Invasive plants in wetlands and their control

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Invasive plants in wetlandsand their control

• Neil Anderson
• University of Minnesota
• ander044_at_umn.edu

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Early detection rapid response

• Early Detection
• Surveillance
• Monitoring
• Control
• Rapid response
• Goal Prevent new introductions

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Early detectionAssessmentvegetation surveys

• Used for
• Monitoring for potential invasives
• Assess effectiveness of vegetation management
  techniques used
• Document rare/endangered species
• Methods
• Garmin hand-held units (above-water)
• Under-water technologies (Trimble units)
• Cameras,
• Geographic positioning system or GPS mapping with
  ESRI ArcGIS software
• Positive plant identification

http//www.aquaticcontroltech.com/index.html
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Water quality surveys

• One-time vs. scheduled monitoring
• Types in-lake, storm water, tributary sampling
• On-site measurements temperature, dissolved
  oxygen, water quality
• Analysis laboratory pH, total alkalinity, N/P
  series, turbidity, color, bacteria

http//www.aquaticcontroltech.com/index.html
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Bathymetric surveys

• Map of water depths
• Necessary for determining type(s) of control
  methods
• e.g. for a drawdown bathymetry map will
  calculate water volume and exposed area during
  drawdown
• For chemical treatment accurate water depths,
  volumetric data to calculate herbicide
  application amounts

http//www.aquaticcontroltech.com/index.html
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Wildlife habitat surveys

• May be needed for permitting compliance
• Regulatory agencies

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Control Methods

• Mechanical
• Physical
• Biological
• Chemical
• Site Modification
• Disturbance Regime
• Ecological Controls
• Prevention
• Education

Risky Business Invasive species management on
National Forests A review and summary of needed
changes in current plans, policies and programs
(www.kettlerange.org/weeds/)
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Mechanical methods

• Hand-pulling
• Special tools may be required, e.g. Weed Wrench
  (New Tribe, 5517 Riverbanks Rd., Grants Pass, OR
  97527)
• Use the best tool(s) for the species

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Lythrum salicaria removal in the 1930s
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Hand pulling by divers

• Used when plant density is low or intermixed
  invasive and desirable species
• May be used with mechanical harvesting, if water
  edges are not deep enough for diving

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Effectiveness of hand pullingMyriophyllum

• 3-year study
• While numbers of plants pulled were 3x greater
  each year, milfoil reproduction was exponential
  (10x greater/yr)

(http//www.dudleypond.org/Milfoil_Report_for_2006
_for_ConCom.pdf)
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Mechanicalcutting, harvesting

• Effective for "area selective" control of
  invasive aquatics clearing or cutting through
  large populations
• May enhance access for boating, fishing, swimming
• Works for all plant species, but best for those
  with a dense surface canopy or those annuals with
  high seed production (Trapa, water chestnut).
• Disadvantages?

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Mechanical raking,Hydro raking

• A floating barge with a backhoe, rake
• Effective technique for selective removal of
  rooted vegetation
• Can clear debris, e.g. muck, peat, decaying
  leaves
• Hydraulic paddle wheel for propulsion
• Can operate in water 0.3 m to 4 m depths
• Duration of control ranges for 1 season
  (Myriophyllum) to 2 yrs or longer for deep
  rooted plants (Typha, Nelumbo)

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Dredging(sediment excavation)

• May provide years of benefit, if done correctly
• Costly!
• Significant ecosystem disturbances
• Requires careful articulation of purpose
• Sufficient deepening of area needed to preclude
  light requirements of rooted plants
• Excavation should not expose inorganic substrates
  that prevent plant recolonization

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Physical methods

• Hot water / steam treatment (wet infra-red)
• Removes waxy cuticles, causing quick death
• Not plant specific
• Enhanced with a surfactant
• Temporary decrease for 1 month
• Waipuna Intl., Carrboro, N. Carolina, USA

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Fountains and Aeration systems

• Aeration, circulation of stagnant water
• Suppresses algae
• Enhance oxygen levels for fisheries

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Weed barriers

• Permeable or Benthic barriers secured to lake
  bottom
• Eliminates rooted plant growth
• Effective, low cost weed control strategy for
  small beachfront areas

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Drawdown

• Lowering water levels
• Requires water control structures to drop water
  levels for extended time periods
• In winter, lowering the water level exposes the
  sediment to freezing, water loss
• Best for species with no overwintering structures
• Negative consequences?

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Chemical methods

• Herbicides
• Broadleaf, grass
• Selective, non-selective
• Modes of action inhibition of electron
  transport, growth regulation (auxin, cytokinin
  mimicry), amino acid synthesis inhibition, lipid
  synthesis inhibition, seedling growth inhibition,
  photosynthesis inhibition, cell membrane
  disruption, and pigment inhibition (Anderson,
  1994)
• General in specificity, side effects, application
  issues
• Hazards

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Registered Aquatic herbicides, USA
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Surfactants, Wetting Agents

• Primarily used as adjuvants with herbicides
• Increase effectiveness of hot water treatments
• May control weeds directly
• (Havey, 1999).

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Biological controls

• Seed bank control (Quarles, 1999, Luken, 1990,
  Luken, 1997)
• Invasives often dominate seed banks
• Factors affecting seed bank quantity, viability,
  quality
• (1) Local vegetation sources
• (2) Seed germination rates
• (3) Seed decay rate, physical destruction of
  seeds
• (4) Seed predation
• (5) Reseeding efforts

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Invertebrate biological controls

• Research and release of agents carries the risk
  that unintended hosts will be attacked and
  decimated
• Not every native plant and growing environment
  can be tested.  Examples
• Natural insect enemies (Hobbs and Humphries,
  1995)
• Introduced invertebrate control species
• Flea beetles (Aphthona spp.) reduces leafy spurge
  (Euphorbia esula)
• Galerucella beetles control some populations of
  purple loosestrife (Lythrum salicaria)
• Musk thistle (Carduus nutans) control with the
  head weevil, Rhinocyllus conicus
• Genetically altered (transgenic or designer)
  insects may eventually be introduced for weed
  control

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Herbaceous fish, insects

• Herbaceous fish control of nuisance plants,
  algae
• Triploid (sterile) grass carp (nonselective)
• Require permitting
• Limited to ponds, small lakes where outflow can
  be blocked
• Herbaceous insects control invasive, submerged
  or emergent aquatic plants
• Milfoil weevil (Euhrychiopsis lecontei)
• Purple loosestrife beetle (Galerucella sp)
• Mixed success

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Biocontrol disadvantages

• Not risk-free, e.g., unanticipated host switching
• Wont establish or control target pest
• Establishes but does not increase or spread on
  its own
• Successful only 16-26 of the time

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Pond dyes

• Blue, black dyes
• Alter sunlight penetration into a lake or pond
• Reduces photosynthetic capacity of plants, algae
• Not recommended for natural ponds
• More suitable for contained, man-made ponds with
  little or no outflow (storm water detention
  ponds, reflecting pond, golf course pond, etc)
• Break down over time
• Periodic reapplication

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Allelopathy

• Production of plant growth, germination
  inhibitors by plants (Aldrich, 1987 Harrison and
  Peterson, 1991)
• Multiple benefits (Schmidt, 1980 Jarvis et. al.,
  1985)
• Controlled allelopathy possible through planting
  of allelopathic plants, application of
  allelopathic chemcals or genetically modifying a
  plant to produce allelopathic substances

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Genetic methods

• Hybridization - Invading species may evolve or
  adapt to a less (or more) pathogenic form over
  time
• Well-adapted invading species are less lethal to
  their host ecosystem, e.g., a parasite that kills
  its host ecosystem is not likely to be successful
• This effect represents an interaction between the
  newly invaded ecosystem as well as within the
  invading organism
• Biologically engineered hybrids - Genetic
  engineering has the potential to change the
  fitness of invading species lethal mutations,
  sterility

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Soil chemistry

• Nutrient availability and cycling to manage
  invasives tend to be less dependent on specific
  soil nutrients
• Soil pH - high or low soil pH depending on
  species, e.g., blueberries and other Ericaceous
  species are acid-loving, whereas species such as
  some bluegrasses, junipers, etc. favor basic
  soils
• Soil amendments can favor desirable species,
  affecting vegetation dominance
• Timing of fertilization encourages certain
  species (Deal, 1966)

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Shading

• Amount, timing of shade
• Duration
• Impact
• Effective vegetation management tool (Elmore,
  1993b).

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Mulching

• Straw mulch (6-8cm) 98 control of yellow
  star-thistle (Centaurea solstitialis) (Dremann
  1996)
• Other types
• Greenwaste materials, cover crops (Elmore, 1996
  Weston, 1996)
• Allelopathic mulching (Putnam and Weston, 1986
  Altieri and Doll. 1978 Quarles, 1999).

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Preventionthe most important tool

• Prioritize new invaders
• Use signage along infested areas to avoid public
  transport
• Seed transport a primary cause of the spread of
  invaders. Prevented by
• 1. Contaminated seeding mixtures (Quarles 1999)
  use only 100 noxious-weed free seed
• 2. Avoid contaminated mulch
• 3. Avoid contaminated topsoil (Quarles, 1999)
• 4. Use quarantines and vehicle washing, e.g., of
  tractors, cattle and logging trucks that may have
  just passed through a weed-infested site and are
  planning to go to a new site
• Eliminate the cause, not the symptoms, of the
  spread of invaders

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Education

• A. Make a list of targeted user groups
• B. Provide weed identification information
  distribution at central locations
• C. Post public relations / media / local displays
  at central locations
• D. Establish a weed sighting report form
• E. Sponsor research projects that study invasive
  species (Morrison, 1997). Projects should include
  a set of study goals replicate sampling
  randomization controls preliminary sampling
  and sampling authentication. Projects might
  include setting thresholds for measurement
  coherent problem questions area division
  appropriate sample sizes data distribution tests.

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Can invasive species be 100 controlled
(eliminated)?

• Yes! Early detection / rapid response
• Mechanical control, e.g. hand-picking of snails
  and hand-pulling of weeds
• Chemical control, e.g. using toxic baits against
  vertebrates and spraying insecticides against
  insect pests
• Biopesticides, e.g. Bacillus thuringiensis (BT)
  sprayed against insect pestssterile male
  releases, usually combined with chemical control
• Habitat management, e.g. grazing and prescribed
  burninghunting of invasive vertebrates.
• No! Phalaris arundinaceavirtually impossible

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References

• Aldrich. R.J. 1987. Interference between crops
  and weeds. In Waller, Allelochemicals Role in
  Agriculture and Forestry. ACS Symposium Series
  No. 330. American Chemical Society, Washington,
  DC., pp. 300 312.
• Altieri, MA. and J.D. Doll. 1978. The potential
  of allelopathy as a tool for weed management in
  crop fields. PANS 24(4)495 - 502.
• Anderson, Sharon D., Director. 1994. Title
  Unknown A web publication of North Dakota State
  University Extension Service, Fargo, ND
  (701/231-7881).
• Biesboer, D., B. Darveaux, W.L. Koukkari. 1994.
  Controlling leafy spurge and Canada thistle by
  competitive species. Final report. Submitted to
  the Minnesota Dept. of Transportation. Office of
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• Daily et al. 1998. Ecosystem services Benefits
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• Deal, EE. 1966. Grasses as lawn weeds. Plants and
  Gardens 22(3)23 - 25.
• Dremann, C.C. 1996. Grasses and mulch control
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• Dunham. R.S. 1973. The Weed Story. Institute of
  Agriculture, University of Minnesota, St. Paul.
  86 pp.
• Elmore, C.L. 1993a. Alternate methods for weed
  management in an urban environment. Preceedings
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  pp. 26-30.
• Elmore, C.L. 1993b. Perennial weeds respond to
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• Elmore, C.L. 1996. The potential for the use of
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• Elmore, C.L. and S.M. Tafoya. 1993. Water savings
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• Friedman, J. 1987. Allelopathy in desert
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• Grossman, J. and W. Quarles. 1992. Strip
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