2008 Statewide Strategic Plan for Eurasian Watermilfoil in Idaho

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Eurasian watermilfoil control may not occur with heavy snowfall or during milder, rainy winters. Water bodies suitable for drawdown control are those where drawdown occurs on a prolonged and regular basis. Because a drawdown impacts the entire water body, it should be conducted only under the direction of an integrated aquatic vegetation management plan. Except for reservoirs, few water bodies in Idaho have water control structures and the means to lower the water level to the extent necessary to achieve significant Eurasian watermilfoil control. Because impacts to habitat can be dramatic, a drawdown should only be considered for Eurasian watermilfoil control after these impacts are carefully considered by resource agencies. 2. Bottom barrier Barrier material is applied over the lake bottom to prevent plants from growing. Bottom covering materials such as sand-gravel, polyethylene, polypropylene, synthetic rubber, burlap, fiberglass screens, woven polyester, and nylon film have all been used with varying degrees of success (Figure 13). Typically, synthetic (geo-textile) fabrics or burlap are used. Bottom barriers can be used at any depth. Bottom barriers create an immediate open water area. Duration of control depends on a variety of factors, including type of material used, application techniques, and sediment composition. Synthetic materials have eliminated Eurasian watermilfoil for at least the season of application. In some situations, after satisfactory control has been achieved, bottom barriers may be relocated to other areas. Figure 14. Installing bottom barriers Bottom barriers can usually be easily applied to small, confined areas such as around docks, boat launches, or swimming beaches. Bottom barriers are hidden from view and do not interfere with recreation or shoreline use. They can be installed around obstructions. Bottom barriers do not result in significant production of plant fragments, which is advantageous for Eurasian watermilfoil control. Barriers are most appropriately used for localized, small-scale control where exclusion of all plants is desirable. Depending on the material, major drawbacks to the application of bottom barriers include some or all of the following: control not species-specific, expensive if used on a large scale, labor-intensive installation, limited material durability and possible suspension due to water movement or gas accumulation beneath material. Periodic maintenance (yearly) of bottom barrier materials is necessary to remove accumulations of silt and any rooting fragments. Bottom barrier material costs vary depending on the type of material used. 27
Bottom barriers are appropriate in water bodies that have Eurasian watermilfoil lightly scattered singly or in small patches within the littoral zone, around docks where there are no large obstructions and also along short stretches of shoreline. Cost and maintenance of bottom barriers confine them to very small-scale use. Follow-up is essential to ensure success with bottom barriers. Even a few Eurasian watermilfoil fragments left in the water can start a new infestation. Diver and surface inspections should continue at least twice a year during the growing season. Survey work should be as frequent as can be afforded since small Eurasian watermilfoil plants or fragments may be easily overlooked. C. Manual Controls 1. Hand-pulling Hand-pulling and removal of rooted, submerged plants is a labor intensive control method. This method involves digging out the entire plant with its roots. Plants are then deposited in a dry disposal area away from the shoreline. No specialized gear is required in waters less than three feet. In deeper waters, hand pulling is most efficient with divers using snorkeling equipment or SCUBA gear. Divers carry mesh bags to collect plants. Plants must be disposed of on shore. Hand pulling can begin as soon as Eurasian watermilfoil can be easily seen and identified - generally in the spring or as soon as it is discovered in the water body. Sediment type, visibility, and thoroughness in removal of the entire plant, particularly the roots, all affect the efficacy of hand-pulling. A high degree of control, lasting more than one season, is possible when complete plant removal is achieved. Advantages of hand-pulling include immediate clearing of the water column. The technique is selective and is most useful in sensitive areas where disruption must be kept to a minimum. It is a highly labor intensive control option, most appropriate in small or low density areas. Environmental impacts, including turbidity and bottom disruption, are short-term. Hand-pulling is time-consuming and can be costly. Diver visibility may become obscured by the digging process, making it difficult to see and remove roots. Hand-pulling is not practical for large areas. This method is useful for small-area, short-term control of Eurasian watermilfoil around docks and along short shoreline segments. 2. Diver Dredging Divers operate portable dredges with suction heads that remove plants and roots from the sediment - essentially vacuuming the bottom of the lake (Figure 14). The suction hoses draw the plant/sediment slurry up to a small barge or boat carrying the dredge. On the barge, plant parts are separated from the sediment slurry and retained for off-site disposal. The sediment slurry can be returned to the water column. 28
Page 1 and 2: 2008 STATEWIDE STRATEGIC PLAN FOR E
Page 3 and 4: A Statewide Strategic Plan for Eura
Page 5 and 6: I. Introduction In April 2006 the I
Page 7 and 8: V. Idaho Eurasian Watermilfoil Peer
Page 9 and 10: and contractor oversight to effecti
Page 11 and 12: Figure 3. Eurasian watermilfoil sur
Page 13 and 14: • Task 3: Establish appropriate m
Page 15 and 16: appear first. Eastern Idaho should
Page 17 and 18: B. Description A number of milfoil
Page 19 and 20: and boating activities, with each f
Page 21 and 22: the state. The highest priority wee
Page 23 and 24: and provides assistance to cooperat
Page 25 and 26: the boat with a GPS to the predeter
Page 27: IX. Eurasian Watermilfoil Managemen
Page 31 and 32: emaining root masses. Duration of c
Page 33 and 34: Search for a classical biological c
Page 35 and 36: sources of dilution need to be inve
Page 37 and 38: 3. Fluridone Fluridone (Trade names
Page 39 and 40: X. Current Eurasian Watermilfoil Ma
Page 41 and 42: 2007 Total project cost: $19,400 IS
Page 43 and 44: 2007 Total project cost: $82,660 IS
Page 45 and 46: C. Effect of sediment on efficacy o
Page 47 and 48: scientists and weevils could easily
Page 49 and 50: Surveys for pathogens were restrict
Page 51 and 52: Creed Jr., R.P. and S.P. Sheldon. 1
Page 53 and 54: Komarov, V.L. 1929. Flora poluostro
Page 55 and 56: Moody, M.L., Les, D.H. in Press. Di
Page 57 and 58: Westerdahl, H.E. and K.D. Getsinger
Page 59 and 60: as transparent and publicly availab
Page 61 and 62: to amend if they require legal revi
Page 63 and 64: Recommendation 2.3: Program intent
Page 65 and 66: Excessive uncontrolled growth of aq
Page 67 and 68: species or the reduction of their p
Page 69 and 70: Some or many of these techniques ar
Page 71 and 72: ISDA Response: Given that ISDA does
Page 73 and 74: expertise found in warmer climates.
Page 75 and 76: umors and public fear of management
Page 77 and 78: Option How it Works Pros Cons Suita
Page 79 and 80:
Option How it Works Pros Cons Suita
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Option How it Works Pros Cons Suita
Page 83 and 84:
Costs include estimated raw materia
Page 85:
Office Visits Quantity What is the
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2008 Statewide Strategic Plan for Eurasian Watermilfoil in Idaho

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