PLANT PATHOLOGY. Plant disease Plant’s normal function is interrupted by a pathogen or the environment

PLANT PATHOLOGYPLANT PATHOLOGY

Plant diseasePlant disease

Plant’s normal function is interrupted Plant’s normal function is interrupted by a pathogen or the environmentby a pathogen or the environment

Plant diseasePlant disease

Is this a disease?Is this a disease?

Biotic damageBiotic damage

Caused by living pathogens or Caused by living pathogens or parasitesparasites


SymptomsSymptoms: visible expressions of plant : visible expressions of plant reaction to the pathogenreaction to the pathogen


SignsSigns: indications of disease from : indications of disease from direct visibility of a pathogendirect visibility of a pathogen– Actually Actually seeing the pathogenseeing the pathogen

DISEASE TRIANGLEDISEASE TRIANGLE

Disease needs all three to developDisease needs all three to develop– Only need to block one of themOnly need to block one of them

PathogenPathogen

Organisms capable of causing diseaseOrganisms capable of causing disease FungusFungus BacteriaBacteria VirusVirus Other micro-organismsOther micro-organisms

PathogenPathogen

ParasitesParasites: obtain food from living : obtain food from living organisms (host)organisms (host)

PathogenPathogen

Obligate parasiteObligate parasite: require (obligated : require (obligated to) living plant cells as food to to) living plant cells as food to complete life cyclecomplete life cycle

PathogenPathogen

Facultative parasiteFacultative parasite: obtain nutrition : obtain nutrition from either living or dead plantsfrom either living or dead plants

PathogenPathogen

SaprophyteSaprophyte: feeds on dead organic : feeds on dead organic material on plant or in soilmaterial on plant or in soil

HOSTHOST

SusceptibleSusceptible: no ability to retard or : no ability to retard or resist diseaseresist disease

Susceptible plant tissueSusceptible plant tissue– Fertilization Fertilization

HOSTHOST

ResistanceResistance: some ability to retard or : some ability to retard or tolerate diseasetolerate disease

HOSTHOST

ImmunityImmunity: complete resistance against : complete resistance against diseasedisease

ENVIRONMENTENVIRONMENT

MoistureMoisture and and temperaturetemperature are the are the predominant factorspredominant factors


MoistureMoisture, water is , water is criticalcritical

Dry springs can reduce Dry springs can reduce disease occurrencedisease occurrence

Often 24 to 48 hours Often 24 to 48 hours continually wetness continually wetness requiredrequired

Poor irrigation practicePoor irrigation practice


TemperatureTemperature, each pathogen has , each pathogen has optimal rangeoptimal range

Predisposed condition of hostPredisposed condition of host Host is stressed, can’t defendHost is stressed, can’t defend

FUNGUSFUNGUS

The vast majority of plant diseases The vast majority of plant diseases are fungalare fungal

FUNGUSFUNGUS

What is a fungus?What is a fungus? Microscopic organisms that lack Microscopic organisms that lack

chlorophyll, cannot produce own foodchlorophyll, cannot produce own food Multicellular organism that is Multicellular organism that is

threadlike in compositionthreadlike in composition

FUNGUSFUNGUS

Enormous genetic variabilityEnormous genetic variability due to due to rapid reproductionrapid reproduction

FUNGUSFUNGUS

Species of fungi are Species of fungi are subdivided into subdivided into strainsstrains that are very specific in that are very specific in

Plant species or Plant species or cultivarscultivars

VirulenceVirulence Temperature rangeTemperature range Moisture requirementsMoisture requirements

SPORESPORE

Fungal seedFungal seed Very distinct shape and size used to Very distinct shape and size used to

differentiate pathogensdifferentiate pathogens Single celled or multi-celledSingle celled or multi-celled

SPORESPORE

AsexualAsexual, not requiring the union of , not requiring the union of sexual parts to be produced sexual parts to be produced

ConidiaConidia

SPORESPORE

SexualSexual, requiring union of sexual , requiring union of sexual parts to be producedparts to be produced– Basidiospore, ascospore, oospore…Basidiospore, ascospore, oospore…

SPORESPORE

Where do you see spores when a plant Where do you see spores when a plant is infected?is infected?

Leaf surfaceLeaf surface– Appears as mold (powdery mildew)Appears as mold (powdery mildew)

SPORESPORE

Where do you see spores when a plant Where do you see spores when a plant is infected?is infected?

Fungal fruiting bodiesFungal fruiting bodies Spore producing pocketsSpore producing pockets Sporodochium, acervulus, Sporodochium, acervulus,

pycnidium…pycnidium…

HYPHAEHYPHAE

HyphaeHyphae is what germinates out of the is what germinates out of the sporespore

Branches out into tubular filamentsBranches out into tubular filaments

HYPHAEHYPHAE

MyceliumMycelium refers to all the hyphae as refers to all the hyphae as a whole, as the fungal bodya whole, as the fungal body

Inside the plant, or outside the plant Inside the plant, or outside the plant under high moistureunder high moisture

PLANT INVASIONPLANT INVASION

Fungus enters plant through any of the Fungus enters plant through any of the followingfollowing

WoundsWounds– MechanicalMechanical, pruning or handling, pruning or handling


WoundsWounds– InsectsInsects, vectors or egg laying, vectors or egg laying


WoundsWounds– Naturally occurringNaturally occurring

Secondary roots rupture the main root when Secondary roots rupture the main root when emergingemerging

Leaf scarsLeaf scars



Natural openingsNatural openings– Lenticels Lenticels



Direct penetrationDirect penetration– Pushing through tissuePushing through tissue– Resistance can come in the form of Resistance can come in the form of

thicker cuticle or hairy leafthicker cuticle or hairy leaf

FUNGAL LIFE CYCLEFUNGAL LIFE CYCLE

Peach brown rotPeach brown rot is used as an example is used as an example


OverwinterOverwinter, ,

Disease is dormant in infected fruit Disease is dormant in infected fruit and stemsand stems


DisseminationDissemination

Disease produces spores (conidia) that Disease produces spores (conidia) that are spread by wind and rainare spread by wind and rain


InoculationInoculation

Spores contact susceptible bloomsSpores contact susceptible blooms


PenetrationPenetration

Spore germinates and enters tissue Spore germinates and enters tissue directlydirectly


InfectionInfection

Establishes hyphae in tissue and feeds Establishes hyphae in tissue and feeds on cellson cells


Incubation periodIncubation period

Time between infection and Time between infection and appearance of symptomsappearance of symptoms


InvasionInvasion

Spreads from bloom to other parts of Spreads from bloom to other parts of the plant within tissuethe plant within tissue


DisseminationDissemination……


OverwinterOverwinter

When temperature cools, fungus goes When temperature cools, fungus goes dormantdormant

Zombie FungusZombie Fungus

http://http://www.huffingtonpwww.huffingtonpost.com/ost.com/2011/09/14/2011/09/14/zombie-zombie-caterpillars-caterpillars-virus_n_962256.virus_n_962256.htmlhtml

Brazilian rain Brazilian rain forestforest

Controls antsControls ants

Infection pegs Infection pegs grow from grow from bodybody

Shoots at Shoots at passing antspassing ants

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PLANT PATHOLOGY. Plant disease Plant’s normal function is interrupted by a pathogen or the environment