RHS Level 2 Certificate Year 2 Week 20 – Fungal, bacterial and viral plant diseases and physiological disorders.
Learning Objectives <ul><li>4.  Know the problems posed by diseases in horticulture and ways in which these can be minimis...
Physiological Disorders <ul><li>Plant problems caused not by pests or disease but by some problem in the environment. </li...
Plant Disease <ul><li>Damage caused to plants by some disease causing agent – bacteria, viruses or fungi.  Collectively di...
Bacterial Disease <ul><li>Bacterial diseases colonise plant tissues, giving off toxic compounds that kill plant cells and ...
Bacterial Disease - Fireblight <ul><li>Bacteria enter through the nectaries. </li></ul><ul><li>Flowers and foliage die and...
Viral Diseases <ul><li>Viruses are the ultimate parasites – using living cells by taking over their processes to replicate...
Tobacco Mosaic Virus (TMV) <ul><li>Leaf mottling, poor growth, small fruit. </li></ul><ul><li>Spread by contact – on hands...
Carrot motley dwarf disease <ul><li>A combination of two viruses spread together. </li></ul><ul><li>Causes yellowing or re...
Fungal diseases <ul><li>Plants under stress are most susceptible to fungal infection – so growing healthy plants in the ri...
Grey Mould  Botrytis cinerea <ul><li>Wind spread spores colonise plant tissues in humid conditions producing fluffy white ...
Powdery Mildew <ul><li>White or grey dusty growth on leaves and shoots; weaken the plant </li></ul><ul><li>Controls:  cult...
Damping Off disease.   Pythium sp., Phytopthera sp and Rhizoctonia)   <ul><li>Fungal disease of seedlings; causes them to ...
Honey Fungus <ul><li>Severe fungal infection that attacks both dead and living wood. </li></ul><ul><li>Spread by tough bla...
Learning outcomes <ul><li>4 .  Know the problems posed by diseases in horticulture and ways in which these can be minimise...
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Rhs level 2 certificate year 2 week 20

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Rhs level 2 certificate year 2 week 20

  1. 1. RHS Level 2 Certificate Year 2 Week 20 – Fungal, bacterial and viral plant diseases and physiological disorders.
  2. 2. Learning Objectives <ul><li>4. Know the problems posed by diseases in horticulture and ways in which these can be minimised. </li></ul><ul><li>4.1 Define ‘plant physiological disorder’ and describe TWO such disorders </li></ul><ul><li>4.2 Define ‘plant disease’. </li></ul><ul><li>4.3 Describe the damage caused by grey mould, powdery mildew, damping off, honey fungus, rose black spot, potato blight and clubroot. </li></ul><ul><li>4.4 Describe TWO different methods of reducing the effects of EACH of the diseases stated in 4.2; methods should be selected from more than one of the control options (chemical, physical, cultural or biological) available. </li></ul><ul><li>4.5 Describe the damage caused by fire blight and describe TWO methods used to limit the spread of the disease. </li></ul><ul><li>4.6 Describe the damage caused by TWO named plant viruses. </li></ul><ul><li>4.7 Describe TWO methods by which viruses can be spread. </li></ul><ul><li>4.8 Describe TWO methods of avoiding the spread of plant viruses. </li></ul>
  3. 3. Physiological Disorders <ul><li>Plant problems caused not by pests or disease but by some problem in the environment. </li></ul><ul><li>For example: frost causes browning of foliage; strong winds, especially in winter when the ground is frozen, can cause die back in conifers. </li></ul><ul><li>Fasciation: distorted growth due to damage at the growing tips of stems, flowers and fruit. </li></ul><ul><li>Nutrient deficiencies – e.g. interveinal chlorosis in Azalea caused by iron deficiency in high pH soil. </li></ul>
  4. 4. Plant Disease <ul><li>Damage caused to plants by some disease causing agent – bacteria, viruses or fungi. Collectively disease causing agents are known as pathogens. </li></ul><ul><li>Plants do not have an immune system, unlike animals. If an individual plant survives a disease it will not be more resistant to another attack in the future. </li></ul><ul><li>Some cultivars however are genetically resistant to disease – they are less likely to get it or less affected than others in the same species. </li></ul>
  5. 5. Bacterial Disease <ul><li>Bacterial diseases colonise plant tissues, giving off toxic compounds that kill plant cells and feeding on the remains. </li></ul><ul><li>No chemical controls available – growing resistant varieties and cultural controls are the only solutions. </li></ul><ul><li>Not all bacteria are harmful – without nitrogen fixing and nitrifying bacteria the Earth would be a very different place with far fewer plants. </li></ul>
  6. 6. Bacterial Disease - Fireblight <ul><li>Bacteria enter through the nectaries. </li></ul><ul><li>Flowers and foliage die and blacken but often do not fall – scorched appearance. </li></ul><ul><li>Affects plants in the family Rosacea – Apples, Pears, Roses, Rowan, Hawthorn </li></ul><ul><li>Control – prune back to sound wood and burn infected material. </li></ul>
  7. 7. Viral Diseases <ul><li>Viruses are the ultimate parasites – using living cells by taking over their processes to replicate viral DNA. </li></ul><ul><li>Present in every part of an infected plant, even if not showing symptoms. </li></ul><ul><li>Spread by vegetative propagation from infected plants. </li></ul><ul><li>Also spread in sap by aphids and transferred between plants on tools and hands. </li></ul><ul><li>No chemical controls available. </li></ul>
  8. 8. Tobacco Mosaic Virus (TMV) <ul><li>Leaf mottling, poor growth, small fruit. </li></ul><ul><li>Spread by contact – on hands or tools. </li></ul><ul><li>Also spread in seed. </li></ul><ul><li>Controls – resistant varieties; clean hands; no smoking; clean tools; certified virus free seed. </li></ul>
  9. 9. Carrot motley dwarf disease <ul><li>A combination of two viruses spread together. </li></ul><ul><li>Causes yellowing or reddish colour on leaves and stunting. </li></ul><ul><li>Spread by willow-carrot aphid which flies in May –so early carrots and late ones least at risk </li></ul><ul><li>Control of aphid controls the virus. </li></ul>
  10. 10. Fungal diseases <ul><li>Plants under stress are most susceptible to fungal infection – so growing healthy plants in the right place is a good control. </li></ul><ul><li>Many problem fungi are normally resident in dead and decaying plant material – moving to living plant tissue through damage to stems (e.g. Clematis wilt) or via dying leaves or flower spikes. </li></ul><ul><li>Some garden fungi are beneficial – mycorrhizal fungi form beneficial symbiosis with many plant roots </li></ul>
  11. 11. Grey Mould Botrytis cinerea <ul><li>Wind spread spores colonise plant tissues in humid conditions producing fluffy white growth </li></ul><ul><li>Black fruiting bodies form which will split to release spores </li></ul><ul><li>Controls: no chemical; control humidity; cultural hygiene </li></ul>
  12. 12. Powdery Mildew <ul><li>White or grey dusty growth on leaves and shoots; weaken the plant </li></ul><ul><li>Controls: cultural hygiene to remove spores; avoid water stress; chemicals include myclobutanil (systemic) and sulphur dust (not for sulphur shy plants like gooseberries) </li></ul>
  13. 13. Damping Off disease. Pythium sp., Phytopthera sp and Rhizoctonia) <ul><li>Fungal disease of seedlings; causes them to rot at the base and die. </li></ul><ul><li>Encouraged by thick planting and cold wet soil. </li></ul><ul><li>Controls: Control humidity by not overwatering and sow thinly; use copper oxychlorate as a drench. </li></ul>
  14. 14. Honey Fungus <ul><li>Severe fungal infection that attacks both dead and living wood. </li></ul><ul><li>Spread by tough black ‘bootlaces’ through the soil and then penetrates roots and grows into the tree. </li></ul><ul><li>Visible signs are yellow or pale brown mushrooms and sudden wilting or death of plant </li></ul><ul><li>Controls – remove and burn all parts of the affected plant; use soil barriers to prevent spread </li></ul>
  15. 15. Learning outcomes <ul><li>4 . Know the problems posed by diseases in horticulture and ways in which these can be minimised. </li></ul><ul><li>4.1 Define ‘plant physiological disorder’ and describe TWO such disorders </li></ul><ul><li>4.2 Define ‘plant disease’. </li></ul><ul><li>4.3 Describe the damage caused by grey mould, powdery mildew, damping off, honey fungus, rose black spot, potato blight and clubroot. </li></ul><ul><li>4.4 Describe TWO different methods of reducing the effects of EACH of the diseases stated in 4.2; methods should be selected from more than one of the control options (chemical, physical, cultural or biological) available. </li></ul><ul><li>4.5 Describe the damage caused by fire blight and describe TWO methods used to limit the spread of the disease. </li></ul><ul><li>4.6 Describe the damage caused by TWO named plant viruses. </li></ul><ul><li>4.7 Describe TWO methods by which viruses can be spread. </li></ul><ul><li>4.8 Describe TWO methods of avoiding the spread of plant viruses. </li></ul>
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