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Mikey's RHS > 2103 - Plant Diseases and Controls > Flashcards

2103 - Plant Diseases and Controls Flashcards

1
Q

What is a Plant Disease?

A

A Plant disease is a harmful disturbance of normal functions, caused by an infectious micro-organism.

  • Fungi
  • Bacteria
  • Virus
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2
Q

Symbiosis

A

Any association between two or more organisms

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3
Q

Symbiotic Stratagies - Mutualism

A

An association, where both parties benefit.

Bee pollination of plants.
Lichen, fungi benefits from algae’s photosyntheses and fungi provide optimal conditions to grow.

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4
Q

Symbiotic Stratagies - Commensalism

A

An association where one party benefits but the other party is unaffected.

Epiphytic Orchids living on the branches of host trees.

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5
Q

Symbiotic Stratagies - Parasitism

A

An association where one organism benefits and the other is adversely affected.

All fungal diseases.

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6
Q

Plant disease definition cont…

A

A plant disease is the harmful disturbance of normal function, of a plant, caused by an infectious micro-organism.

or

Any damage caused to a plant by any fungal, bacterial or viral organisms.

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7
Q

Fungi

A
  • organism with no ability to photosynthesise, so cannot manufacture their own food.
  • many live on the dead organic matter and are beneficial to the organic recycling system.
  • 10% of Fungal species are parasitic attacking living plant tissues
  • Grow as microscopic strands called Hyphae, forming large matted groups called Mycelium
  • Reproduce with spores spread by wind and rain
  • Thrive in warm and humid conditions, so therefore are most active during July/August
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8
Q

Fungi - Honey Fungus (Armillaria)

A

Spread in the soil through Rhizomorphs made of Hyphae, which can spread out rapidly, 1m per year.
From one woody plant to another. It can affect other plants up to 30m away.

Fruiting bodies (mushrooms) can be seen around the base of a plant.

Black Rhizomorphs may be found under the bark or in the soil at the base of an infected tree.
Similarly, white mycelial sheaths can be found growing several metres up the stem underneath the bark.

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9
Q

Fungi - Honey Fungus (Armillaria) Damage

A
  • Attacks woody plants
  • stunted growth, paler smaller foliage
  • premature autumn colours
  • fruit trees may produce small crops or unexpectedly large crops (final push before death)
  • little or excessive flowering
  • Cracked, weeping bark near the base of plant
  • Death
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10
Q

Fungi - Honey Fungus (Armillaria) Control

A
  • Complete removal of infected plant
  • Digging a trench around the infected plant of at least 0.45m to prevent the progress of the Rhizomorphs
  • line trench with a protective barrier
  • Rotavation of cleared root area, leaving the ground fallow for a year or more, will reduce the risk of residual rhizomorphs re-infecting woody plants.
  • no chemical control available
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11
Q

Fungi - Damping Off Disease

A

Affecting predominantly germinating seedlings in a glass house environment.
Encouraged by warm damp conditions, so can be present in the glasshouse year round.
Can affect outdoor crops in Spring.

Emerging Seedling is infected at soil level or just below. Causing it to topple. Fluffy growth may be seen at the base of the stem.
Usually occurs in blocks and areas rather than individual plants.

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12
Q

Fungi - Damping Off Disease Damage / Control

A
  • Weakened and collapsed seedlings
  • Reduction in seedling emergence

Control:

  • Strict Hygiene practise. Sterilising equipment and compost.
  • Tap water, rather than rain water.
  • Sow thinly to avoid overcrowding and lower humidity
  • Avoid overwatering
  • no suitable fungicides for home use
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13
Q

Fungi - Potato Late Blight

A

Fungal infection which affects crops in warm humid weather. Transported and spread by rainwater.
More serious in wet summers.
Watery rot of the leaves which quickly collapse.
Brown patches on leaves with a white fungi fringe on the underside of leaves.
Spored remain viable in the soil for several years.

Late season attacks may defoliate tubers, but tubers can be harvested if set, before they become infected.
Outdoor tomatoes are also at risk, though less so in a glasshouse culture.

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14
Q

Fungi - Potato Late Blight Damage / Control

A
  • Foliage turns completely brown and collapses.
  • Tubers develop reddish staining and eventually rot
Control
Cultural:
Crop rotation, 4 year gap minimum
Choose less susceptible varieties
Early crop 'Estima'
Maincrop 'Sarpo'

time control by following ‘fight against blight’ website

Chemical:
None

Physical:
Site hygiene
Dig up and burn infected material. Do not compost crops, even without a visible infection.

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15
Q

Fungi - Clubroot

A

An infection on the root of Brassicas and related plants. Leads to massive swelling and distortion of roots and stunted growth. Foliage wilts and turns purple.
Can infect the soil with moist and warm weather, mid-summer to late autumn.
Affect Cabbages, Brussel Sprouts, Cauliflowertrs, Turnips, Swededs, Radishes

Soil borne, more related to slime-mould, can live in the soil for unto 20 years.

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16
Q

Fungi - Clubroot Damge / Control

A

Swollen and distorted roots. Foliage wilts and plant is stunted. Symptoms are worse with younger plants.

Control:

  • remove weeds in the brassica family, Capsella bursa-pastoris (Shepards purse)
  • Crop Rotation, do not plant Brassicas for 4 Years
  • Continuers or raised bed with healthy soil
  • improve soil drainage
  • Lime the soil well before planting out pH 7
  • practise good site hygiene, (don’t distribute infected materials/soils)
  • buy disease free plants, certified stock
  • Resistant cultivars

no chemical controls available

17
Q

Fungi - Black Spot of Roses

A

Water borne fungal disease. Wet and Warm weather.
Dark leaf spots often followed by leaf yellowing and drop.
Can infect young shoots and have a weakening effect on the whole plant. Spots on the stems indicate stem infection too.
Overwinters on fallen leaves and reinfects plants in Spring though water splashes or from a pre-infected stem.

18
Q

Fungi - Black Spot of Roses Damage / Control

A
  • Dark leaf spots followed by yellowing.
  • Infected stems can weaken the plant

Control:

  • choose a less susceptible species or cultivar
  • remove and burn leaf litter
  • Burn infected rose printings
  • avoid overhead watering, to avoid splashing and spreading the spores.
  • contact fungicide (mancozeb)
19
Q

Fungi - Strawberry Powdery Mildew

A

Principally affects Strawberry plants, though can infect other species such as Raspberry and Blackberry.

Fungal disease infecting non-woody plants, especially the leaves, flowers and fruits.
Grey-white powdery fungus on the upper surface of leaves in spring.
Lead to red blotches and leaf curl.

Spores are produced and spread in summer, overwinters on old live leaves.

20
Q

Fungi - Strawberry Powdery Mildew Damage / Control

A

Dry white, powdery fungus appears on leaves. Can infect flowers and fruits which leaves them inedible.

Control:

  • Less susceptible cultivars ‘Elvira’
  • improve irrigation and mulch plants to conserve moisture
  • avoid overhead watering (minimise spread)
  • well ventilated / aerated conditions
  • SB Plant invigorator
21
Q

Fungi - Grey Mould (botrytis)

A

Fluffy grey mould appears on soft non-woody tissue.
Can infect most plant species including Pelargonium

Parts infected may shrivel and die, or soft brown rotting areas.

22
Q

Fungi - Grey Mould (botrytis) Damage / Control

A

Grey Mould or spots appear on non-woody plant tissues. (Stems, Leaves, Flowers, Fruits)
infected parts may shrivel and die.
Spreads through air borne spores.

Control:

  • Good tool and site hygiene
  • Avoid cool damp conditions (reduce humidity)
  • avoid overcrowding
  • increase ventilation / air flow around plants
  • reduced humidity
  • remove and destroy diseased plant material
  • no chemicals for amateur use.
23
Q

Fungi - Hollyhock Rust

A

Appear as Orange spots on the upper leaf. And globular pustules on the underneath.
Start lower down the plant and moves up.
Leaves are dropped and growth is weakened. Affects Alcea rosea and other species.

Spores spread by wind, and can overwinter.

24
Q

Fungi - Hollyhock Rust Damage / Control

A

Leaf dropping, stunted growth. Globular pustules on the underside of leaves with orange spots ontop.

Control:

  • Remove infected parts of the plant early
  • destroy badly infect plant
  • avoid overcrowding to encourage good air circulation
  • regular applications of systemic fungicide (mancozeb).
25
Q

Fungi - Apple Canker (dry canker)

A

Affects Apples and Pears and a few other species.

Cankers are areas of dead sunken bark, often tarting at a wound or a bud.
Small stems the infection may girdle the stem and kill it.
Larger branches, the cankers remain. Growing through multiple years. Older canker expose the dead wood in the centre.

Canker will eventually kill the branch above it.

Can infect developing fruit.

26
Q

Fungi - Apple Canker Damage / Control

A

Rotting fruit.
Sunken patchers of dead bark exposing dead wood
Stripped back bark, raised edges.
Branch / Stem death above the canker

Through pruning cut and damage left by falling leaves.

Control:

  • Choose less susceptible cultivars ‘Katy’
  • Avoid very susceptible cultivars
  • Improve site drainage
  • raise pH of soil
  • Cut out infected branches and Spurs. Dispose/ Burn.
  • Protective wound paint on new wounds.
  • Thin canopy to improve ventilation
  • Site/tool hygiene
  • Copper based fungicide after harvest, but before leaf drop. And again when the leaves are half fallen.
27
Q

Bacterial Disease

A

Microscopic organisms, vast majority are beneficial, with a few causing disease.
Difficult to control, as no chemical controls available. So Cultural controls are key.

28
Q

Bacterial - Fireblight

A

Bacterial disease spread by insects and rain droplets.
Affects Pears, Hawthorns and Cotoneaster spp.
Branches wilt and give a burnt appearance. Can cause serious damage to infected species.

Occurs in Humid and Warm conditions

29
Q

Bacterial - Fireblight Damage / Control

A
  • Blossoms wilt and die
  • individual branches wilt, turn burnt colour.
  • Can quickly spread and kill the plant
  • Bacterial slime can be produced in humid conditions
  • Brown stain seen when slicing through infected material

Control:

  • Grow resistant species
  • remove and burn infected plants
  • careful pruning is possible, 60cm below stained wood in early infection. Burn all waste.
  • Pruning tools must be sterilised between cuts
  • remove Crataegus hedges or buds to prevent pollinator transmission

No chemical controls

30
Q

Bacterial - Bacterial Canker of Prunus spp.

A

Not unlike fungal cankers, but wounds are wet and oozy rather than dry.
Sunken dead areas of bark developing in spring and early summer. Often accompanied by a gummy ooze.
Infection can girdle the branch, and it will rapidly die.
Small holes appear in the leaves - Shothole.

31
Q

Bacterial - Bacterial Canker Damage / Control

A

Sunken dead areas of bark developing on branches of Prunus spp. Gummy ooze develops.

Control:

  • Cut out all cankers and burn waste
  • site hygiene important as to not spread the bacteria
  • Carry out pruning in July and August when chance of infection is reduced.
  • Copper based fungicide is effective but not approved
32
Q

Viral Disease

A

Viruses invade the nucleus of plant cells, and thus ensure the disease is spread systematically throughout the plant.

Many viruses can exist in a host plant, with no symptoms, only coming apparent once transmitted to a susceptible plant.

due to the virus taking over the cell nucleus it is difficult to produce a viricide without harming the host plant.

Viruses are only spread by outside vectors, as they can not spread outside of the plant.

  • Aphids or sap-sucking insects
  • Propagation of infected plants
  • Contaminated tools

Common Viral symptoms

  • Leaf distortion
  • fruit blemeshing
  • Flower colour streaks
  • mosaic/mottling of leaves
  • stunting of plant
33
Q

Viral - Potato Leaf Curl Virus

A

Common cause of potato crop damage, can be transmitted through potato stock.

Vector is the Peach Potato Aphid.
1st season - light rolling of upper leaves, easily missed,
Overwinters in seed potatoes
2nd season - lower leaves curled with yellowing and growth stunting. Yield reduction.

34
Q

Viral - Potato Leaf Curl Virus Damage / Control

A
  • Curled, Yellowed leaves
  • Stunting
  • reduced crop / yield

Control

  • Use disease free, certified stock of seed potatoes
  • Effective aphid population control
  • Remove and burn infected material to prevent transmission
  • Site and tool hygiene
35
Q

Viral - Tobacco Mosaic Virus

A

Infects Solanaceae (tomatoes, potatoes, nightshade) and many other species. Nicotian spp.
Not often spread through Aphids, more likely through sap and vegetative prorogation, plus physical transmission by humans.
-Touch, brushing past
-unsterilised tools

Stunted growth, with light green mosaic pattern on the leaves. Brown streaks on leaves, bronze patches on fruits.

36
Q

Viral - Tobacco Mosaic Virus Damage / Control

A

May include:
Yellowing of foliage, necrotic spot leafs, mosaic mottled leaf, Stunting and leaf distortion.

Control:

  • Control transmission vectors
  • used certified seed stock
  • Less susceptible cultivars
  • Remove and burn infected plants
  • Sterilise tools, clothing, hands
  • practise good site hygiene

No chemical control.

Mikey's RHS (30 decks)

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