Aquatic Plant Management Louis Helfrich, Ph.D. Department of Fisheries & Wildlife Sciences Virginia Tech

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.

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

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

Why weeds? Nutrients, Light

Why weeds? Shallow water Clear water Excess fertility (nutrients) Invasion of exotic weeds American Lotus, Nelumbo lutrea

Fertilization Can you fertilize weeds away? No

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

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

Algae or Turbidity?

 Rooted aquatic plants are distinguished from the algae by the presence of true leaves, stems, roots, and flowers.

Common Floating Plants Watershield Spatterdock, Nuphar advena

Submerged Plants:Exotics

Emerged and Shoreline Plants Cattail Arrowhead

Plant Dominance 1.Algae 2.Turbid water 3.Fertile, P 4.Planktivourous, carp 5.Small zooplankton 6.Ducks & geese 1.Macrophytes 2.Clear water 3.Fertile, less P 4.Predators 5.Large zooplankton 6.No waterfowl

Weed Control Methods Watershed management Physical Biological Chemical

Weed Control: Physical Removal Drain Dredge Dragging Raking Cutting Skimming Harvesting Aeration

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

Herbicides? –Expensive –Short-term –Toxic –Registered –Liability –Dosage –Timing –Fish Kills –Water-use restrictions

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)

Application Timing Early spring Actively growing Cool water Slow decay Pickerel weed, Pontederia

Application Variables Area treated Water depth Water temperature pH Hardness Flow Exchange rates Weed density Weather conditions Suspended particles Arrow Arum, Peltandra virginica

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

Aquatic Problems 1.Water weeds 2.Water quality 3.Muddy water 4.Leaking ponds 5.Nuisance animals 6.Poor fishing 7.Fish kills

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 , posted March 2000

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.

HerbicideIrrigationFishingLivestockSwimmingDrinking Fluridone (Sonar) Glyphosate (Rodeo)00002 Chelated Copper00000 Diquat (Reward)50113 Endothal Aquathal K143 1<25 Aquathal G73140<25 Table 2. Waiting period (days) before using water after application of aquatic herbicides (Helfrich et al. 1996). Giant Salvia, Salvinia molesta, exotic

Watershed Management Why weeds? excess fertility Livestock waste Fertilizer runoff Waterfowl

Water Plant Control Watershed management Physical Biological Chemical –Water dyes –Barley straw

 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.

High Diversity of Aquatic Plant Species Pondweeds, Potamogeton spp.

Algae or Vascular Plant? Chara Algae

Why water weeds? Excess fertility! Livestock waste Crop fertilizer Ducks & geese Shallow water Clear water Bank slope Exotic weeds

Physical controls (1)Water diversion (2)Dilution (3)Dredging (4)Deepening (5)Water level manipulation (6)Bottom sediment covering (7)Light elimination (8)Harvesting

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 They charge $55.00 for 11 pounds of barley straw. Minimum treatment for 1-acre pond costs $110/acre.

Herbicide Selection Copper compounds –algae Flouridone (sonar) –Submersed & floating Glyphosate (rodeo) –emergent 2-4D –submersed Diquat –algae & submersed