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    Rhs year 2 week 18 presentation Rhs year 2 week 18 presentation Presentation Transcript

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