3.Pathogens Flashcards
1
Q
What is meant by plant disease?
A
An unhealthy condition or damage caused to a plant by bacteria, fungi or virus (collectively known as pathogens)
2
Q
Damage caused by Grey mould (Botrytis) and method of spread
Fungi
A
- Very common fungus, affects almost all living or dead plant matter
- Grey/white fuzzy mould on infected parts of plant
- Discoloration and wilting, infected areas shrivel and rot
- Enter plant through wounds (bud scars/pruning wound)
- Spores spread through wind, but also through soil and on plant remains
- It needs humidity to become active
3
Q
Control of Grey mould (Botrytis)
Fungi
A
- Strict hygiene, use clean equipment
- Cut back infected material and properly dispose
- Reduce humidity; adequate spacing between plants
- Increasing ventilation; prune to allow air flow
- No chemical controls are completely effective
4
Q
Damage caused by Damping off and method of spread
Fungi
A
- Seedlings are usually affected at soil surface
- Emerging seedlings collapse in a mass of white fungal growth
- Most occur naturally in soil and spores spread by water
5
Q
Control of Damping off
Fungi
A
- Use commercial, sterile growing media
- Brand new/ clean pots and containers
- Sowing thinly
- Do not overwater
- Good ventilation
- Crop rotation
- No chemical control
6
Q
Damage caused by Honey Fungus and methods of spread
Fungi
A
- Attack and kill roots of woody and perennial plants
- White fungal growth between bark and wood
- Upper plants of plants die - indicating failure of root system
- Cracking and bleeding of bark at base of stem
- Spreads underground by rhizomorphs through infected roots in the soil
- Can attack plants up to 30m away from source of infection
7
Q
Control of Honey Fungus
Fungi
A
- Excavation and destroy, burn all infected material
- Digging a trench and placing an impermeable barrier such as butyl rubber sheets will block rhizomorphs from spreading
- Select resistant plants, eg. Quercus, Buxus
- No chemical controls available
8
Q
Damage caused by Potato blight and method of spread
Fungi
A
- Causes rotting of tubers and fruit on potato/tomato plants
- Wilting, yellowing of foliage then turn black with Wichita bloom on underside of leaves
- Stems may blacken and whole plant die
- Tubers have dark surface spots
- Spores spread through wind/ water and land on leaves or stems
- Infected spores need water to be able to penetrate leaves
- Overwinters in rotten potatoes
9
Q
Control of Potato blight
Fungi
A
- Using resistant variety – Sarpo range (potato) Legend range (tomato)
- Rotation of crops - min 4yr
- Grow tomatoes in glass house to prevent spores from reaching fruit
- Don’t leave any potatoes in the soil
- Check warnings - smith
- Burn all diseased material, never compost
- No chemical control
10
Q
Damage caused by Clubroot and method of spread.
Fungi
A
- Causes damage to Brassicase - cabbage, cauliflower, brussel sprouts
- Chlorosis - pale/pinkish leaves
- Wilt rapidly
- Plants fail completely/reduced crop
- Stunted growth
11
Q
Control of Clubroot
Fungi
A
- Lifting and burning diseased plants
- Improve soil drainage
- Select resistant cultivars
- Raising soil pH by liming
- Crop rotation
- No Chemical control available
12
Q
Outline the lifecycle of Clubroot
Fungi
A
- Resting spores in the ground for up to 20 years.
- They germinate and infect root hairs causing distortion
- Produces jelly like mass within plant root
- Uptake of food and water is effected
- When roots degrade more spores are released into soil
13
Q
Control of Apple and pear canker
Fungi
A
- Cutting canker out or removing branch (treat exposed wood to prevent further infection)
- Avoid pruning during damp weather
- Improving drainage
- Raising pH by liming
- No chemical control available
14
Q
Damage caused by Apple and pear canker and method of spread
Fungi
A
- Round areas of dead sunken bark usually at a bud or wound
- Cambium layer killed
- Branch may become swollen, foliage and growth above dies
- Developing fruit sometimes attacked which rot and fall
- Fungus spores spread through rain splash and enter through damaged parts of plant
15
Q
Damage caused by Strawberry powdery mildew and method of spread
Fungi
A
- Purple, yellow, red spots on leaves
- Fluffy white deposit over leaf surfaces – upper first, then lower
- Leaves become stunted and shrivelled, curl upwards
- Affected fruit stunted/ distorted and dull in colour
- Airborne spores infect strawberries and Hops
- Once temperatures rise, spores are released
16
Q
Control of Strawberry powdery mildew
Fungi
A
- Mulching and watering (from below, avoid water on leaves)
- Prompt removal of infected shoots – don’t shake about
- Water soil through at the base - shouldn’t let soil dry out
- Resistant varieties - Pegasus
- Potassium bicarbonate provides resistance
17
Q
What is a bacterial disease?
A
- Bacteria are minute organisms, they can beneficial or detrimental
- More common in hotter/tropical climates
- They can cause serious problems to plant health
18
Q
Symptoms and spread of Bacterial canker of Prunus?
Bacterial
A
- Affects ‘Prunus’ genus - e.g Plum, peach, cherry, apricot
- Swollen areas on stems/cracking can occur
- Amber like resin
- Small, yellow leaves with brown spots
- Wind blown rain droplets enters through wounds/scars
19
Q
Control of Bacterial canker of Prunus?
Bacterial
A
- Use resistant root stocks/cultivars (e.g Warwickshire drooper)
- Prune affected areas in summer months
- Burn or properly dispose of infected material
- No chemical control is available
20
Q
Symptoms and spread of Fireblight?
Bacterial
A
- Causes damage to the ‘Roseatie’ family
- Flowers wither/die back followed by surrounding leaves and stems
- If bacteria reaches the trunk it may cause death within 6weeks - trunk looks like a burnt tree
- Bacterial slime can be seen in hot weather
- Can be spread by bee’s as they pollinate
- Can be spread by harmful insects such as Aphids
- Can be spread by rain
21
Q
Control of Fireblight?
Bacterial
A
- Carefully prune to 60cm below infected/stained wood
- Burn all infected material
- Sterilise all equipment
22
Q
What is a viral disease?
A
- Viruses are much smaller than bacteria, the particles take over the cell nucleus to produce more virus particles
- They are very hard to control with chemicals as the virus can penetrate the plant so deeply than any chemical would need to do the same
23
Q
Symptoms and spread of Leaf curl potato virus?
Viral
A
- Leaves become thickened/roll due to a build up of starch
- Serious reduction in yield
- Leaves can turn red/purple
- Carried by Peach potato aphid which can be blown a considerable distance by the wind
24
Q
Control of Leaf curl potato virus?
Viral
A
- Do not use last years crop as seed potato (especially if infected)
- Use cultivars such as ‘Valor’
- Remove any plants showing symptoms
- Use insecticides as a preventative measure
25
Q
Symptoms and spread of Tobacco mosaic virus?
Viral
A
- Distorted small leaves
- Yellow mottling/ mosaic pattern on leaf
- Brown streaky stem can sometimes be seen in summer
- Fruit yield can be affected e.g ripe fruit is hard an inedible
- Enters plant through micro wounds
- Can be easily spread by gardeners hands
- Virus can be passed on through seed
26
Q
Control of Tobacco mosaic virus?
Viral
A
- Heat treatment of dry seed to kill of virus
- Use Nutrient film technique to prevent use of infected soil
- Use resistant cultivars e.g Cherry wonder
27
Q
What is meant by Fungicide?
Considerations?
A
Used to prevent/cure diseases caused by fungi
Different modes of action:
- Preventative/protective - coats foliage and prevents disease from entering (must be thoroughly covered)
- Systemic - chemical is absorbed and works on the disease within the plant
Considerations
- Lower levels of toxicity however care must be taken when mixing
- Ensure plants have optimal growing conditions, good soil fertility and the right micro climate to reduce the chance of fungal infections
- Avoid introduction of affected plants
- Ensure fungicide is compatible with biological control methods and does not harm beneficial insects before use
