PCA PLANT PATHOGENS EXAM SCRIPT 2026
COMPLETE QUESTIONS AND ANSWERS
GRADED A+
◉ What is the economical significance of plant disease . Answer: Losses
of yields, crops, inputs, and land
◉ Pathogen . Answer: a causal agent of the disease
◉ Disease . Answer: an abnormal condition that causes issues like
declined health or death of a plant
◉ Sign . Answer: the presence of a structure of a pathogen (spore,
mycelium, or even mold growth)
◉ Symptom . Answer: a plant response to a pathogen infection (decline
of growth, vigor, or even death)
◉ What are some abiotic factors that cause plant diseases . Answer:
◉ What are some biotic factors that cause plant diseases . Answer:
,◉ Obligate parasite . Answer: Unable to grow outside of a living host
(viruses)
◉ Facultative saprophytes . Answer: prefers living organic matter as a
source of nutrition but can adapt to the use of dead organic matter under
certain conditions (phytophthora)
◉ Facultative parasites . Answer: a pathogen that prefers dead inorganic
material, but can also obtain nourishment from living organic material
(bacteria)
◉ Biotrophic . Answer: Any parasite that cannot survive in a dead host
and therefore keeps it alive
◉ Necrotrophic . Answer: parasites that kill the host cells
◉ Kotch postulates . Answer: A series or guidelines used to identify the
microorganism that causes a specific disease
◉ What are the three components of plant disease triangle . Answer: the
environment, the host, and the causal agent
, ◉ What is the role of each of the component of the disease triangle .
Answer: All three must be present in order for infection to take place,
the environment must favor the causal agent and the host must be
susceptible to the causal agent
◉ How do humans impact the disease triangle . Answer: Humans can
manipulate the environment, plant host resistant varieties, and use
preventative/suppressive/eradicative pesticides all to change a piece of
the disease triangle
◉ How does one component of the triangle impact a epidemic if it does
not come into contact with the other two . Answer: If one component of
the plant disease triangle is missing the epidemic will slow to a halt, in
order for the disease to spread it must have all three parts of the triangle
◉ How can you break the environment portion of the disease triangle .
Answer: alter planting dates, remove alternative host, alter harvest dates
◉ How can you break the host portion of the disease triangle . Answer:
alternate crop, plant host resistance species
◉ How can you break the causal agent portion of the disease triangle .
Answer: Pesticide application
COMPLETE QUESTIONS AND ANSWERS
GRADED A+
◉ What is the economical significance of plant disease . Answer: Losses
of yields, crops, inputs, and land
◉ Pathogen . Answer: a causal agent of the disease
◉ Disease . Answer: an abnormal condition that causes issues like
declined health or death of a plant
◉ Sign . Answer: the presence of a structure of a pathogen (spore,
mycelium, or even mold growth)
◉ Symptom . Answer: a plant response to a pathogen infection (decline
of growth, vigor, or even death)
◉ What are some abiotic factors that cause plant diseases . Answer:
◉ What are some biotic factors that cause plant diseases . Answer:
,◉ Obligate parasite . Answer: Unable to grow outside of a living host
(viruses)
◉ Facultative saprophytes . Answer: prefers living organic matter as a
source of nutrition but can adapt to the use of dead organic matter under
certain conditions (phytophthora)
◉ Facultative parasites . Answer: a pathogen that prefers dead inorganic
material, but can also obtain nourishment from living organic material
(bacteria)
◉ Biotrophic . Answer: Any parasite that cannot survive in a dead host
and therefore keeps it alive
◉ Necrotrophic . Answer: parasites that kill the host cells
◉ Kotch postulates . Answer: A series or guidelines used to identify the
microorganism that causes a specific disease
◉ What are the three components of plant disease triangle . Answer: the
environment, the host, and the causal agent
, ◉ What is the role of each of the component of the disease triangle .
Answer: All three must be present in order for infection to take place,
the environment must favor the causal agent and the host must be
susceptible to the causal agent
◉ How do humans impact the disease triangle . Answer: Humans can
manipulate the environment, plant host resistant varieties, and use
preventative/suppressive/eradicative pesticides all to change a piece of
the disease triangle
◉ How does one component of the triangle impact a epidemic if it does
not come into contact with the other two . Answer: If one component of
the plant disease triangle is missing the epidemic will slow to a halt, in
order for the disease to spread it must have all three parts of the triangle
◉ How can you break the environment portion of the disease triangle .
Answer: alter planting dates, remove alternative host, alter harvest dates
◉ How can you break the host portion of the disease triangle . Answer:
alternate crop, plant host resistance species
◉ How can you break the causal agent portion of the disease triangle .
Answer: Pesticide application
