Plant Disease Diagnosis Quiz Key
List the four major categories of causal agents of plant disease and label as biotic or abiotic.
Answer = Plant Pathogens (biotic), Environmental factors (abiotic), Chemicals-fertilizers and pesticides (abiotic), Mechanical damage-improper cultural practices (abiotic)
What are the names of the three sides of the disease triangle and list an appropriate management practice for each label.
Answer = Susceptible Host (Plant a resistant host), Favorable environment (improve air circulation and/or drainage), Active pathogen (Remove diseased material (sanitation); use protective fungicide)
Name four ways pathogens are disseminated or spread.
Answer = water, wind, infected plant parts, insects
Fungi lack (blank) and therefore must obtain their nutrients from another source.
Answer = chlorophyll
What are the Organisms that obtain their nutrients from a living host?
Answer = parasites
True or False: Slime molds and Bird’s nest Fungi growing on mulch are saprophytes.
Answer = True
How does irrigation impact disease management in a landscape? (How can one minimize ‘disease-favorable’ conditions when irrigating?)
Answer = Overhead irrigation can spread plant diseases. Avoid watering foliage, if possible. If you need to water overhead, water early in the morning so leaves dry off more readily. Avoid excessive irrigation that might cause ‘ponding’ of water in low areas. Allow soil to dry out between watering. Continuous wet soil may cause anaerobic conditions and subsequent root death. Excessive soil moisture will also promote infection by root rot pathogens.
Name 4 categories of plant pathogens (biotic disease-causing agents).
Answer = fungi, bacteria, viruses, nematodes, phytoplasmas, parasitic plants
Match the symptom with its definition.
____ LESION A. Yellowing of normally green tissue
Answer = C
____ CANKER B. Loss of rigidity and drooping of plant parts
Answer = H
____ WILT C. A localized area of discolored, diseased tissue
Answer = B
____ NECROSIS D. Abnormal, localized swellings or tumors on roots, stems, or leaves
Answer = G
____ DIEBACK E. Sudden death of plant tissues
Answer = F
____ CHLOROSIS F. Progressive, gradual weakening and death of individual branches or shoots
Answer = A
____ GALL G. Death of tissue
Answer = D
____ BLIGHT H. A dead area on twigs, stems or branches; often discolored and sunken
Answer = E
10. What is the first major step when diagnosing a plant disease problem?
Answer = Identify the plant and know what normal plant growth should look like
11. A friend tells you that their pine is turning brown and dying. What are some of the questions you would ask your friend before suggesting what might be wrong?
Answer =
- What kind of ‘pine’ tree is it? Correct identification of conifers is necessary for accurate diagnosis of the problem. Perhaps the tree is one of the deciduous conifers (baldcypress)
- How long has it been in the site? Is this tree well established and possibly experiencing stress from a series of environmental or site-related events or is the tree recently planted (within last 3-5 years) and experiencing root stress from transplant shock (BP-31)
- What needles are turning brown – inner older needles (normal) or new growth (not normal)
- Do you see any oozing sap, insect frass, or holes in the trunk to indicate boring insects?