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RHS L2 Sarah - 1/2/3/4 > 3.Pathogens > Flashcards

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)

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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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

RHS L2 Sarah - 1/2/3/4 (21 decks)

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