Aquatic Plant Management

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Aquatic Plant Management

• Louis Helfrich, Ph.D.
• Department of Fisheries Wildlife Sciences
• Virginia Tech

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Plants Problem or Benefit?

• Photosynthesis by aquatic plants, both algae and
  rooted water plants, represents the major source
  - contributing from 70 to 90 of the dissolved
  oxygen. Aquatic plants can trap excessive
  nutrients and detoxify chemicals. Aquatic
  wildflowers such as the water lily are sold and
  planted to provide floral beauty in water
  gardens.

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Plants serve as nursery habitat and the
foundation of the aquatic food chain. They
provide food, dissolved oxygen, and spawning and
nesting habitat for fish and waterfowl.

• Wildlife
• Food
• Nursery
• Shelter
• Critical habitat

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Too many plants! A weed is simply a very
successful competitor for space, light, and
nutrients.

• Restricted recreation
• Fish kills
• Fish flavor problems
• Pond water odor problems
• Drinking water taste problem
• Stunted fish growth

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Why weeds? Nutrients, Light
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Why weeds?

• Shallow water
• Clear water
• Excess fertility (nutrients)
• Invasion of exotic weeds

American Lotus, Nelumbo lutrea
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FertilizationCan you fertilize weeds away? No
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Aquatic Weed Prevention

• Prevent fertilizer runoff
• Prevent soil erosion
• Do not feed grass clippings
• Do not feed fish and ducks
• Fence livestock
• Steep banks

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• Aquatic plants can be divided into
• (1) algae
• (2) rooted water plants.

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Algae or Turbidity?
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• Rooted aquatic plants are distinguished from the
  algae by the presence of true leaves, stems,
  roots, and flowers.

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Common Floating Plants
Watershield
Spatterdock, Nuphar advena
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Submerged PlantsExotics
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Emerged and Shoreline Plants
Arrowhead
Cattail
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Plant Dominance

• Algae
• Turbid water
• Fertile, P
• Planktivourous, carp
• Small zooplankton
• Ducks geese

• Macrophytes
• Clear water
• Fertile, less P
• Predators
• Large zooplankton
• No waterfowl

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Weed Control Methods

• Watershed management
• Physical
• Biological
• Chemical

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Weed Control Physical Removal

• Drain
• Dredge
• Dragging
• Raking
• Cutting
• Skimming
• Harvesting
• Aeration

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Herbivorous animals

• Fish, geese, and swans
• Nutrient pumps
• Permits for exotic animals

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Herbicides?

• Expensive
• Short-term
• Toxic
• Registered
• Liability
• Dosage
• Timing
• Fish Kills
• Water-use restrictions

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Chemical Control

• Algae
• Copper Sulfate,
• Copper Complex (Cutrine)
• Submerged Weeds
• Diquat (Reward),
• Fluridone (Sonar / Avast),
• 2, 4-D, (Aqua-Kleen)
• Endothal (Aquathol K)
• Floating (Duckweed and Watermeal)
• Diquat,
• Fluridone
• Emergent and floating Plants
• Endothal, Fluridone, 2,4-D
• Glyphosate (Rodeo)

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Application Timing

• Early spring
• Actively growing
• Cool water
• Slow decay

Pickerel weed, Pontederia
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Application Variables

• Area treated
• Water depth
• Water temperature
• pH
• Hardness
• Flow Exchange rates
• Weed density
• Weather conditions
• Suspended particles

Arrow Arum, Peltandra virginica
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Chemical Control

• 1/3 of pond at a time
• Follow label
• Observe waiting periods

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Aquatic Problems

• Water weeds
• Water quality
• Muddy water
• Leaking ponds
• Nuisance animals
• Poor fishing
• Fish kills

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http//aquat1.ifas.ufl.edu/welcome.html
Control Methods For Aquatic Plants in Ponds and
Lakes Authors L. A. Helfrich, R.J. Neves, G.
Libey, and T. Newcomb, Extension Specialists,
Fisheries and Wildlife Sciences, Virginia Tech
Publication Number 420-251, posted March 2000
http//www.ext.vt.edu/pubs/fisheries/420-251/420-2
51.html
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The density of aquatic plants (both algae and
rooted macrophytes) is largely a function of (1)
nutrient concentrations (phosphorous and
nitrogen) and, (2) light. In general,
nutrient-rich, shallow lakes experience greater
nuisance water weed problems than nutrient-poor,
deep lakes.
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Table 2. Waiting period (days) before using water
after application of aquatic herbicides
(Helfrich et al. 1996).
Giant Salvia, Salvinia molesta, exotic
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Watershed ManagementWhy weeds? excess fertility

• Livestock waste
• Fertilizer runoff
• Waterfowl

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Water Plant Controlhttp//www.ext.vt.edu/pubs/fis
heries/420-251/420-251.html

• Watershed management
• Physical
• Biological
• Chemical
• Water dyes
• Barley straw

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• Aquatic plants can be divided into (1) algae and,
  (2) rooted water plants. Algae are primitive,
  simple plants which lack true roots, leaves, or
  flowers and reproduce by spores, cell division,
  and fragmentation. They range in form from
  unicellular (single cells), through colonial and
  filamentous types, to advanced forms which
  resemble the higher aquatic plants. Some are
  microscopic, but impart green color to the water,
  others are visible as surface films or bottom
  dwelling forms which are often confused with
  higher aquatic plants.

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High Diversity of Aquatic Plant Species
Pondweeds, Potamogeton spp.
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Algae or Vascular Plant?
Chara Algae
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Why water weeds?Excess fertility!

• Livestock waste
• Crop fertilizer
• Ducks geese
• Shallow water
• Clear water
• Bank slope
• Exotic weeds

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Physical controls

• Water diversion
• Dilution
• Dredging
• Deepening
• Water level manipulation
• Bottom sediment covering
• Light elimination
• Harvesting

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Barley Straw?

• The rate is 2-50 grams/square meter
• 1 acre pond 4046 m2 of water
• Therefore, treatment of 1 acre pond at the
  lowest recommended dose, 2 grams would require
  8092 grams or 17.8 pounds of straw.
• Source Aquatic Ecosystems 1-877-347-4788. They
  charge 55.00 for 11 pounds of barley straw.
• Minimum treatment for 1-acre pond costs
  110/acre.

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Herbicide Selection

• Copper compounds
• algae
• Flouridone (sonar)
• Submersed floating
• Glyphosate (rodeo)
• emergent
• 2-4D
• submersed
• Diquat
• algae submersed