Integrated Weed Management

1
Integrated Weed Management
2
What Is a Weed?

• Any plant that is a hazard, nuisance, or causes
  injury to man, his animals, or his desired crops.
  

3
How Weeds Are Troublesome

• Parasitism - Plant obtains resources directly
  from another plant

4
How Weeds Are Troublesome

• Allelopathy Release of compounds from one plant
  that are phytotoxic to other plants

5
How Weeds Are Troublesome

• Allelopathy
• Examples
• Black walnut -Barley
• Purslane -Rye
• Ragweed -Sorghum
• Crabgrass -Wheat

6
How Weeds Are Troublesome

• Competition Plants seek resource(s) that are
  available in limited supply

7
How Weeds Are Troublesome

• Compete with crop for
• Light
• Water
• Nutrients
• CO2
• Space
• Alternative hosts
• Insects
• Diseases

8
Competitive Index (CI)

• Species CI Species CI
• Cocklebur 5.5 Velvetleaf 4.2
• Kochia 2.5 Waterhemp 2.5
• Lambsquarter 1.5 Barnyardgrass 0.3
• Nightshade sp. 3.5 Crabgrass 0.5
• Pigweed 2.5 Fall Panicum 0.4
• Ragweed 4.5 Foxtail 1.0
• Smartweed 1.5 Sandbur 0.4

9
How Weeds Are Troublesome-Alternative Hosts-

• Disease Verticillium wilt
• Hosts Velvetleaf, Nightshades

10
Verticillium Wilt Susceptible Plants

• Acer, Aesculus, Amelanchier, Berberis, Buxus,
  Catalpa, Cercis, Cotinus, Eleagnus angustifolia,
  Fraxinus, Gymnocladus, Ligustrum, Liriodendron
  tulipifera, Lonicera, Magnolia, Prunus,
  Rhododendron, Rhus, Robinia, Rosa, Spriaea,
  Syringa, Ulmus, Viburnum, Weigela

11
How Weeds Are Troublesome
Mature Plants
Seed Rain
Emergence
Seedbank
Other Sources (wind, machinery, etc.)
Decay Predation
Other losses (machinery, erosion, etc.)
12
Weed Seed Predation
of seedbank
13
Seed Production Potential

• Redroot Pigweed 230,000
• Common Lambsquarter 38,000
• PA Smartweed 6,500
• Eastern Black Nightshade 40,000
• Giant Foxtail 4,000
• Wooly Cupgrass 40,000

14
Seed Production Potential

• Velvetleaf / m2 Seed produced / plant
• 1 3706
• 5 2152
• 10 1327
• 30 452

15
Dormancy

• Prevention of germination under conditions
  favorable for seedling growth
• Primary dormancy (innate) dormancy present
  following seed shed
• Secondary dormancy (induced) result of
  unfavorable environment

16
Dormancy Mechanisms

• Physical impermeable seed coat
• Physiological growth inhibitors
• Morphological immature embryo

17
Seed Longevity

• Many weed seeds have the potential to survive
  long periods in soil however,
• Majority of seeds are lost within 2-3 years after
  production
• Estimated that 2/3 of seedbank turns over annually

18
Longevity of Seed After Burial
19
Impact of Seedbank on Weed Management

• Levels of inputs to control weeds is directly
  related to seedbank size
• Seed production by weeds needs to be considered
  in management decisions
• What is an acceptable level of seed production?

20
Seedbank Sampling?

• Costly Time Consuming!
• Seedling Emergence Method

21
Annual Weeds

• Summer annuals

22
Annual Weeds

• Winter annuals

23
Biennial Weeds

• 2 year life cycle
• Year 1
• Germinate
• Develop large root systems and compact cluster of
  leaves
• Year 2
• Mature, produce seed, die

24
Perennial Weeds

• Tap roots
• Have multiple buds at the crown region and upper
  portions of the root
• Common dandelion, curly dock
• Species with tap roots tend to be prolific seed
  producers

25
Perennial Weeds

• Creeping roots
• modified roots
• resource gathering
• food storage
• reproduction from buds
• Canada thistle, hemp dogbane, common milkweed,
  field and hedge bindweed

26
Perennial Weeds

• Rhizomes
• underground stems with buds at the nodes that
  produce adventitious roots and shoots
• most perennial monocots and sporophytes spread by
  rhizomes
• quackgrass, wirestem muhly, field horsetail

27
Perennial Weeds

• Tubers
• enlarged storage organs
• formed at the end of rhizomes on some plants
• yellow nutsedge, Jerusalem artichoke

28
Weed Distribution

• Duration of species of species
• Annual 170 34
• Annual or winter annual 40 8
• Annual or biennial 20 4
• Biennial 35 7
• Biennial or perennial 10 2
• Perennial 225 45
• total 500 species 100

29
Integrated Weed Management

• Using all the available tools to manage weeds in
  an economical and environmentally safe manner
• tools
• Biological
• Cultural
• Chemical

30
Biological Control

• Use of a weeds natural enemies for its control
• Purple Loosestrife European Weevil Root Damage
  by larvae

31
Cultural Control

• Stale Seedbed

32
Cultural Control

• Cultivation
• Cover Crops

33
Cultural Control

• Crop Competition
• booster crops competitive ability
• optimize resources
• optimize planting density
• adjust planting dates
• crop rotation
• drip irrigation
• steam sterilization or fumigation

34
Cultural Control

• Mulches

35
Chemical Control

• betasan casoran dacthal
• finale fusilade gallery
• goal kerb lasso
• pendulum princep roundup
• rout sharpshooter snapshot
• surflan treflan etc.
• Always check the label!

36
Herbicides

• preplant / preemergence / postemergence
• foliar applications
• contact vs. systemic
• selective vs. non-selective
• factors affecting uptake
• pubescence
• epicuticular wax
• dew

37
Herbicides

• Soil applied herbicides
• factors influencing effectiveness
• depth of weed seed
• placement / depth of herbicide
• amount of sand / silt / clay / organic matter
• amount and time of rainfall / irrigation

38
Soil Applied Herbicides

• Factors affecting persistence
• microbial degredation
• chemical degredation
• adsorption
• leaching
• volatilization
• photodecomposition

39
Herbicide Injury

• Drift

40
Herbicide Injury

• Carryover
• Crop Stage
• Tank contamination
• Incorrect adjuvant
• Incorrect rate / calibration
• Environment
• temperature
• rain / irrigation
• soil ph
• amount of sun following application

41
Herbicide Injury

• Problems will arise
• Following the label will minimize suprises

42
Grass Weed Identification
leaf blade
ligule
collar region
auricles
leaf sheath
43
Broadleaf Weed Identification
alternate leaves opposite leaves
44
Broadleaf Weed Identification
Ochrea thin paper-like sheath surrounding stem
at leaf axil Found on Wild Buckwheat,
Pennsylvania Smartweed, Ladysthumb Smartweed
45
Barnyardgrass

• Annual
• Leaf sheath blade hairless
• Flattened stem
• No ligule

46
Barnyardgrass

• Flattened stem (cross-section)

47
Yellow Foxtail

• Annual
• Long hairs on upper leaf surface near base of
  leaf blade
• Hairy ligule

48
Giant Foxtail

• Annual
• Larger seedheads that tend to droop
• Upper leaf surface with short bristly hairs
• Hairy ligule

49
Giant Foxtail

• Note hairy ligule, hair on leaf sheath margin,
  and hairs on leaf surface

50
Green Foxtail

• Annual
• Short seedhead
• Hairy ligule
• Leaf surface generally smooth

51
Green Foxtail

• Thin hairy ligule
• Hair on leaf sheath margin

52
Wild Proso Millet

• Annual
• Seedling often looks like corn plant
• Hairy ligule
• Shiny seeds tan to black

53
Wild Proso Millet

• Hairy ligule
• Bristly hairs on leaf sheath margin

54
Large Crabgrass

• Annual
• Membranous ligule
• Smooth stems
• Ability to root at nodes

55
Large Crabgrass

• Membranous ligule
• Leaf blade and sheaths hairy

56
Quackgrass

• Perennial
• Leaf sheath blade nearly hairless
• Short membanous ligule
• Clasping auricles

57
Quackgrass

• Extensive rhizome system from a single plant

58
Wild Buckwheat

• Annual
• Heart shaped pointed leaves
• Triangular seeds
• Ochrea present

59
Wild Buckwheat

• Ochrea (hairless) at leaf axil

60
Ladysthumb Smartweed

• Annual
• Alternate leaf pattern
• Ochrea (papery sheath) with fringe of hairs

61
Ladysthumb Smartweed

• Stem bent back to expose ochrea with a fringe of
  hairs

62
Pennsylvania Smartweed

• Annual
• Alternate leaf pattern
• Ochrea (papery sheath) without a fringe of hairs

63
Pennsylvania Smartweed

• Ochrea (hairless)

64
Field Bindweed

• Perennial
• 3-cornered triangualar leaves
• Deep spreading root system

65
Field Bindweed

• Note leaf shape and flowers

66
Hedge Bindweed

• Perennial
• Leaves tend to be more 5 cornered than field
  bindweed
• Shallow extensive root system

67
Hedge Bindweed

• Extensive but relatively shallow rhizomes lead to
  quickly developing patches of bindweed

68
Eastern Black Nightshade

• Annual
• First leaves have purple undersides
• Similar to pigweed when young but no notch at tip
  of leaf
• Prolific producer of berries that turn from green
  to purple to black

69
Bitter Nightshade

• Perennial
• Produces woody tissue
• Young leaves
• Older leaves
• Berries that turn from green to red

70
Redroot Pigweed

• Annual
• Leaves have small notch at tip
• Petioles generally have purple coloration

71
Prostrate Pigweed

• Annual
• Glossy small leaves
• Red petiole coloration
• Spreads out along soil surface

72
Common Ragweed

• Annual
• Finely divided lacy leaves
• Very thick cotyledons

73
Giant Ragweed

• Annual
• Mature leaves are 3-lobed
• Mature height up to 15 feet

74
Broadleaf Plantain

• Perennial
• Low growing
• Broad, simple leaves
• Common in lawns, often in shaded areas

75
Velvetleaf

• Annual
• Alternate heart shaped leaves with serrated
  margins
• Stem and leaves densely hairy

76
Common Lambsquarters

• Annual
• First 2 leaves are opposite, later leaves are
  alternate
• Cotyledons and leaves covered with white, mealy
  granules

77
Ground Ivy

• Perennial
• Often referred to as creeping charlie
• Small bluish-purple flowers borne in leaf axils

78
Common Purslane

• Annual
• Opposite leaves with each pair rotated around the
  stem 90o from previous pair
• Thick fleshy leaves w/o hair
• Red prostrate stems

79
Pineappleweed

• Annual
• Stems smooth
• Leaves finely divided, smell like pineapple when
  bruised
• Greenish-yellow flowers

80
Common Yellow Woodsorrel

• Perennial or annual
• Stems hairy, may root at joints
• Leaves with long petioles, divided into 3
  heart-shaped leaflets

81
Jimsonweed

• Annual
• Leaves are smooth and alternate
• Hypocotyl (stem below cotyledons) is very hairy
• Plant has unpleasant odor when crushed

82
Jimsonweed

• Seed pod
• Leaf shape
• Large white flowers

83
Carpetweed

• Annual
• Smooth green stems branching along ground forming
  circular mat
• Leaves in circles of 5 or 6 at each joint of stems

84
Common Mouse-ear Chickweed

• Annual
• Pictured left-common, right-mouse-ear
• Petioles with line of hairs on one side

85
Jerusalem Artichoke

• Perennial
• Fibrous roots with rhizomes and tubers at tips
• Hairy stems up to 9 foot
• Leaves very hairy
• 2-3 inch yellow flowers similar to sunflower

86
Jerusalem Artichoke

• Mature plant

87
Jerusalem Artichoke

• Large roots and tubers contain extensive energy
  reserves (hard to kill)

88
Bull Thistle

• Biennial
• First leaves are oval with a rough, bumpy surface
• Adult leaves form rosette, with dense hairs on
  undersides

89
Musk Thistle

• Biennial
• Adult leaves forming rosette with whitish margin
• Dense hairs on leaf upper and lower surfaces

90
Canada Thistle

• Perennial
• Leaves are alternate with crinkled edges and
  spiny margins
• Spreads with rhizomes

91
Canada Thistle

• Note very wavy leaf margin

92
Canada Thistle

• Rhizomes often lead to thick patches