2. Symptoms Flashcards
List five symptoms.
- Abnormal color
- Wilt
- Death of host tissue or organ
- Abnormal growth
- Stunting
What are the two main Abnormal color symptoms?
Chlorosis and Lesions.
What is Chlorosis due to?
The yellowing of normally green tissue is due to chlorophyll destruction or failure of chlorophyll formation.
Define Lesion.
A visible disease area.
What type of Lesions can we identify on plants with abnormal color? (6)
- Leaf spot (Mycosphaerlla-strwberry and Septoria)
- Necrotic spot/dead lesion
- Stripe
- Mosaic
- Blights
- Blotch
What is the discoloration delimited by in stripe lesions?
veins
What are stripe lesions caused by?
virus, minerals and rust
Define Blights.
A disease characterized by general and rapid killing of leaves, flowers and stems. (late blight)
Define Blotch.
A disease characterized by large, and irregular in shape, spots or blots on leaves, shoots and stems.
What is wilting caused by?
The loss of rigidity and drooping of plant partsis generally caused by water insufficiency in the plant. (Higher fungi-Ascomycota: Fusarium sp. and Bacteria: Erwinia sp.)
What are the four symptoms under Death of host tissue or organ?
- Rots (severe rot=leak: Pythium)
- Damping off (Pythium)
- Canker
- Dieback
What are rots caused by?
The softening, discoloration and often desintegration of a succulent plant tissue is caused by fungal or bacterial infection.
(soft rot of potato, fruit rots, stalk rot of corn)
Define Damping off.
Destruction of seedlings near the soil line, resulting in the seedlings falling over on the ground.
(Higher fungi-Basidiomycota: Rhizoctonia and Chromista-Oomycota: Pythium)
Define Canker.
A necrotic, often sunken lesion on a stem, branch, or twig of a plant. (Fungi and bacteria)
Define Dieback.
Progressive death of shoots, branches and roots generally starting at the tip.
What are the two symptoms under Abnormal growth?
- Scab
2. Galls
Define Scab.
A roughened, crust-like diseased area on the surface of a plant organ. (Fungi and Bacteria)
Define Galls.
A swelling or overgrowth produces on a plant as a result of infection by pathogens due to hypertrophy=cell enlargement or hyperplasia= increase in cell division.
Define stunting.
Dwarfing or reduces growth of the plant in general associated with reduction in size of the plant and yield.
Define what signs are.
The pathogen or its parts or products seen on a host plant.
List the five typical signs.
- Mycelia, spores, conidia, fruiting body- asexual or sexual, sporangiophore or sclerotia, etc.
- Downy mildew
- Powdery mildew
- Rusts
- Smuts
What is Downy mildew?
A fungal disease where mycelia, sporangiophore and sporangia of the fungus are seen as white downy or fluffy growth on the surface of the plant or plant part.
(Chromista)
What is Powdery mildew?
A fungal disease where mycelia and conidia of the fungus are seen as a whitish powdery growth on the surface.
(Higher fungi: Ascomycete in Ascomycota fungi)
What are Rusts?
A disease giving rusty appearance to a plant; produce pustules which rupture and expose:
- Uredospores in uredia
- Teliospores in telia
- Aecia
- Pycnia
What are Smuts?
A disease characterized by masses of dark, powdery spores.
Smut fungi
