• sporangia (inoculum dispersal)
• Will germinate directly or produce zoospores
• Oospores (dormancy), Antheridia, Oogonia

Life Cycles and Structures of:

Plasmodiophora brassicae (Myxomycete, a protozoan plant pathogen)

Life cycles and Structures:

• very restricted host range (and a disease of northern climates
• produces an intracellular plasmodium
• Plasmodium breaks up into zoospores
• require acidic soils; can be controlled by raising pH to about 7.2 or higher

Life Cycles and Structures of:

Sclerotium rolfsii (Deuteromycete)

Life cycles and Structures:

• like Rhizoctonia
• very wide host range
• mycelium white (no 90 degree branching)
• truly a hot-weather pathogen
• asexual stage without spores
• sexual stage (Basidomycota) with no conidia

Life Cycles and Structures of:

Fusarium solani (Deuteromycete)

Life Cycles and Structures:

• Moderately wide host range
• asexual stages (macro-, microconidia, chlamydospores)
• sexual stage (ascomycota)

1. Rhizoctonia solani (Basidiomycete)
2. Pythium spp. (Oomycete) Chromistic Algae
3. (Aphanomycetes)

Signs:

Rhizoctonia solani (Basidiomycete) wide host range

Signs:

• hyphae/mycelium (no spores, septate)
• no asexual spores
• sclerotia
• sexual stage not common

Signs:

Pythium spp. (Oomycete)(Chromistic Algae) wide host range

Signs:

• Hyphae/mycelium (coenocytic)
• Zoospores/sporangia
• sexual stage common
• Oospores, Oogonia, Antheridia