Lakebed Plant Management Suggestions and Recommendations<\/p>\n
For: Property owners and land managers of Lake Delhi<\/p>\n
Prepared by: Dan Kirby, Iowa DNR Fisheries Biologist (M.S., Wildlife and Fisheries Science \u2013 South Dakota State<\/p>\n
University; Iowa Category 5 licensed pesticide applicator\u2013 aquatic pest control)<\/p>\n
Step 1: Identify the plants and identify the problem<\/p>\n
Terrestrial plants growing in the lakebed of Lake Delhi during this extended draw-down are providing benefits\u00a0and challenges to Lake Delhi property owners. Benefits of plants include: stabilization of soils in the lakebed,\u00a0reduced bank and lakebed erosion, reduced sediment delivery to the Maquoketa River, habitat for wildlife, and\u00a0habitat for fish. Potential problems associated with lakebed plants include: plants are unsightly to some owners\u00a0and visitors, views may be obstructed by tall plants, future water travel lanes may be obstructed by woody\u00a0plants if left untreated.<\/p>\n
Some Lake Delhi residents have expressed concerns about increased lake sedimentation and organic matter\u00a0accumulation from plant growth, and these concerns are certainly worthy of monitoring. However, it is my\u00a0opinion that herbaceous plants (grasses and forbs) are unlikely to cause significant long-term impacts to lakebed\u00a0sediments. Increased channel roughness and decreased water velocity associated with terrestrial plants in\u00a0lake beds does temporarily increase the sediment trapping efficiency of reservoirs. This phenomena lasts only as\u00a0long as the plants persist, and that is not very long (days to weeks) for most fully submerged herbaceous land\u00a0plants. Terrestrial plants contribute to the organic matter in lake sediments after reservoirs are filled, but this\u00a0contribution should be viewed in perspective to other inputs of sediment and matter. An Iowa cornfield or\u00a0switchgrass field produces about 6 tons of dry matter per acre and we can expect similar production per acre of\u00a0\u201cweeds\u201d in the lakebed. This means that about 2,400 tons of organic matter could be produced annually on the\u00a0dry areas of the Lake Delhi lakebed. This sounds like a lot of material and it is, but keep in mind that it is a\u00a0fraction of the material delivered by the Maquoketa River during an \u201caverage year\u201d (estimates are typically\u00a0about 60,000 tons per year).<\/p>\n
I recommend that landowners concentrate on suppression of woody vegetation such as willows and\u00a0cottonwoods in areas that will be used as travel corridors for boats, docking areas, or swimming areas. Willow\u00a0trees are more persistent than herbaceous plants after being submerged and could potentially persist for\u00a0months or years after being submerged (depending on stem size). Annual weeds such as giant ragweed,\u00a0smartweed, and barnyard grass are common early invaders of wet areas but they are unlikely to cause any\u00a0significant long-term environmental or infrastructure problems. Perennial moist soil plants such as Reed Canary\u00a0Grass and Fowl Mana Grass are common secondary invaders of wet areas, but they too are unlikely to cause\u00a0long-term infrastructure problems.<\/p>\n
Step 2: Identify the treatment<\/p>\n
If landowners determine that they do have problematic vegetation they have a variety of options for dealing\u00a0with that vegetation.<\/p>\n
1) Mowing. Mowing is an effective method of controlling woody vegetation (e.g., willow trees) and\u00a0annual weeds. Mowing typically favors perennial herbaceous vegetation (e.g., Reed Canary Grass).<\/p>\n
Pros: maintain erosion control provided by plant roots, low potential for environmental impacts, very\u00a0effective control for woody vegetation. Cons: requires access with power equipment or hand tools,\u00a0usually requires at least one treatment per year<\/p>\n
2) Herbicides. Herbicides provide effective treatment of woody vegetation, annual plants, and perennial<\/p>\n
plants. When using any herbicide it is important to understand the personal and environmental hazards\u00a0associated with the herbicide. It is also important to precisely identify problematic plants because\u00a0herbicide effectiveness varies among species. Private individuals without a Category 5 pesticide\u00a0applicators license and appropriate permits cannot use herbicides to treat water bodies such as the\u00a0Maquoketa River. However, private landowners can use herbicides to control vegetation on terrestrial\u00a0areas of Lake Delhi under their ownership as long as they follow all label directions. Contact herbicides\u00a0(e.g., glyphosate) are typically preferred over persistent herbicides (e.g., pendimethalin) when treating\u00a0plants in sensitive areas such as the banks and bed of Lake Delhi. Some popular herbicides (e.g.,\u00a0Roundup) are labeled for use on terrestrial area, but are illegal to use over water due to potential\u00a0environmental contamination. In some cases there are aquatic approved alternatives (e.g., Rodeo) to\u00a0herbicide formulations not approved for aquatic areas (e.g., Roundup). I recommend that landowners\u00a0considering the use of herbicide in or near the lake bed of Lake Delhi consult with a professional\u00a0knowledgeable about herbicides before applying the chemical. Most agricultural cooperatives or farm\u00a0service providers have staff that is extremely knowledgeable about herbicides. Online resources are\u00a0available for herbicide labels and general information. Pros: can effectively control a broad spectrum of\u00a0problematic vegetation, less labor intensive than other methods. Cons: requires access with power\u00a0equipment or hand tools, usually requires at least one treatment per year, best accomplished by\u00a0professionals with proper protective equipment and intimate knowledge of herbicides.<\/p>\n
3) Disturbance (tillage or cultivation). Tillage or cultivation is a common agricultural practice that\u00a0effectively controls annual and perennial vegetation. Tillage systems are most effective for controlling\u00a0perennial plants with a long life cycle (e.g., trees) and least effective for annual plants \u201cweeds\u201d with a\u00a0short life cycle. Pros: can effectively control perennial vegetation without the use of chemicals or\u00a0mowing. Cons: \u201cloosens\u201d soils and will increase soil erosion and sediment delivery to the Maquoketa\u00a0River, requires access with power equipment, usually requires at least one treatment per year, not\u00a0feasible with hand tools.<\/p>\n
4) Planting a cover crop. Cover crops protect sensitive areas from invasion by unwanted plants while\u00a0providing soil erosion protection. Oats are an example of a common cover crop that can effectively\u00a0reduce the presence of annual \u201cweeds\u201d while providing additional benefits. Pros: provides\u00a0environmental benefits through improved sediment retention. Cons: difficult to establish at this stage\u00a0without tillage or herbicide treatment, may require access with power equipment or hand tools,\u00a0typically provides incomplete coverage of affected area.<\/p>\n
5) Fire. Fire is an effective method of controlling woody vegetation and typically favors deep-rooted grass\u00a0species. Controlled burns are best performed by trained professionals and should be coordinated with\u00a0neighbors and the local fire department Pros: can effectively control woody vegetation without the use\u00a0of chemicals or mowing, maintain erosion control provided by plant roots, does not require access with\u00a0power equipment or hand tools. Cons: fire is unpredictable, can only be accomplished in dormant\u00a0season, requires the presence of adequate fuel to carry the fire, typically provides incomplete coverage\u00a0of affected area.<\/p>\n","protected":false},"excerpt":{"rendered":"
Lakebed Plant Management Suggestions and Recommendations For: Property owners and land managers of Lake Delhi Prepared by: Dan Kirby, Iowa DNR Fisheries Biologist (M.S., Wildlife and Fisheries Science \u2013 South Dakota State University; Iowa Category 5 licensed pesticide applicator\u2013 aquatic … Continue reading