W3, Biology and diagnosis of plant pathogens Flashcards
(71 cards)
What’s the plant?
What’s the disease?
Soft rot in apple
What’s the plant?
What’s the disease?
Black spot on field pea
What’s the plant?
What’s the disease?
Grapevine leaf roll
What’s the plant?
What’s the disease?
Downy mildew on grapevine
What’s the plant?
What’s the disease?
Powdery mildew on cucumber
What’s the disease?
Mosaic virus
What’s the disease?
Damping off (post emergence)
What’s the plant?
What’s the disease?
Powdery mildew on grapevine
What’s the plant?
What’s the disease?
How can you tell it apart from other diseases that it resembles?
Shot hole in almond
→ Red discolouration that looks like rust pustules, but don’t rub off.
→ Holes eventually form in the leaf once the discoloured areas fall out
What’s the disease (of the plant on the right)?
Phytophthera root rot
What’s the genus?
What’s the disease?
Rust on Prunus
What type of plant is this and what disease does it have?
Shot hole disease in stone fruit
What’s the plant?
What’s the disease?
What other symptoms occur that aren’t visible in the image?
How can you tell it apart from other diseases that it resembles?
Almond rust (aka prune rust)
→ Red/orange dots on the underside of the leaf
→ If the pustules rub off, its rust. If they don’t it’s probably the early stages of shot hole disease.
What’s the disease?
Damping off (pre-emergence)
What’s the plant?
What’s the disease?
Witches broom of willow
What’s the disease?
What’s the plant?
Antracnose (black spot) on grapevine
What’s the plant?
What’s the disease?
Phytophthera root rot of banksia
What’s the plant?
What’s the disease?
Sugarcane smut
What’s the plant?
What’s the disease?
Shot hole in almond
What is an easy method for distinguishing rust from other similar-looking diseases?
Rub the pustules on the under-side of the leaf - if they come off it’s rust.
What’s the plant?
What’s the disease?
How can you tell it apart from other diseases that it resembles?
Almond rust (aka prune rust)
→ If the pustules rub off, its rust. If they don’t it’s probably the early stages of shot hole disease.
What’s the difference between signs and symptoms?
Sign: Visible pathogen structures
Symptoms: Plant response to the pathogen
What’s the plant?
What’s the disease?
Botrytis bunch rot (on grapes)
What are the steps for identifying a plant pathogen?
- Identify the host species
- Perform preliminary examination of the host and/or specimen
- Prepare a list of possible causes
- Collect background information (soil condition, management history, local pest/disease outbreaks, etc.)
- Perform thorough visual examination of the specimen and record observation
- Perform low-power examination (hand lens or dissecting microscope), looking at/for:
- Fungal
- hyphae
- reproductive structures (conidia/ophores, sporangia/ophores)
- growth habit
- Nematodes
- Colour
- Size
- Any other diagnostic features
- Perform high power examination (compound microscope); look for the same things previously stated.
- Perform advanced tests
- Fungi:
- moist incubation to encourage sporulation
- culture (view under low- and high-powered microscopes)
- septa
- reproductive structures (conidia/ophores, sporangia/ophores)
- size, shape, and colour of spores
- the presence of rhizoids
- perform metabolic analysis
- Bacteria
- Culture (view under compound microscope)
- Morphology (shape, size, elevation, etc)
- Biochemistry
- Gram stain
- Infect a healthy host to confirm symptoms are a result of the pathogen
- Depends on the value of the crop/pathogen.
If no pathogen was found, the problem is environmental/nutritional/etc
When a pathogen is identified, research and prepare recommendations for management
At each stage of the process, attempt to identify the pathogen by comparing the diagnostic features observed with diagnostic information in relevant reference material.
