AGRICULTURAL CROP DISEASE MANAGEMENT
(CATEGORY 1C) IOWA COMMERCIAL PESTICIDE
APPLICATOR MANUAL VOCABULARY EXAM
COMPREHENSIVE STUDY GUIDE WITH HIGH-YIELD
PRACTICE QUESTIONS, DETAILED ANSWER
EXPLANATIONS, KEY VOCABULARY REVIEW, CROP
DISEASE IDENTIFICATION CONCEPTS, PESTICIDE
APPLICATION PRINCIPLES, AND COMPLETE
CERTIFICATION EXAM SUCCESS TOOLKIT | UPDATED FOR
2026/2027 | LATEST EDITION
plant disease - ANSWER-any abnormal condition that damages a plant
and alters its appearance or function
How plant disease vs injury occurs? - ANSWER-Plant disease is a process
and changes happen over time vs injury occurs instantly
symptoms - ANSWER-visible effects of a plant disease on the host plant;
symptoms are not the disease itself; detectable changes in color, shape,
or functions of plant
pathogen - ANSWER-parasitic organism that causes disease
Examples of symptoms - ANSWER-leaf spots, leaf blight, yellowing of
plant tissue, stunting, wilting, death of plant tissue
,Signs of plant disease - ANSWER-Different from symptoms, signs are
the physical evidence of the disease
Examples of signs - ANSWER-fungal fruiting bodies, bacterial ooze,
nematode cysts
What are the three components of the plant disease triangle? -
ANSWER-Susceptible host plant, pathogen, and favorable environment
Why is favorable environment needed in for plant diseases? -
ANSWERSusceptible plants can be exposed to large amounts of a
pathogen but will not develop the disease if the environment isn't right
for that pathogen.
Two most important environmental factors that affect disease
development? - ANSWER-temperature and moisture
What other environmental factors may affect disease development? -
ANSWER-Relative humidity, soil pH, soil texture, light, and nutrient
status
What human affected factors can also have significant effects on
disease development? - ANSWER-compaction, tillage practices, planting
depth, seed bed prep, and residue management
,How does the "disease triangle" work? - ANSWER-All three factors are
needed for disease development so disease can be prevented by
altering any one of the three factors (or sides of the triangle)
Give an example of altering the host plant factor of the disease triangle.
- ANSWER-Choosing disease resistant varieties.
Give an example of altering the pathogen factor of the disease triangle.
- ANSWER-Removing debris and weeds, rotating crops, controlling
insects that carry pathogens, using fungicides to kill pathogen
Give an example of altering the environment factor of the disease
triangle. - ANSWER-Changing row spacing, avoiding overhead irrigation
What are the 4 major groups of plant pathogens? - ANSWER-Fungi,
bacteria, viruses, nematodes
How do most fungi reproduce? - ANSWER-Through spores, spores are
carried via wind and water
What symptoms can fungi cause? - ANSWER-leaf spots, leaf blights,
root rots, seedling blights, wilts, and stalk rots
Example of fungal diseases. - ANSWER-frogeye leaf spot of soybean,
anthracnose in corn, and leaf spot diseases of alfalfa and small grains
, True or False: Bacteria produce spores or fruiting bodies. -
ANSWERFalse; bacteria do not produce spores or fruiting bodies, they
divide and create colonies
How do bacteria spread from plant to plant? - ANSWER-Wind-driven
rain and gain entrances through openings in the plant (natural and
wounds from insect feeding or damage)
What are some typical symptoms of bacterial diseases? - ANSWER-Leaf
spots, water soaking of tissue, and soft rots of tissue
Common bacterial diseases in Iowa? - ANSWER-Bacterial wilt of alfalfa,
bacterial blight of soybean, holcus leaf spot of corn, and Stewart's wilt
of corn
What makes viruses different from bacteria and fungi? -
ANSWERViruses are not complete living systems; need a wound or
natural opening to penetrate plant
How are many viruses transmitted? - ANSWER-Through vectors - insects
that can carry the virus from plant to plant; equipment or people
spreading sap or juice from diseased plants to healthy plants
(CATEGORY 1C) IOWA COMMERCIAL PESTICIDE
APPLICATOR MANUAL VOCABULARY EXAM
COMPREHENSIVE STUDY GUIDE WITH HIGH-YIELD
PRACTICE QUESTIONS, DETAILED ANSWER
EXPLANATIONS, KEY VOCABULARY REVIEW, CROP
DISEASE IDENTIFICATION CONCEPTS, PESTICIDE
APPLICATION PRINCIPLES, AND COMPLETE
CERTIFICATION EXAM SUCCESS TOOLKIT | UPDATED FOR
2026/2027 | LATEST EDITION
plant disease - ANSWER-any abnormal condition that damages a plant
and alters its appearance or function
How plant disease vs injury occurs? - ANSWER-Plant disease is a process
and changes happen over time vs injury occurs instantly
symptoms - ANSWER-visible effects of a plant disease on the host plant;
symptoms are not the disease itself; detectable changes in color, shape,
or functions of plant
pathogen - ANSWER-parasitic organism that causes disease
Examples of symptoms - ANSWER-leaf spots, leaf blight, yellowing of
plant tissue, stunting, wilting, death of plant tissue
,Signs of plant disease - ANSWER-Different from symptoms, signs are
the physical evidence of the disease
Examples of signs - ANSWER-fungal fruiting bodies, bacterial ooze,
nematode cysts
What are the three components of the plant disease triangle? -
ANSWER-Susceptible host plant, pathogen, and favorable environment
Why is favorable environment needed in for plant diseases? -
ANSWERSusceptible plants can be exposed to large amounts of a
pathogen but will not develop the disease if the environment isn't right
for that pathogen.
Two most important environmental factors that affect disease
development? - ANSWER-temperature and moisture
What other environmental factors may affect disease development? -
ANSWER-Relative humidity, soil pH, soil texture, light, and nutrient
status
What human affected factors can also have significant effects on
disease development? - ANSWER-compaction, tillage practices, planting
depth, seed bed prep, and residue management
,How does the "disease triangle" work? - ANSWER-All three factors are
needed for disease development so disease can be prevented by
altering any one of the three factors (or sides of the triangle)
Give an example of altering the host plant factor of the disease triangle.
- ANSWER-Choosing disease resistant varieties.
Give an example of altering the pathogen factor of the disease triangle.
- ANSWER-Removing debris and weeds, rotating crops, controlling
insects that carry pathogens, using fungicides to kill pathogen
Give an example of altering the environment factor of the disease
triangle. - ANSWER-Changing row spacing, avoiding overhead irrigation
What are the 4 major groups of plant pathogens? - ANSWER-Fungi,
bacteria, viruses, nematodes
How do most fungi reproduce? - ANSWER-Through spores, spores are
carried via wind and water
What symptoms can fungi cause? - ANSWER-leaf spots, leaf blights,
root rots, seedling blights, wilts, and stalk rots
Example of fungal diseases. - ANSWER-frogeye leaf spot of soybean,
anthracnose in corn, and leaf spot diseases of alfalfa and small grains
, True or False: Bacteria produce spores or fruiting bodies. -
ANSWERFalse; bacteria do not produce spores or fruiting bodies, they
divide and create colonies
How do bacteria spread from plant to plant? - ANSWER-Wind-driven
rain and gain entrances through openings in the plant (natural and
wounds from insect feeding or damage)
What are some typical symptoms of bacterial diseases? - ANSWER-Leaf
spots, water soaking of tissue, and soft rots of tissue
Common bacterial diseases in Iowa? - ANSWER-Bacterial wilt of alfalfa,
bacterial blight of soybean, holcus leaf spot of corn, and Stewart's wilt
of corn
What makes viruses different from bacteria and fungi? -
ANSWERViruses are not complete living systems; need a wound or
natural opening to penetrate plant
How are many viruses transmitted? - ANSWER-Through vectors - insects
that can carry the virus from plant to plant; equipment or people
spreading sap or juice from diseased plants to healthy plants
