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Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
Rhs year 2 week 18 presentation
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Rhs year 2 week 18 presentation

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  • 1. RHS Level 2 Certificate Year 2 Week 18 – Weeds, identification and control.
  • 2. Learning Objectives <ul><li>2. Understand the problems posed by weeds in horticulture and how these problems can be minimised. </li></ul><ul><li>2.1 Describe what is meant by a weed. </li></ul><ul><li>2.2 Describe how weeds reduce crop productivity and reduce the visual appeal of plantings for display. </li></ul><ul><li>2.3 Describe the role of weeds as alternative hosts for plant pathogens. </li></ul><ul><li>2.4 Describe the biology of ephemeral, annual and perennial weeds. </li></ul><ul><li>2.5 State the botanical names of TWO examples of EACH of the types described in 2.4. </li></ul><ul><li>2.8 State what is meant by contact, residual, translocated and selective herbicides, and describe ONE situation where EACH type would be used appropriately. </li></ul><ul><li>2.9 State the active ingredient of ONE example of EACH type of herbicide described in 2.6. </li></ul>
  • 3. What is a weed? <ul><li>Any plant in the ‘wrong’ place. </li></ul><ul><li>However some plants are generally undesirable in cultivated ground </li></ul><ul><li>Some weeds are serious invasive threats to the environment e.g. Fallopia japonica but most simply compete with cultivated plants for water, nutrients and light. </li></ul>
  • 4. Weeds as hosts for pests and diseases <ul><li>Weeds can provide pests such as aphid with a place to overwinter – leading to rapid infestation of cultivated plants in spring. </li></ul><ul><li>Weeds can also host viruses and fungal plant diseases that can then be transmitted to cultivated plants. </li></ul><ul><li>Removing weeds can break the life cycle of the pest or remove the source of disease and therefore reduce the chances of plant problems arising </li></ul>
  • 5. Types of weed <ul><li>Ephemeral – a number of generations produced from seed to seed each year. </li></ul><ul><li>Annual – germinates, grows, flowers, sets seed and dies in one year. </li></ul><ul><li>Perennial – live for a number of years, growing and flowering and setting seed each year. </li></ul>
  • 6. Ephemeral weeds <ul><li>Cardamine hirsuta – Hairy Bitter Cress; Senecio vulgaris – Groundsel. </li></ul><ul><li>Produce vast amounts of seed that remains viable in the ground for a number of years. </li></ul><ul><li>Shallow rooted and very quick growing. </li></ul>
  • 7. Annual weeds <ul><li>Chenopodium album (Fat Hen); Gallium aparine (Cleavers, Goosegrass) </li></ul><ul><li>Shallow rooted and quick growing </li></ul><ul><li>Reproduce by seed and die after setting seed. </li></ul>
  • 8. Perennial weeds <ul><li>Aegeopodium podagraria (Ground Elder); Taraxacum officinale (dandelion) and Plantago major (Greater Plantain) </li></ul><ul><li>Reproduce by seed, but also vegetatively, which makes them hard to eradicate. </li></ul><ul><li>Live and grow for many years. </li></ul><ul><li>Typically deep or extensive root systems, tap roots etc. </li></ul>
  • 9. Means of control <ul><li>Physical – hand weeding, hoeing, digging. </li></ul><ul><li>Chemical – herbicides </li></ul><ul><li>Cultural – mulching, weed fabric, ground cover plants. </li></ul>
  • 10. Herbicides <ul><li>Contact – kill what they touch e.g. diquat </li></ul><ul><li>Systemic or translocated – taken up by the plant, so they will kill all parts if enough is absorbed, e.g. glyphosate </li></ul><ul><li>Residual – usually combined with a contact herbicide, these kill emerging seedlings, e.g, metosulam. </li></ul><ul><li>‘ hormone’ or selective – kill broadleaved weeds (dicotyledons) only, e.g dicamba. </li></ul>
  • 11. Worksheet answers <ul><li>Hand weeding or hoeing – trying not to turn the soil over or damage the rows of cabbages. </li></ul><ul><li>Hand weeding – chemical control would be difficult as the hedge would also be damaged. </li></ul><ul><li>Digging or careful spot treatment with glyphosate whilst the perennials are still dormant. </li></ul><ul><li>Dicamba – selective for broadleaved weeds or a daisy grubber to dig up. </li></ul><ul><li>Very little (apart from growing a GM grass with resistance to glyphosate). </li></ul>
  • 12. Learning Outcomes <ul><li>2. Understand the problems posed by weeds in horticulture and how these problems can be minimised. </li></ul><ul><li>2.1 Describe what is meant by a weed. </li></ul><ul><li>2.2 Describe how weeds reduce crop productivity and reduce the visual appeal of plantings for display. </li></ul><ul><li>2.3 Describe the role of weeds as alternative hosts for plant pathogens. </li></ul><ul><li>2.4 Describe the biology of ephemeral, annual and perennial weeds. </li></ul><ul><li>2.5 State the botanical names of TWO examples of EACH of the types described in 2.4. </li></ul><ul><li>2.8 State what is meant by contact, residual, translocated and selective herbicides, and describe ONE situation where EACH type would be used appropriately. </li></ul><ul><li>2.9 State the active ingredient of ONE example of EACH type of herbicide described in 2.6. </li></ul>

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