4 Apr 2025

Field Evaluations of Diquat for Controlling Submersed Flowering Rush in Lake Pend Oreille, Idaho

Abstract: The invasive plant flowering rush (Butomus umbellatus L.) was first observed in Lake Pend Oreille, Idaho, within the Columbia River basin in 2008, and it covered several hundred hectares by 2016. Dense infestations of this perennial weed destroy native plant communities and seriously degrade fish and wildlife habitat. Sometimes growing as an emergent on saturated soils or in shallow water, the plant also forms persistent submersed stands in deeper water, which is the typical growth form in Lake Pend Oreille. In 2016, field trials evaluated the herbicide diquat dibromide, formulated as the product Reward, for controlling submersed flowering rush. A 4 ha plot in Oden Bay was treated with diquat at a rate of 18.7 L/ha in late summer 2016 and again in 2017 using a subsurface injection method by boat. Water exchange processes were measured in treated plots in 2017 with rhodamine WT dye mixed with the herbicide. Flowering rush shoots were reduced by 87% in 2016 and 29% in 2017. No adverse effects were measured on water quality (temperature, dissolved oxygen, pH, and conductivity). Diquat should be added to the project’s operational management strategy for controlling flowering rush in Lake Pend Oreille.

4 Feb 2025

Beneficial Use of Dredged Material for Submerged Aquatic Vegetation Habitats: Overcoming Challenges and Seeking New Opportunities

Purpose: There is a critical need to maintain and create conditions that are conducive for long-term survival of submerged aquatic vegetation (SAV) habitats, which provide multiple ecosystem services, using dredged material. This technical note (TN) was developed by the US Army Engineer Research and Development Center (ERDC)–Environmental Laboratory (EL) to address the specific challenges US Army Corps of Engineers (USACE) practitioners at the district and division level face that impede the development of beneficial use of dredged material (BUDM) projects to restore, conserve, and expand SAV habitats. Different ways to overcome these challenges and opportunities that should be further explored are also addressed. The information in this TN was synthesized from discussions at a virtual workshop for USACE practitioners.

15 Oct 2024

Vegetation Establishment and Management in USACE Floodwater Detention Basins: Greens Bayou Flood Risk Management Mitigation Project

Abstract: This report documents efforts by the US Army Engineer Research and Development Center (ERDC) in assisting the US Army Corps of Engineers (USACE) Galveston District (SWG) in native vegetation establishment design, propagation, installation, monitoring, and adap-tive management for the mitigation requirements of the Greens Bayou Flood Risk Management Project. Specifically, to provide (1) a vegetation establishment design ensuring development of sustainable native plant communities compatible with flooding and drought events; (2) suitable native aquatic, wetland, and woody plants for project use; (3) implementation of plantings; (4) monitoring and adaptive management; and (5) vegetation establishment reports and an operations and maintenance manual for long-term vegetation management of the project site. The Greens Bayou Project included approximately 3.7 miles of channel conveyance improvements and 138 acres of storm-water basin detention storage to reduce flooding damage by safely storing excess stormwater during heavy rain events and slowly releasing it back into the bayou. The completed basin was designed to hold approximately 1,400 acre-ft, or 538 million gal., of stormwater. Vegetation establishment, monitoring, and adaptive management efforts in the mitigation features discussed herein occurred between 2019 and 2023.

27 Sep 2024

Surveys in Native and Introduced Ranges (2018–2021) for Natural Enemies of Yellow Floating Heart, Nymphoides peltata Kunth

Abstract: Yellow floating heart (Nymphoides peltata), a widespread aquatic invasive plant in the US, is currently under investigation for biological control de-velopment. From 2018 to 2021, we conducted native (Europe: 14 loca-tions; Asia: 80 locations) and introduced (US: 39 locations) range surveys to create a list of candidate agents and collect baseline infestation data for comparison. We genetically characterized populations and determined those most-closely related to US N. peltata were European. However, we found no promising agents in that region, except for previously reported fungal pathogens. In Asia, several herbivores were identified as potential agents based on observed damage in situ and previous literature reports about host specificity. These included three species of Bagous weevils, one of which may be Bagous charbenensi, and an unidentified leaf-mining Hy-drellia fly. During domestic surveys, generalist leaf-cutting caterpillars were common, similar to the native range. A major discovery was the dam-aging fungal pathogen, Septoria villarsiae, isolated from plants in a pri-vate pond in Maine—the first record in the Western hemisphere. The next steps for this program should include preliminary host specificity and im-pact assessments of S. villarsiae, the fruit-feeding Bagous spp. in China and Korea, and the leaf-mining Hydrellia sp. fly from South Korea.

26 Jun 2024

Flowering Rush Control in Hydrodynamic Systems: Part 2: Field Demonstrations for Chemical Control of Flowering Rush

Abstract: A series of 10 water-exchange studies were conducted from 2019 to 2021 at two sites, Clover Island and Osprey Point, within the McNary Pool of the Columbia River on the Oregon-Washington border. Six of the studies incorporated a barrier curtain or bubble curtain, whereas the other four studies did not include any device to mitigate water exchange. Once annually, diquat aquatic herbicide was applied concurrently with rhodamine water tracing (RWT) dye at the Osprey Point site (2019–2021) to control flowering rush. An additional plot, Clover Island Reference, served as the nontreated control to the Osprey Point treatment plot. Pre- and posttreatment vegetation surveys were conducted in 2019, 2020, and 2021 to determine flowering rush control, treatment impacts to water quality, and nontarget species response. This study sought to (1) document the use of barrier curtains and bubble curtains as potential methods for reducing water exchange and increasing herbicide concentration exposure times within potential flowering rush treatment areas, (2) evaluate bulk water exchange and selective control of flowering rush under varying reservoir operations, and (3) use the results from these studies to provide guidance for managing submersed flowering rush infestations on the McNary Pool, Columbia River, and similar run-of-the-river impoundments.

18 Jun 2024

Initial Rearing, Release, and Establishment of Biological Control Agent Pseudophilothrips ichini to Control Brazilian Peppertree (Schinus terebinthifolia) in South Texas Ecosystem Restoration Projects

Abstract: Control of the invasive Brazilian peppertree (Schinus terebinthifolia) is a major cost component of US Army Corps of Engineers (USACE) ecosystem restoration (ER) projects in South Texas, specifically the USACE Galveston district (SWG) Resacas at Brownsville, Texas, ER Project. Biological control has been developed as a sustainable tool to lower long-term weed management costs. Although a biological control program for S. terebinthifolia has been in operation in Florida since 2019, no similar program existed in Texas until initiated by the Engineer Research and Development Center (ERDC) in 2020. Since 2021, the biological control agent Pseudophilothrips ichini has been reared at ERDC. This technical report details rearing, release, and establishment efforts from fall 2020 to spring 2023 to provide control of S. terebinthifolia in South Texas USACE ER project locations. Initial observations on impact and potential limitations to biological control in hot climates such as those of South Texas are also discussed.

25 Aug 2023

Wildrice (Zizania palustris; Manoomin) Biology, Functions and Values, and Soil Physiochemical Properties Affecting Production: A Review of Available Literature

Abstract: Wildrice (Zizania palustris L.) is an annual aquatic emergent plant primarily distributed across portions of Minnesota, Wisconsin, Michigan, and Canada. Wildrice requires narrow environmental conditions that vary throughout its life cycle. Environmental conditions required include water levels between 15 and 90 cm, slow flowing water, anaerobic soil, and circum-neutral pH. Wildrice production and abundance is most often limited by nitrogen availability. Both short- and long-term changes in local conditions impact distribution and abundance of wildrice at local and regional scales. Reported declines in wildrice production have increased interest in evaluating changing environmental conditions, specifically within the Upper Peninsula of Michigan. Wildrice, or manoomin, is an important food and cultural resource, and remains important to native peoples throughout the region, including the Lac Vieux Desert Band of Lake Superior Chippewa Indians. This report provides a review of literature related to wildrice and examines potential factors affecting its production in the Upper Peninsula of Michigan. This report highlights cultural and traditional values, functions and values of wildrice, and unique chemical and physical aspects of the environment where wildrice grow. Additionally, this report synthesizes the data gathered in the literature review, identifies knowledge gaps, and provides research opportunities for improved wildrice production in the Great Lakes region.

11 Aug 2023

Dredged Material Can Benefit Submerged Aquatic Vegetation (SAV) Habitats

Purpose: This technical note (TN) was developed by the US Army Engineer Research and Development Center–Environmental Laboratory (ERDC-EL) to provide an overview of the ecosystem services delivered by submerged aquatic vegetation (SAV) to estuarine and coastal ecosystems and to describe potential methods for the beneficial use of dredged material (BUDM) to aid in SAV restoration. Although dredging tends to have a negative association with SAV habitats, BUDM may provide an opportunity to expand suitable SAV habitat to areas where depth is the primary limiting factor. Recent in situ observations have shown that SAV has opportunistically colonized several dredged-material placement sites. This TN provides context on BUDM for SAV habitat restoration to encourage increased strategic placement.

31 May 2023

Small Plot Applications of Florpyrauxifen –Benzyl (Procellacor SC™) for Control of Monoecious Hydrilla in Roanoke Rapids Lake, NC

Abstract: Four demonstration plots were selected at Roanoke Rapids Lake, NC to evaluate water exchange and aqueous herbicide residues in stands of submersed aquatic vegetation (SAV) following treatment with rhodamine wt dye and florpyrauxifen-benzyl to control monecious hydrilla. Florpyrauxifen-benzyl (Procellacor™ SC) was applied in combination with Rhodamine WT (RWT) at two of the plots. Dye measurements and herbicide residue samples were collected at specific time intervals to draw comparisons between herbicide and RWT dye dissipation. The two additional plots served as reference plots to the treatment plots. Pre- and post-treatment vegetation surveys were conducted to evaluate monoecious hydrilla control and non-target species response. RWT dye and herbicide residue data indicated rapid water exchange was occurring with each treatment plot. As a result, florpyrauxifen-benzyl concentration and exposure times (CETs) towards monoecious hydrilla were not sufficient to achieve adequate control by 4 weeks after treatment (WAT). To reduce the impact of hydraulic complexity and improve herbicide efficacy, treatments should coincide with minimal reservoir discharge events to extend herbicide CET relationships. Evaluations of florpyrauxifen-benzyl on late season, mature plants may have impacted herbicide efficacy. Evaluations should be conducted earlier in the growing season, on young, actively growing plants, to discern potential differences in efficacy due to treatment timing and phenology. More information on herbicide concentration and exposure time relationships for monoecious hydrilla should be developed in growth chamber and mesocosm settings to improve species selective management of monoecious hydrilla in hydrodynamic reservoirs.

16 Sep 2022

Flowering Rush Control in Hydrodynamic Systems: Part 1: Water Exchange Processes

Abstract: In 2018, field trials evaluated water-exchange processes using rhodamine WT dye to provide guidance on the effective management of flowering rush (Butomus umbellatus L.) at McNary Dam and Reservoir (Wallula Lake, 15,700 ha). Additional evaluations determined the effectiveness of BubbleTubing (hereafter referred to as bubble curtain) at reducing water exchange within potential flowering rush treatment areas. Dye readings were collected from multiple sampling points at specific time intervals until a dye half-life could be determined. Whole-plot dye half-lives at sites without bubble curtain ranged 0.56–6.7 h. In slower water-exchange sites (≥2.6 h dye half-life), the herbicide diquat should have a sufficient contact time to significantly reduce flowering rush aboveground biomass. Other sites demonstrated very rapid water exchange (<1.5 h dye half-life), likely too rapid to effectively control flowering rush using chemical treatments without the use of a barrier or curtain to slow water exchange. At one site, the use of the bubble curtain increased the dye half-life from 3.8 h with no curtain to 7.6 and 7.1 h with a bubble curtain. The bubble curtain’s ability to slow water exchange will provide improved chemical control and increase the potential for other chemical products to be effectively used.