Weeds 2007

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    Weeds 2007 - Presentation Transcript

    1. WEEDS
    2. WHAT IS A WEED?
      • Any plant growing where it is not wanted
    3. What is a weed?
      • “ A plant whose virtues have not yet been discovered.”
      • Ralph Waldo Emerson
    4. Detrimental Effect of Weeds
      • Look unattractive
      • In pots in nurseries
      • In garden displays
      • In lawns
      • May make harvesting difficult
      • Stinging nettles
      • Vine like weeds in harvesting machines
      • Allelopathy
      • Toxic exudates from weeds that affect crop plants
    5. Detrimental Effects of Weeds
      • Competition
      • Weeds compete for surface nutrients
      • Compete for bees
      • Compete for water
      • Compete for light
      • Poisonous or painful
      • To people and animals due to chemical or physical defences e.g. thorns
      • Harbour Pests and Diseases
      • Humidity increased
      • Over-wintering sites/alternative food source
    6. Detrimental Effects of Weeds
      • Disrupt and destroy native eco-systems by competing for light, water, nutrients, physical space etc
      • Approximately 8 species of exotic (i.e. non-native) plants naturalise in NZ per year
      • Of those, approximately 10% will become invasive
    7. Worst weeds around Dunedin?
      • In order of weed score rating
      • #1 worst ecological potential
      • = bomarea
      • then
      • old man’s beard
      • hawthorn
      • blackberry
      • gorse
      • sycamore
      • banana passionfruit
      • Followed by…
      • buddleja
      • ivy
      • Darwin’s barberry
      • broom
      • cotoneaster
      • convolvulus
      • Chilean flame creeper
    8. Benefits of Weeds
      • Add interest/colour to landscapes
      • Increase diversity
      • Edible/herbal remedies
      • Act as subsoilers
      • Access nutrients lower down in the soil profile
      • Stabilise hillsides
      • Act as indicators
      • Act as a green manure
      • Contain beneficial chemicals
      • Provide food for predator adults
      • Are a food source for a range of wildlife
      • Provide shelter
    9.  
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    13. Characteristics of a weed
      • Colonisers of disturbed habitats
      • Reproduce very quickly
      • Huge genetic diversity
      • Seed dormancy
      • Habit/Form
      • Habitat
      • Defence system
      • Resistance to herbicides
      • A wide range of dispersal mechanisms
    14. Reproduction Methods
      • Rhizome
      • Tubers
      • Root or Shoot Segments
      • Bulbs
      • Seeds
      • Stolons
    15. Weed Lifecycles
      • Annual
      • Biennial
      • Perennial
      • Ephemeral
    16. Annuals
      • A plant that completes it’s lifecycles in one calendar year or growing season.
      • Seed  Germination  Growth  Flowering/reproduction  Seed set  Death
      • Annual weeds ensure survival by seed production.
      • E.g. fathen, groundsel, cleavers
    17. Biennials
      • Year 1 Grow from seed and develop strong root systems and cluster of leaves
      • Year 2 Mature, produce seeds and die
      • Biennial weeds ensure survival by seed production
      • E.g. brassicas, shepherd’s purse
    18. Perennial
      • A plant that persists and produces reproductive structures year after year.
      • Reproduces by Seed and Vegetatively.
          • taproots
          • rhizomes
          • creeping stems
          • bulbs/corms
      • E.g. dock, creeping buttercup, couch, oxalis
    19. Ephemeral
      • A plant that completes many lifecycles within one calendar year or growing season. Ephemeral weeds are very short lived.
      • Seed  Germination  Growth  Flowering/reproduction  Seed set  Death
      • Within weeks
      • Ephemeral weeds ensure survival by seed production.
    20. Implication for weed control
        • Suitable control measures
        • Lifecycle stage
      • Annual/ Mowing, cultivation or contact herbicide.
      • Ephemeral Before flowering.
      • Biennial Cultivation or contact herbicide.
      • Preferably in the first year of growth or in the second year before flowering.
      • Perennial Individuals removed, systemic herbicides.
      • Preferably before maturity – in any year before flowering.
      • Remember the saying:
      • “ One year’s seeding
      • means seven year’s weeding!”
      • [1873 Harland & Wilkinson Lancashire Legends 190]
    21. Weeds – adaptations and survival
        • Plant type (life cycle)
        • Plant vigour/Growth rate
        • Weed habit
        • Seed production
        • Seed dispersal
        • Seeding height
        • Physical and chemical defences
        • Root and specialised underground storage systems
        • Herbicide resistance
    22. Weeds – distribution and growth
      • Different environmental conditions favour different patterns of weed distribution and growth.
        • Coastal areas
        • Amenity turf
        • Bush/woodland areas
        • Wetlands
        • Wasteland
        • Garden bed/borders
    23. Categorising Weeds
      • Dicotyledons
      • - Plants which produce two seed leaves. Includes broad leaved weeds
      • Monocotyledons
      • - Plants which produce a single seedling leaf and includes grasses and cereals
      • Many herbicides are selective in their mode of action. I.e. they only kill a certain type of plant
    24. Dicotyledon Source: University of California www.ipm.ucdavis.edu
    25. Monocotyledon
    26. Monocotyledon versus Dicotyledon
      • Broad leaves
      • Net-like pattern of veins in leaf
      • Flower parts in multiples of 3
      • One cotyledon
      • Long, narrow leaves
      • Parallel pattern of veins in leaf
      • Flower parts in multiples of 2, 4 or 5
      • Two cotyledons
    27. Weed Management
        • Cultural control
        • Biological control
        • Chemical control
        • Legal methods to enforce the 3 methods above
        • Combined together =
        • Integrated weed management
    28. Cultural Weed Control
      • Prevention
      • Keep surrounding areas weed free
      • Mow before flowering
      • General hygiene - machinery, tools, mulches
      • Don’t buy in with mulch, compost or plants
      • Cultivation
      • Hand weeding, hoeing, cultivation.
      • Cheap, time consuming.
      • annual/perennial seedlings
      • Heat treatment
      • water or heat/fire
      • annual/perennial seedlings
      • Mulches (organic and inorganic)
      • Suppresses weed growth by eliminating light
      • No light = No weed
      Physical control of weeds
      • Stale Bed Technique
      • Preparing the bed in advance so that the weeds germinate and can be removed before you sow your crop
      • Digging
      • Turn the soil over and bury the weeds upside down - Instant Gratification
        • - Digging when the soil is wet may destroy the soil structure and cause compaction
        • - Some weeds may be slow to decompose and go slimy - don’t replant too soon
        • - Digging will bring weed seeds to the surface
        • - Try digging in the dark!
    29. Mulching
      • Mulches
      • Prevent weeds germinating - excludes light/unsuitable surface
      • Conserve soil moisture - reduces evaporation
      • Prevents rapid fluctuations in soil temperature
      • Reduces winter heat loss from soil (can prevent them from warming thus increasing frost damage)
      • Prevents soils splashes - reduces soil borne fungal diseases
      • Reduces erosion caused by rain run-off (can prevent water getting into the soil)
    30. Organic Mulches
      • Sawdust
      • Bark chips
      • Peat
      • Hay
      • Straw
      • Leaf mould
      • Spent mushroom compost
      • Fowl manure
      • Stable manure
      • Grass clippings
      • Wood shavings
      • Newspaper
    31. Inorganic Mulches
      • Black polythene
      • Woven plastic fabrics/’Weedmat’
      • Gravel
      • Scoria
      • Pebbles
      • Rocks
    32. Biological Control of Weeds
      • The use of insects or diseases to control weeds
      • Biological control does not aim to eliminate the weed but to reduce it to a level where it can be effectively controlled by other methods
    33. Biological Control of Weeds
      • Weeds
      • Weeds are mostly introduced (accidentally or deliberately)
      • They often flourish in NZ because:
      • - of the more favourable climate
      • - insects and disease which naturally control them are not here
      • Biological control
      • Biological control can be initially slow to show any results. However once it is established it costs nothing.
      • The insect damages the host plant only, therefore there are minimal environmental side effects.
      • To control gorse: gorse weevil ( Apion ulicis ) and gorse spider mite ( Tetranychus lintearius )
      • To control Californian thistle : leaf beetle ( Lema cyanella )
      • To control old man’s beard : old man’s beard leaf miner ( Phytomyza vitalbae )
      Examples of Biological Agents
    34. Selection of Biological Agents
      • Scientific testing
      • Host specific
      • MAF permission
      • Quarantine
      • Breeding up
      • Release
      • Assessment
    35. Chemical control of weeds
      • How Herbicides Work
      • Block a Fundamental Growth Process
      • - destroy chlorophyll
      • - stop cell division
      • - stop respiration
      • Cause stunting, unnatural growth, and dry out the plant (desiccant)
    36. Modes of action
      • Contact Herbicides
      • - foliar applied sprays
      • - enter leaves by diffusion entering the xylem
      • - kills the plant at point of spray contact
      • - use on annuals and young perennials
      • e.g. Universal Weed Killer, Preeglone
      • Systemic or Translocated Herbicides
      • - absorbed either through the roots or leaves
      • - the chemical is then translocated or moved about within the plant as it grows
      • e.g. Roundup
    37. Herbicide Selectivity
      • Selective Herbicide
      • - Kills the weeds without harming the desired plants
      • e.g. Lawn weedkillers
      • kill broadleaves and leave grasses
      • e.g. Grasskiller
      • Non-selective herbicides(broad spectrum)
      • - Kills all vegetation for total control
      • - Do not use on lawns
      • e.g. Amitrole, Round-up
    38. What makes a herbicide selective?
      • Herbicide selectivity:
      • Can be a feature of the herbicide
      • - how it is made, active ingredients, different chemical reaction to different types of plants
      • The way we apply it i.e. Timing
    39. Timing of herbicide use
      • Pre-planting
      • - Spray before planting or sowing.
      • - Target is germinating and existing weeds e.g. Round-up
      • Pre-emergence
      • - Spray to control weeds before weeds/crop emerges
      • - Weed free seed bed and reduced competition
      • e.g. Foresite
      • Post-emergence
      • - Spray herbicide after weed/crop emerges
      • - True selective e.g. Yates Grasskiller
    40. Soil acting herbicides
      • Soil acting herbicides are absorbed by weed shoots as they emerge through the soil resulting in weed death
      • Soil acting herbicides that stay in the soil and continue to control weeds for a extended period of time are called ‘Residual Herbicides’
      • Prefix D 12 months
      • Foresite 3 months +
      • DAS 12 months
    41. Integrated Weed Management
      • Using a combination of control methods to get the best results
      • - Cultural
      • - Biological
      • - Chemical
      • Using minimal amount of herbicides
      • Using herbicides safely
      • Promoting plant health
      • Understanding weed lifecycles to enable effective control
    42. Weed management - Example
      • Poor lawn management gives weeds a competitive advantage.
      • Encourage a healthy lawn
      • - regular mowing (little & often)
      • - regular fertilising
      • - Water in dry conditions
      • - Scarifying
      • - Pest & disease control
      • Discourage weeds
      • - choose good quality lawn seed
      • - control weeds in surrounding areas
      • - don’t let weeds flower
      • - don’t buy weeds in
      • Control existing weeds using a combined approach
    43. Weed Books
      • Weed books on close reserve at the Bill Robertson Library
      • Taylor, R. L. (1981). Weeds of roadsides and waste ground in New Zealand . Nelson: Taylor
      • Uprichard, E. A. (1985). A guide to the identification of NZ common weeds in colour . Palmerston North: NZ Weed and Pest Control Society.
      • Taylor, R. L. (1983). Weeds of crops and gardens in New Zealand . Nelson: Taylor
      • Parham, B. E. V; Healy, A. J. (1976). Common weeds in New Zealand . Wellington: D.S.I.R.
    44. References
      • University of California www.ipm.ucdavis.edu

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