PCA - Plant Pathogens [2026/2027] | UPDATED
ACTUAL Exam Question and Answer with
Rationales | A+ Verified
• Economic significance of plant diseases -✓✓ Losses of yield, crops, inputs, land
• Pathogen -✓✓ Causal agent of disease
• Signs of disease -✓✓ Structures of the pathogen
• Symptoms of disease -✓✓ Plant response to pathogen infection
• Abiotic factors of plant disease -✓✓ Air pollution, temperature, nutrients
• Biotic factors of plant disease -✓✓ Living organisms (fungi, bacteria, viruses)
• Obligate parasite -✓✓ unable to grow outside of a living host
• Facultative saprophyte -✓✓ prefers living organic matter as a source of nutrition but
can adapt to the use of dead organic matter under certain conditions
• Facultative parasite -✓✓ A pathogen that prefers dead inorganic material, but can also
obtain nourishment from living organic material
• Biotroph -✓✓ Any parasite that cannot survive in a dead host and therefore keeps it
alive
• Necrotroph -✓✓ Parasite that kills host cells
• Koch's Postulates -✓✓ series of guidelines used to identify the microorganism that
causes a specific disease
• Three components of disease triangle -✓✓ Causal agent, environment, host
• Role of each component of disease triangle -✓✓ All three must be present for disease
to occur. Environment must favor causal agent. Host must favor causal agent.
• How humans impact each component of disease triangle -✓✓ Manipulate the
environment, host-plant resistance, preventative/suppressive/erradicative pesticides
,• Impact of epidemic when one component of disease triangle does not come into
contact with the other two components -✓✓ Slows epidemic to a halt. Disease spread
needs all three components interacting
• Management strategy to break environment component -✓✓ Alter planting dates,
remove alternative hosts, alter harvest
• Management strategy to break host component -✓✓ Alternate crop, host-plant
resistance
• Management strategy to break causal agent component -✓✓ Pesticide applications
• How can knowledge of plant disease triangle be used in diagnosis? -✓✓ Can rule out
different pathogens based on host and environment.
• Epidemiology -✓✓ Branch of medical science concerned with the incidence,
distribution, and control of diseases that affect large numbers of people.
• Environmental factors that affect epidemics -✓✓ Temperature, humidity, moisture, soil
pH, nutrient availability, air movement
• Importance of time in the development of an epidemic -✓✓ Epidemics develop very
quickly if conditions are favorable. It is critical to reduce the rate of infection during
susceptible life stages of the plant
• How does type of reproduction cycle affect development of an epidemic -✓✓
Polycyclic epidemics can develop much more rapidly than monocyclic epidemics
because of secondary inoculum production.
• How does dissemination affect development of an epidemic -✓✓ Conditions that
increase dissemination will accelerate development of epidemics
• Monocyclic disease -✓✓ Disease that only has a primary infection cycle
• Polycyclic disease -✓✓ Disease that produces a secondary inoculum, and has a
secondary infection cycle in addition to a primary infection cycle
• Why are monocyclic diseases less likely to result in serious epidemics? -✓✓
Controlling primary inoculum is much easier than controlling primary and secondary
inoculum. Once primary inoculum is controlled and dissemination is controlled, the
disease essentially stops developing.
, • How do sanitation practices impact monocyclic diseases? -✓✓ Epidemic may be
delayed, but severe epidemic can still occur if environmental conditions are favorable
for disease development
• How do sanitation practices impact polycyclic diseases? -✓✓ Reducing primary
inoculum may reduce the amount of secondary inoculum produced. If rate of infection is
high, there is little effect. But if rate of infection is low, it may reduce an epidemic
• Formae specialis -✓✓ Indicates a fungus is adapted to a specific host
• Incubation period -✓✓ interval between initial infection and first signs and symptoms
• Infection -✓✓ Invasion of a plant by a pathogen
• Infestation -✓✓ Large numbers of pathogen present causing damage
• Inoculum -✓✓ Infecting agent of a pathogen
• Latent infection -✓✓ infection in which the infectious agent is present but not causing
symptoms
• Mummy -✓✓ Dead, shriveled fruit that a pathogen may overwinter in
• Overwintering -✓✓ the process by which some organisms pass through or wait out the
winter season
• Pathovar -✓✓ subdivision of a plant pathogenic bacterial species defined by host
range
• Propagule -✓✓ Portion of a plant which is used to generate a new plant
• Race -✓✓ Strain of a virus adapted to a specific host
• Soil inhabitant/soil resident -✓✓ Pathogen that can survive in the soil for long periods
of time
• Soil transient/soil invader -✓✓ Pathogen that can survive in the soil for a short period
of time
• Vector -✓✓ An organism that can transport and transmit a disease
• Apothecium -✓✓ cup-shaped ascocarp
• Ascocarp -✓✓ Fruiting body of an ascomycete
ACTUAL Exam Question and Answer with
Rationales | A+ Verified
• Economic significance of plant diseases -✓✓ Losses of yield, crops, inputs, land
• Pathogen -✓✓ Causal agent of disease
• Signs of disease -✓✓ Structures of the pathogen
• Symptoms of disease -✓✓ Plant response to pathogen infection
• Abiotic factors of plant disease -✓✓ Air pollution, temperature, nutrients
• Biotic factors of plant disease -✓✓ Living organisms (fungi, bacteria, viruses)
• Obligate parasite -✓✓ unable to grow outside of a living host
• Facultative saprophyte -✓✓ prefers living organic matter as a source of nutrition but
can adapt to the use of dead organic matter under certain conditions
• Facultative parasite -✓✓ A pathogen that prefers dead inorganic material, but can also
obtain nourishment from living organic material
• Biotroph -✓✓ Any parasite that cannot survive in a dead host and therefore keeps it
alive
• Necrotroph -✓✓ Parasite that kills host cells
• Koch's Postulates -✓✓ series of guidelines used to identify the microorganism that
causes a specific disease
• Three components of disease triangle -✓✓ Causal agent, environment, host
• Role of each component of disease triangle -✓✓ All three must be present for disease
to occur. Environment must favor causal agent. Host must favor causal agent.
• How humans impact each component of disease triangle -✓✓ Manipulate the
environment, host-plant resistance, preventative/suppressive/erradicative pesticides
,• Impact of epidemic when one component of disease triangle does not come into
contact with the other two components -✓✓ Slows epidemic to a halt. Disease spread
needs all three components interacting
• Management strategy to break environment component -✓✓ Alter planting dates,
remove alternative hosts, alter harvest
• Management strategy to break host component -✓✓ Alternate crop, host-plant
resistance
• Management strategy to break causal agent component -✓✓ Pesticide applications
• How can knowledge of plant disease triangle be used in diagnosis? -✓✓ Can rule out
different pathogens based on host and environment.
• Epidemiology -✓✓ Branch of medical science concerned with the incidence,
distribution, and control of diseases that affect large numbers of people.
• Environmental factors that affect epidemics -✓✓ Temperature, humidity, moisture, soil
pH, nutrient availability, air movement
• Importance of time in the development of an epidemic -✓✓ Epidemics develop very
quickly if conditions are favorable. It is critical to reduce the rate of infection during
susceptible life stages of the plant
• How does type of reproduction cycle affect development of an epidemic -✓✓
Polycyclic epidemics can develop much more rapidly than monocyclic epidemics
because of secondary inoculum production.
• How does dissemination affect development of an epidemic -✓✓ Conditions that
increase dissemination will accelerate development of epidemics
• Monocyclic disease -✓✓ Disease that only has a primary infection cycle
• Polycyclic disease -✓✓ Disease that produces a secondary inoculum, and has a
secondary infection cycle in addition to a primary infection cycle
• Why are monocyclic diseases less likely to result in serious epidemics? -✓✓
Controlling primary inoculum is much easier than controlling primary and secondary
inoculum. Once primary inoculum is controlled and dissemination is controlled, the
disease essentially stops developing.
, • How do sanitation practices impact monocyclic diseases? -✓✓ Epidemic may be
delayed, but severe epidemic can still occur if environmental conditions are favorable
for disease development
• How do sanitation practices impact polycyclic diseases? -✓✓ Reducing primary
inoculum may reduce the amount of secondary inoculum produced. If rate of infection is
high, there is little effect. But if rate of infection is low, it may reduce an epidemic
• Formae specialis -✓✓ Indicates a fungus is adapted to a specific host
• Incubation period -✓✓ interval between initial infection and first signs and symptoms
• Infection -✓✓ Invasion of a plant by a pathogen
• Infestation -✓✓ Large numbers of pathogen present causing damage
• Inoculum -✓✓ Infecting agent of a pathogen
• Latent infection -✓✓ infection in which the infectious agent is present but not causing
symptoms
• Mummy -✓✓ Dead, shriveled fruit that a pathogen may overwinter in
• Overwintering -✓✓ the process by which some organisms pass through or wait out the
winter season
• Pathovar -✓✓ subdivision of a plant pathogenic bacterial species defined by host
range
• Propagule -✓✓ Portion of a plant which is used to generate a new plant
• Race -✓✓ Strain of a virus adapted to a specific host
• Soil inhabitant/soil resident -✓✓ Pathogen that can survive in the soil for long periods
of time
• Soil transient/soil invader -✓✓ Pathogen that can survive in the soil for a short period
of time
• Vector -✓✓ An organism that can transport and transmit a disease
• Apothecium -✓✓ cup-shaped ascocarp
• Ascocarp -✓✓ Fruiting body of an ascomycete
