An update on the control and eradication of water chestnut (Trapa natans, L.) in an Oneonta wetland, 2009 summary report of activities

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1 An update on the control and eradication of water chestnut (Trapa natans, L.) in an Oneonta wetland, 2009 summary report of activities Holly A. Waterfield 1, Willard N. Harman 2, Matthew F. Albright 3 INTRODUCTION The marsh of concern is located within the city of Oneonta, Otsego County, NY. The majority of the shoreline (and site access point) is owned by Louis Blasetti with a number of other landowners along the northwestern shoreline behind Oneida Street. The wetland encompasses about 40 acres of former agricultural bottomland and falls within a remnant oxbow of the Susquehanna River. Beaver activity near the outlet of the wetland influences water level to some degree (Eyres 2009). Water chestnut was first observed in the wetland in 2000, though it is likely that it was introduced in years prior but was not documented. A detailed description and history of the management efforts to control and eradicate the water chestnut (Trapa natans L.) within the marsh is given in a 2009 Master s Thesis submitted by W. Eyres (2009). Management activities included a combination of herbicide applications and hand-pulling of plants in 2006, 2007, 2008 and Details of efforts undertaken in 2009 are presented in this report. Monitoring efforts included visual pre- and post-application assessments of the water chestnut population, and pre- and post-application water chemistry analysis. Management, or control measures, included an herbicide application and hand-harvesting of untreated isolated plant groupings. The herbicide 2,4-D (Navigate ) was applied July 27, 2009 by Allied Biological Inc. Purple loosestrife (Lythrum salicaria) and Galerucella spp. were also observed in Until recently, purple loosestrife was the dominant emergent plant throughout the marsh. Galerucella spp. (leaf-eating beetles) were introduced to the marsh in 2006 by the BFS as a biocontrol agent to reduce and control the loosestrife population. In 2008, purple loosestrife in the northeastern portion of the marsh was heavily damaged by the beetles and produced few inflorescences; plants in the southwestern portion of the marsh remained healthy. In 2009 dead standing loosestrife could be seen from the railroad access; plants were heavily damaged throughout the wetland and inflorescences were rare. In August, new shoots of purple loosestrife could be seen growing up through standing dead loosestrife stems from 2008 (Figure 1). This project will include similar activities through the summer of 2010 and is being conducted with funding from the NYS Department of Environmental Conservation Invasive Species Eradication Grant #T Research Support Specialist: SUNY College at Oneonta Biological Field Station, Cooperstown, NY 2 Director: SUNY College at Oneonta Biological Field Station, Cooperstown, NY 3 Assistant to the Director: SUNY College at Oneonta Biological Field Station, Cooperstown, NY

2 Figure 1. Oneonta marsh, August 28, Late-summer regrowth of purple loosestrife (Lythrum salicaria) following intense herbivory by Galerucella spp. beetles ACTIVITIES AND RESULTS Pre-Application Assessment (20 and 22 July, 2009) On 20 and 22 July the water chestnut population within the marsh was assessed via visual observations and documented with photographs. The most dense plant growth was located in the north and north-eastern portion of the wetland, in the area of sites 18, 22, and 23 (Figure 2). Fruiting bodies were abundant and fairly advanced in development on the vast majority of plants that were inspected; the viability of these fruits is unknown, though the late timing of the herbicide application increases the chance of propagation and potential population expansion in the 2010 growing season. A water sample was collected from the outlet sampling site in the southwestern portion of the wetland off-shore from the access site. The sample was preserved to ph < 2 with sulfuric acid. Analyses were conducted to determine concentrations of total phosphorus (TP), total nitrogen (TN), nitrate+nitrite (nitrate), and ammonia; methods are listed in Table 1. Herbicide Application (July 27, 2009) The herbicide Navigate (EPA # ) was applied at a rate of 200 lbs/acre on the main population of water chestnut (approximately 7.5 acres) by Allied Biological Inc. under a permit issued by the NYS Department of Environmental Conservation (DEC). Figure 3 illustrates the approximate 2009 herbicide application area.

3 Table 1. Methods used in the nutrient analyses of water samples collected at the marsh. Analyte Method Name Reference Total Phosphorus Ascorbic acid method Liao & Martin 2001 following persulfate digestion Total Nitrogen Cadmium reduction following peroxodisulfate digestion Ebina 1983 Pritzlaff 2003 Nitrate+Nitrite Cadmium reduction method Pritzlaff 2003 Ammonia Phenolate Method Liao 2001 Figure 2. Aerial photo of the marsh (Oneonta, NY) with sampling points from past studies and water sample collection locations (figure modified from Eyres 2009). Water sampling locations are indicated; numbers indicate sites that have received herbicide application between 2006 and 2009.

4 Figure 3. The marsh (Oneonta, NY): shaded area illustrates the approximate 2009 herbicide application area (7.5 acres). Figure provided by Allied Biological, Inc. Post-Application Assessments & Hand-Harvesting (14 and 28 August, 7 September 2009) Two weeks after the herbicide application, we returned to the wetland to assess the state of the treated patches of chestnut and to remove (by hand) untreated isolated patches of water chestnut within the wetland. Such isolated clusters were relatively few in number, and were small, comprised of fewer than 10 ramets per clone. Plants within the treated area were visibly unhealthy and in a state of decay below the water surface. As was the case in 2008, the majority of the chestnut population in 2009 was again represented by multiple smaller groups rather than one large patch, though they were not delineated with GPS. Water samples were collected at two sample sites, deep and outlet as shown in Figure 2. Nutrient Dynamics Table 2 summarizes the nutrient data collected before and after the herbicide treatment. Figure 4 provides a comparison of nutrient conditions before and after treatment from 2006 through 2009 ( data from Eyres 2009). Prior to the herbicide treatment, the total phosphorus concentration at the southern end of the wetland (outlet) was 25.5 µg/l, which is consistent with 2007 and 2008 pre-treatment conditions (Eyres 2009). In 2006, a major flood

5 flushed the wetland system, resulting in a decrease in concentrations pre- and post-treatment. Following herbicide treatment the total phosphorus concentration increased to 118 µg/l in the vicinity of the treated water chestnut population, likely indicating a release of phosphorus from the decaying plant materials. The phosphorus concentration was also elevated at the outlet site, though not above the range typically observed in past years prior to herbicide application. Such a spike in phosphorus concentration following the herbicide application has not been observed every year, though one was also documented in 2007 when the concentration went from 12 µg/l before the application to 500 µg/l following (Eyres 2009). Total nitrogen increased at the outlet site following the herbicide treatment, with an initial concentration of 0.37 mg/l prior to treatment and 1.9 mg/l following, while the sampling site closest to the treated plant patches showed no increase in TN. As with phosphorus, this increase was also documented in 2007, but not in 2006 or 2008 (Eyres 2009). Based on the nitrogen analyses, the majority of nitrogen is contained in organic compounds, likely derived from the decomposing plant material. Table 2. Nutrient concentrations at outlet and deep sampling sites in the marsh prior and subsequent to herbicide application (July 27, 2009). Ammonia, nitrate, and total nitrogen are presented in mg/l, total phosphorus in µg/l. Ammonia Nitrate Total Nitrogen Total Phosphorus Sample Date Site mg/l mg/l mg/l ug/l 7/20/2009 Outlet /14/2009 Outlet 0.03 < /14/2009 Deep CONCLUSIONS To date, control efforts have been considered successful, in that less effort is needed to hand-harvest plants outside of the herbicide treatment area. Based on canoe-loads of plant material removed from the wetland, far less biomass exists outside of the herbicide treatment area (10 canoe loads were removed in 2008 compared to the equivalent of a single full canoe in 2009). Overall, the water chestnut population showed considerable decline monitoring will be more intensive, aiming to quantitatively assess the status of the water chestnut population, effectiveness of the herbicide treatments and any associated impacts on water quality.

6 Total Phosphorus Concentration (ug/l) Total Phosphorus Concentration Prior and Subsequent to Herbicide Application pre-appliation post-application Figure 4. Total phosphorus concentration (µg/l) in the northeastern sample collection site (deep) prior and subsequent to herbicide application. Pre-application data for 2006 and 2009 from outlet sample site. REFERENCES APHA, AWWA, WPCF Standard methods for the examination of water and wastewater, 17 th ed. American Public Health Association. Washington, DC. Ebina, J., T. Tsutsui, and T. Shirai Simultaneous determination of total nitrogen and total phosphorus in water using peroxodisulfate oxidation. Water Res. 17(12): Eyres, W Water Chestnut (Trapa natans L.) infestation in the Susquehanna River watershed: population assessment, control and effects. Master s Thesis: SUNY College at Oneonta. Bio. Fld. Sta. OP No. 44. Liao, N Determination of ammonia by flow injection analysis. QuikChem Method J. Lachat Instruments. Loveland, Colorado. Liao, N. and S. Marten Determination of total phosphorus by flow injection analysis (colorimetry acid persulfate digestion method). QuikChem Method F. Lachat Instruments. Loveland, Colorado. Pritzlaff, D Determination of nitrate/nitrite in surface and wastewaters by flow injection analysis. QuikChem Method C. Lachat Instruments, Loveland, Colorado.