R2103 4 DISEASES Flashcards
Plant disease definition
is an unhealthy condition in a plant causes by a fungus, bacteria or virus
How does the damage look: Grey mould
Fluffy light grey mass on buds, flowers, fruit and foliage
How does the damage look: strawberry powdery mildew
- Purple spots seen on the upper leaf surface
- Dry white infection gradually covers the areas of upper leaf
- Flowers might get a deep pink colouration
- Fruit may appear distorted
How does the damage look: Damping off
- Commonly the plumule of an emerging seedling is infected causing it to topple
How does the damage look: Honey fungus
Usually on trees and shrubs. In spring foliage turns yellow and wilts.
Appearance of toadstools
Plants die within weeks
How does the damage look: Rose black spot
Dark brown leaf spots
General leaf yellowing and leaf drop
How does the damage look: Potato blight
Yellowing of the foliage which quickly goes black
Blackened stems
Causes eventual death
How does the damage look: Club root
Causes damage to brassicaceae family
Infected plants show signs of wilting and yellowing of older leaves and severe stunting
The root become stubby and rotten
How does the damage look: Hollyhock rust
Orange-brown lumpy spots on stems and leaf undersides
Bright orange spots on upper leaf surface
Leaves shrivel and die
How does the damage look: Apple and pear canker
Sunken areas in both the bark on both young and old branches
How does the damage look: Fireblight
Wilting of individual branches
Quickly spreads to other branches
When slices through a stem a brown spot can be seen
How does the damage look: bacterial canker on Prunus
Swollen area on the stem with stem cracking and exudes light brown gum
How does the damage look: Potato leaf curl virus
Leaves of potato show upward curling
Leaves often light green in colour
Can cause serious reduction in potato yield
How does the damage look:Tobacco mosaic virus
Seedlings have stunted appearance
Mature plant leaves have pale green mottled appearance
Life cycle: Damping off
- Naturally occur in the soils
- Sexual spores are produced on infected root (mostly in autumn)
- The spores are then released and spread by water infecting growing roots
- Seedlings get infected and then colapse
- Survives in soil for a couple of months
Life cycle: Club root
- Survives for more than 5 years as minute spores
- They germinate on suspectable plant root
- The fungus forms jelly-life mass which causes roots to swell
- That disrupts food and nutriend flow in the plant and causes poor plant growth
- When plant matures, rotting plant roots release the spores back to the soil
Life cycle: Potato blight
- The fungus survives the winter as mycelium and sexual spores in the tubers
- Infected shoots emerge in the spring causing the spread of spores
- Spores get dispersed by water and wind infecting the plants
Life cycle: Honey fungus
- Black rhizomorphs fron infected tree travel to infect (up to 30 meters) healthy tree roots
- THe rhizomorphs get their nutrients from infected tree which helps to successfully take down newly infect tree
- Mycellum moves up the stem
- Infected plants decays and dies
- Rhizomorphs stay on the roots for 20 years or more infecting trees and shrubs nearby
Life cycle: Bacterial canker
- Bacteria exists as surface dwellers on leaves
- The bacteria is carried by rain droplets and enter young developing leaves in the summer and leaf scars and pruning wounds in autumn
- Baceria overwinters in infected plants
Life cycle: Potato leaf curl virus
- In June female peach-potato aphids feeed on infected plants and transfer it onto the new plants
- The virus multiplies in aphid
How diseases are spead: Grey mould
*Fungal spores carried by wind
How diseases are spead: Strawberry powdery mildew
Spored carried by wind, can overwinter
How diseases are spead: Damping off
By spores present in water
How diseases are spead: Honey Fungus
via underground rhizomorphs, up to 30m in the top of the soil
How diseases are spead: Rose black spot
Fungal spores, through water
How diseases are spead: Potato blight
Wind and water. Overwinters on crop debris
How diseases are spead: Clubroot
Resting spores in soil, contaminated tools and equipment
How diseases are spead: Hollyhock rust
By spores, can overwinter
How diseases are spead: Apple and pear canker
By spores through rain splashes, leaf scars an pruning wounds
How diseases are spead: Fireblight
Bees infecting the blossom, contaminated tools, wind-blown rain
How diseases are spead: Tobacco mosaic virus
Enters through micro wounds on root hairs or broken branches, spread on fingers
How diseases are spead: potato leaf curl virus
Peach potato aphids and wounds
How diseases are spead: bacterial canker on Prunus
Wind blown rain, leaf scars and wounds
Control: Grey mould
Cultural: avoid overcrowding the plants
Physical: removal and disposal of infected material
Control: Strawberry powdery mildew
Cultural: grow resistant cultivars
Chemical: Systemic fungicide
Control: Damping off
Cultural: water from below with tap water (not rain water)
Chemical: not available
Control: Honey fungus
Physical: excavate whole infected tree and roots
Cultural: Plant resistant species i.e. Ginkgo biloba
Control: Rose blackspot
Physical: Remove fallen, infected leaves and stems
Chemical: Spray tebuconazole
Control: potato blight
Physical: destroy infected material
Cultural: use resistant cultivars
Control: Clubroot
Cultural: Crop rotation, maintain alkaline soil, use resistant cultivars
No chemical control available
Control: Hollyhock rust
Physical: pick-off leaves and destroy
Chemical: Tebuconazole
Control: Apple and pear canker
Physical: prune out affected material
Cultural: Keep tools clean
Control: Fireblight
Physical: prune out diseased wood
Cultural: not planting suspectable species i.e. Crataegus monogyna
Control: Tobacco mosaic virus
Physical: remove and destroy infected plants
Cultural: resistant cultivars
Control: Potato leaf curl
Cultural: plant resistant cultivars
Chemical: insecticide to protect againt peach-potato aphid
Control: Bacterial canker on Prunus sp.
Physical: prune out diseased material
Cultural: plant resistant cultivars
How to avoid spead of viruses
- Control sap sucking vectors
- Avoid propagating from infected material
- Cleaning tools and equipment
Why knowing disease cycles helps their control
By knowing disease life cycles you can use prevention metods to avoid them.
Pruning correctly also helps avoiding introduction of diseases
