2103 - Plant Diseases and Controls Flashcards
(36 cards)
What is a Plant Disease?
A Plant disease is a harmful disturbance of normal functions, caused by an infectious micro-organism.
- Fungi
- Bacteria
- Virus
Symbiosis
Any association between two or more organisms
Symbiotic Stratagies - Mutualism
An association, where both parties benefit.
Bee pollination of plants.
Lichen, fungi benefits from algae’s photosyntheses and fungi provide optimal conditions to grow.
Symbiotic Stratagies - Commensalism
An association where one party benefits but the other party is unaffected.
Epiphytic Orchids living on the branches of host trees.
Symbiotic Stratagies - Parasitism
An association where one organism benefits and the other is adversely affected.
All fungal diseases.
Plant disease definition cont…
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.
Fungi
- 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
Fungi - Honey Fungus (Armillaria)
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.
Fungi - Honey Fungus (Armillaria) Damage
- 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
Fungi - Honey Fungus (Armillaria) Control
- 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
Fungi - Damping Off Disease
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.
Fungi - Damping Off Disease Damage / Control
- 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
Fungi - Potato Late Blight
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.
Fungi - Potato Late Blight Damage / Control
- 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.
Fungi - Clubroot
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.
Fungi - Clubroot Damge / Control
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
Fungi - Black Spot of Roses
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.
Fungi - Black Spot of Roses Damage / Control
- 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)
Fungi - Strawberry Powdery Mildew
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.
Fungi - Strawberry Powdery Mildew Damage / Control
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
Fungi - Grey Mould (botrytis)
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.
Fungi - Grey Mould (botrytis) Damage / Control
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.
Fungi - Hollyhock Rust
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.
Fungi - Hollyhock Rust Damage / Control
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).
