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R2103 Plant Health > Weeds > Flashcards

Weeds Flashcards

1
Q

What is meant by a weed?

A

A plant growing out of place.
A plant growing in a particular situation where it is not wanted and where potentially it will be competing with cultivated plants.
Any plant not intentionally sown or propagated by the grower that requires management to prevent it from interfering with crop or livestock production.

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2
Q

How do weeds cause problems?

A

Reduction of plant growth.
Competition for light, water and nutrients.
Reduction of the visual appeal of plantings.
Alternate hosts for plant pathogens. eg white blister rust of brassicas and club root.

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3
Q

Characteristics of weeds? (10)

A
  1. Vigorous growers.
  2. Copious seed production.
  3. Seed dispersal mechanisms so they spread away from the original plant.
  4. Rapid population establishment.
  5. Seed dormancy.
  6. Long term survival of buried seed.
  7. Germinate at low temperatures in early spring.
  8. Adapted to spread.
  9. Possess vegetative reproductive structures.
  10. Able to survive disturbance of human activities.
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4
Q

What is the most costly category of agricultural pest?

A

Weeds. Worldwide weeds cause more yield loss and add more to farmers production costs than insect pests, crop pathogens, root feeding nematodes or mammal and bird pests.

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5
Q

How do weeds outgrow cultivated plants?

A

Vigorous growth.
Ephemeral life cycle means many generations in one growing season.
Spread easily by seed or by rhizomes.
Hard to remove - persistent tap root and rhizomes which snap easily.

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6
Q

What health problems can occur to plants because of weeds?

A

May harbour pests - eg provide shelter for slugs.
May be an alternate host to disease - eg. blister rust and clubroot on brassicas.
Compete with cultivated plants for light, water and nutrients.
Physically hindering crop growth and development especially climbing vines like hedge bindweed. Calystegia sepium.
Promoting disease by restricting air circulation around the crop.

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7
Q

What is the botanical name for Shepherds purse?

A

Capsella bursa-pastoris

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8
Q

What horticultural problems do weeds cause?

A

Interfere with machinery.
Contaminate crops - eg. weed seed contaminating a seed crop.
Damage visual appearance/reduce visual appeal of planted areas.
Decreases yield through competition.

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9
Q

What is the botanical name for hairy bittercress?

A

Cardamine hirsuta

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10
Q

What is the main issue with Cardamine hirsuta? (hairy bittercress)

A

Affects surface of containers or bare soil.
Is ephemeral with short life cycle. Seedlings may appear at most times of the year, although mainly summer/autumn.
Frost hardy can survive winter.
Has explosive seed capsules - seeds can be dispersed up to 1metre away or considerably further if carried by the wind.
Ensure remove before set seed by hoeing/cultivation preferably when soils are dry.
Not usually worth using glyphosate as flowers so quickly, whereas chemicals take 2 weeks to work.

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11
Q

What is the botanical name for Shepherd’s purse?

A

Capsella bursa-pastoris

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12
Q

What are the main issues with Capsella bursa-pastoris?

A

Capsella bursa- pastoris is known by its common name Shepherd’s purse because of it’s triangular, purse like pods.
It flowers almost all year round and reproduces entirely from seed.
It persists long term in the soil - seeds can remain viable for tens of years!
Capable of producing several generations each year.
Host for club root and white blister rust and mealy cabbage aphid.
Control - hand remove, mulch, hoe, but avoid disturbing the soil too deep to bring more seeds to the surface. Stale seedbed method.
Not worth using chemicals as they flower quicker than the chemical will take to work.

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13
Q

What is the common name for Senecio vulgaris?

A

Groundsel

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14
Q

Name 3 ephemeral weeds?

A 
Senecio vulgaris (groundsel)
Capsella bursa-pastoris (shepherd's purse)
Cardamine hirsuta (Hairy bittercress)
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15
Q

Define what an annual weed is?

A

A weed which germinates, grows, flowers and sets seeds once in a single growing season.

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16
Q

What is the botanical name for Large field speedwell?

A

Veronica persica

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17
Q

Describe Veronica persica. (Large field speedwell)

A

Has weak stems that form a dense prostrate groundcover. Can crowd out young crops.
Small blue flowers.

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18
Q

How to control Veronica persica?

A

Affects veg plots and borders.
Hoe/remove by hand fork whenever seen.
Bury deeply when digging or mulching.
Chemical control with acetic acid.

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19
Q

What is the botanical name for Meadow grass?

A

Poa annua

20
Q

Where is Poa annua a problem, and how and when to treat it?

A

Affects borders, lawns, veg plots, golf courses, crevices between paving blocks.
Can flower below mow height and leads to uneven surface.
Remove whenever seen.
Control - hoeing, burying deeply when digging/mulching. Hand fork/trowel.
In lawns avoid bare patches where it will colonise.
Chemical control with contact insecticide such as acetic acid.

21
Q

Name 5 annual weeds.

A 
Veronica persica (Large field speedwell)
Poa annua (meadow grass)
Stellaria annua (chickweed)
Gallium aparine (Sticky willy)
Impatiens glandulifera (Hilmalayan balsam)
22
Q

What is a perennial weed?

A

A weed which completes it’s life cycle over several growing seasons.

23
Q

What is the botanical name for creeping buttercup?

A

Ranunculus repens

24
Q

How many methods of reproduction do perennial weeds have, and what are they?

A

Two methods of reproduction. - Vegetative and seed.
Some regrow in spring from a vegetative structure such as taproot of dandelion.
Can be woody or herbaceous.

25
Q

What areas are affected by Ranunculus repens (creeping buttercup), and how to control it?

A

Affects woodland beds, and borders and shaded areas of lawn, and bare soil. Heavy clay.
Likes poorly drained soil.
It is a weed with spreading runners and seeds.
Reproduction is usually from seeds but it also spreads via vegetative reproduction by runners.
Control by removing with hand tools, border fork and ensure growing point and main roots are remove and runners.
Autumn spiking of lawn for drainage.
Chemicals include 2, 4-D or Dicamba on lawns.
Glyphosate on bare grounds.
Carefully remove from borders using had tools or border fork.

26
Q

What is the botanical name for Ground elder?

A

Aegopodium podagraria

27
Q

Where might you see Ground elder? (Aegopodium podagraria)

A

Beds, borders, new lawns all soil types.

28
Q

How is Ground elder (Aegopodium podagraria) established and how to treat?

A

May establish from seed but usually arrives via rhizomes from neighbouring gardens, or stem fragments in composts or manures.
Leaves appear in spring/summer, but rhizomes and roots persist year round.
Control by carefully remove rhizomes with garden fork then repeat as regrows.
Or clear rhizomes, then cover with black plastic for 12 months.
Mowing ground elder in a lawn will eventually starve it.

29
Q

Give 5 examples of perennial weeds?

A
  1. Ranunculus repens (creeping buttercup)
  2. Aegopodium podagraria (ground elder)
  3. Taraxacum officinale (Dandelion)
  4. Equisetum arvense (Horsetail)
  5. Calystegia sepium (Bind weed)
30
Q

Name 3 types of chemicals (herbicides) which can be used on weeds?

A

Acetic acid
Glyphosate
2, 4 D

31
Q

How does acetic acid work?

A

Acetic acid kills only the portion of green tissue that it makes contact with.
Generally these are the fastest acting herbicide.
Less effective on perennial plants which are able to regrow from rhizomes, roots or tubers.
Non selective and non residual and work simply by scorching off weed foliage.

32
Q

What can you use acetic acid for?

A

Used on annual weeds on paths.
Small perennial seedlings such as Ranunculus repens (creeping buttercup)
Poa annua in paving.

33
Q

How does Glyphosate work?

A

Glyphosate is transported through the plant either from foliar application down to the roots, or from soil application up to the leaves.
Capable of controlling perennial plants and may be slower acting but ultimately more effective than contact herbicides.
Non selective and non residual.
Differ from contact herbicides in that when applied to the foliage the herbicide moves down into the root system.

34
Q

How is the most affective way to apply acetic acid to weeds?

A

Ensure only makes contact with weed.
Uniform spray coverage and particle size are essential for adequate control.
Ensure whole weed plant sprayed.

35
Q

When and how is the most effective time to apply Glyphosate?

A

Most effective time for spraying glyphosate is mid to late summer when the weed has a large surface area.
Ensure no contact with non weed crops/plants.
May take up to 2 weeks before yellowing an dying.
Not organic and can have detrimental effect to environment/ carcinogenic to humans.

36
Q

Which weeds can be treated with Glyphosate?

A

Deep rooted perennial weeds such as ground elder and dandelion. (Aegopodium podagraria & Taraxacum officinale)

37
Q

What are the three methods of weed control?

A

Physical - hoeing, hand weeding with fork/trowel, digging over, rotavating.
Chemical - Herbicides.
Cultural - Green manure, stale seed bed method, ground cover plants.

38
Q

State how two named annual weeds over winter?

A
  1. Capsella bursa pastoris overwinters as a seed.

2. Veronica persica overwinters as a seed.

39
Q

State how 2 named perennial weeds overwinter?

A

Taraxacum officinale overwinters as a tap root.

Aegopodium podagraria overwinters as a rhizome.

40
Q

In a recently cultivated soil, what kind of weeds might be an issue?

A

Ephemeral and annual weeds.
Seeds often already in the soil.
Germinate once exposed to light during cultivation.

41
Q

How to control ephemeral/annual weeds in a recently cultivated bed?

A

Contact herbicide as fast acting. (Acetic acid).
Hoe when young weed seedlings on a dry day.
Mulch around cultivated plants to a depth of 5 cm.
Stale seedbed method.

42
Q

Give 2 examples of weeds which could be a problem in a newly cultivated soil?

A 
Capsella bursa pastoris (shepherd's purse) - ephemeral
Cardamine hirsuta (Hairy bittercress)  - ephemeral
Stellaria media (Chickweed) - Annual
43
Q

What weeds can be an issue in a herbaceous perennial border?

A

Ephemerals and annuals, but also perennials which can prove difficult to eradicate in established plantings.
Plants may have to be dug out and weed roots teased out of root ball.
Cardamine hirsuta
Stellaria media
Taraxacum officinale

44
Q

What is the botanical name for bind weed?

A

Calystegia sepium

45
Q

What weeds can be a problem in lawns?

A

Low growing perennials which survive mowing and regenerate from vegetative structures.
Ranunculus repens. Taraxacum officinale.
Some annual weeds can infest when there are bare patches of soil. Poa annua.
Trifolium repens. (Clover)

46
Q

How to treat weeds in a lawn?

A

Control by removing by hand with a daisy grubber.
Apply selective herbicide. 2,4 D. which only kills broad leaved plants not grass.
Encourage a thick sward by scarifying, aerating, top dressing and cutting at correct height. Repair bare patches quickly.

47
Q

List 8 types of equipment used for the removal of weeds.

A
  1. Dutch hoe
  2. Draw hoe
  3. Fork
  4. Spade
  5. Hand tools
  6. Rotavator
  7. Mulching materials
  8. Spray equipment and associated PPE used to apply herbicides. (Mask, goggles, overalls, gloves).

R2103 Plant Health (5 decks)

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