3.Weeds Flashcards
1
Q
What is meant by a weed?
A
- A plant of any kind growing out of place
- E.g Capsella bursa pastoris (shepherd’s purse) in the vegetable patch, this weed is a host to Club root and can spread to brassicas
2
Q
Name 4 ways weeds cause problems
A
- Reduction of plant growth and crop productivity as there is competition for water, light and nutrients
- Reduction of visual appeal of planting
- Can be hosts of pests and diseases e.g.Capsella bursa pastoris (shepherd’s purse) is a host to Club root
- They can affect drainage when growing in ditches/guttering
3
Q
What is meant by ephemeral weeds?
Give example.
A
- Has several life cycles in one growing season
- Germinate quickly throughout the year and overcrowd other developing plants
- Tend to be shallow rooted
- Important to remove plant before it seeds as large amounts are produced and are difficult to eradicate
E.g - Capsella bursa pastoris (shepherd’s purse)
4
Q
State what is meant by an annual weed
Give example.
A
- Complete their life cycle within one year
- Tend to have deeper roots than ephemeral
- Grow very quickly
- Produce large amounts of seed
E.g - Veronica persica (speedwell)
5
Q
State what is meant by perennial weed
Give example.
A
- Lives through several growing seasons or has a life cycle of more than 2 years
- Can have lateral rhizomes, deep tap or long underground roots
- Produce seeds but the underground parts are the main cause of problems
- Emerge quickly
- Any small pieces left in the ground can re-grow so irradiation is difficult and often herbicide is needed
E.g - Ranunculus repens (creeping buttercup)
6
Q
Describe the life cycle of Ranunculus repens (creeping buttercup)
A
- Common in turf, especially in heavy clay/prone to water logging
- Grows in bare patches
- Horizontal runners appear above ground in May and develop roots at their nodes
- Each new rooting point gives rise to a plantlet in the summer months
- Low growing point keeps it out of reach of mower blades
- Long fibrous roots make it drought tolerant and resistant to herbicides
- 2 years - bright yellow flowers from May - August
- Seeds may lie dormant for up to 7 years and can be dispersed by birds
Control
- Cultural = Carefully dig up the plant, ensuring growing point and roots are removed
- Cultural = Top dressing with sharp sand to improve drainage, can help to deter
- Chemical = 24d, dicamba and fluroxypyr can penetrate to roots without killing turf
- Chemical = Glyphosate in bare soil
7
Q
State 2 weeds associated with recently cultivated soil
Give example.
A
- Ephemeral, annual weeds are often brought to the surface during digging
- Perennial weeds with creeping rhizomes will quickly re-grow if pieces are left in soil
E.g - Veronica persica (speedwell)
8
Q
State 2 weeds associated with herbaceous borders
Give example.
A
- Mostly perennials, tend to grow very close to the plant so are difficult to see, creeping rhizomes can get into root systems making removal difficult
- Annual/Ephemeral weeds are very few as they are crowded out by garden plants and fairly easily removed
E.g - Taraxacum officinale (dandelion)
Aegopodium podagraria (Ground elder)
9
Q
State 2 weeds associated with woody perennial plantings
Give example.
A
- Perennial weeds can range from ground to climbing plants
E.g - Aegopodium podagraria (Ground elder)
Hedera helix (ivy)
10
Q
State 2 weeds associated with lawns
A
- Various perennial weeds grow in grass, they often form carpets and are therefore not damaged by mowers
- Broad leaves grow above the grasses eventually killing of the plants below
- Reduce visual appearance and quality of sport lawns
E.g
- Ranunculus repens (creeping buttercup)
- Bellis perennis (daisy)
11
Q
What is meant by Herbicide
Considerations?
A
- Technical name for weedkiller
Considerations
- Some weed killers will kill any plant they come into contact with (glyphosate)
- Ensure to spray at correct time/intervals
- Weeds should be growing well for herbicide to be most effective
- Be aware they can interfere with environment/ natural balances (may kill beneficial insects/plants, can be toxic to fish, 24d vapor could cause damage to nearby crops)
12
Q
What is meant by Contact herbicide?
A
- Kill or damage plants on contact with foliage, stem or root.
- Non selective
- Not translocated
- Only effective on annual weeds or perennial seedlings
- E.g Diquat = Control of annual weeds on paths and patios.
13
Q
State what is meant by Translocated herbicide
A
- Also known as systemic
- Absorbed by the plant leaves, stem/roots and translocated around all parts of plant
- Best for perennial or deep routed weeds
- Non-selective and non-residual, breaking down quickly in the soil7Eg
- Roundup - Glyphosate = Clearing Ground Elder on area of rough ground
14
Q
State what is meant by Selective herbicide
A
- Selective - Able to kill chosen weed species and leave others unaffected
- Only effective on broad-leaf (diocots)
- Mimic plant hormones to distort growth
- Leave grasses unharmed
- Applied to the foliage and are translocated
- Often slightly residual (i.e. stay in soil).
- E.g 2, 4-D = Control of broad-leaved weeds on lawns and sports greens
15
Q
State some benefits and disadvantages of using chemicals to control weeds
A
Benefits:
- Translocated chemicals can kill the whole plant which prevents regrowth from the root
- Chemicals can be residual which prevents germination of further weeds
- Chemicals are quicker to apply than manual weeding
- Chemicals can target specific weeds
Disadvantages:
- Risk of spray drift onto other plants, beneficial plants may be damaged
- Chemicals can contaminate the soil if used inappropriately
- Need appropriate equipment and storage facilities for chemicals
- There is a risk of pollution of water courses when using chemicals
