A Synopsis of the 2014 Hydrilla Treatments on the Erie Canal

Transcription

1 A Synopsis of the 2014 Hydrilla Treatments on the Erie Canal Michael D. Netherland 1, K. Dean Jones 2, Rich Ruby 3, and Mike Greer 3 1 S Army ERDC, Gainesville, FL 2 niversity of Florida, CAIP, Lake Alfred, FL 3 S Army Corps of Engineers, Buffalo District, Buffalo, NY Key Findings: 1 Hydrilla tuber sprouting during the 3 rd week of June, 2014 was synchronous and ~90% of the total tubers had sprouted. All of the plants growing from sprouted tubers were less than 15 cm in length. Overall hydrilla tuber densities in the canal were reduced by >90% based on the October sampling. 2 Following the herbicide treatment on July 23rd, hydrilla biomass in the canal was reduced by 100% in 4 of the downstream sample sites. Despite concerns that hydrilla might recover from tubers that sprouted later in the season; we did not observe any additional sprouting following the July treatment. 3 Hydrilla in the area near the service road ramp (western edge of the treatment area was not controlled by the initial treatment or by a follow up treatment in September targeting this site. 4 Overall hydrilla frequency in the canal was reduced from 33% to ~4% following the treatment. The majority of hydrilla remaining in the canal was present in the service road ramp area described above. 5 Sampling for the herbicide endothall suggested that concentrations moved eastward in the canal at a higher than desired rate following application. This resulted in less than optimal exposure of the hydrilla in the service road ramp area. 6 Native vegetation was significantly impacted by the treatment with all species showing a marked decrease in frequency of occurrence following the July 23 rd application. Background: The invasive submersed plant hydrilla (Hydrilla verticillata L.f. Royle was discovered by S Fish and Wildlife Service (FWS personnel in multiple sites within Tonawanda Creek/Erie Canal near Buffalo, NY in the late summer of Samples of the plant were sent to the SGS lab in Reston, A in 2013 and confirmed as the monoecious biotype of hydrilla. Based on several interagency discussions and additional sampling and delineation efforts conducted in 2013, a plan to control hydrilla in the canal during the summer of 2014 was formulated. The proximity of the infestation to the Niagara River and the potential for further spread of hydrilla eastward through the canal to numerous key water bodies across New York were primary factors that drove the decision to initiate a demonstration control project. The key technical challenge in controlling hydrilla at this site was related to high water flow rates of 400 to 800 CFS (800 to 1600 acre feet/day typically maintained in the canal during the summertime. Given these flow rates, it was decided that use of the slow acting herbicide fluridone was not practical due to the requirement for >60 days of exposure time. As the majority of hydrilla eradication programs have relied on use of fluridone, an alternative strategy was presented to the technical review panel. In working with the NY State Canal Corporation, a plan was devised to reduce flow rates in the canal for a period of 48 hours and to utilize the contact herbicide endothall (Aquathol K TM to control established beds of hydrilla. After reviewing various options for control (including treating 15 miles of the canal at 3 mg/l endothall,

2 the final plan included treating ~ 7 miles of the canal (213 acres with endothall at a concentration of 1.5 mg/l (ppm. Following a 48 hour exposure period, canal flows were to be resumed and the downstream movement of the endothall treated water was expected to control scattered beds of hydrilla in the remaining section of the canal. Figure 1 provides an overview of the project area. Strategies for treating monoecious hydrilla using a contact herbicide: In discussing strategies for treating monoecious hydrilla with a contact herbicide, our effective window was determined to be after the bulk of the tubers had sprouted and prior to the formation of new tubers. It is important to note that the tubers and turions of monoecious hydrilla are the only parts of the plant that persist through the winter months in NY. We established four initial tuber sampling sites in the canal based on the presence of extensive hydrilla beds. The high tuber densities in these sites would allow us to collect enough propagules during each sample event to extrapolate our findings to other areas of the canal that contain varying densities of hydrilla. Based on our initial sampling conducted in 2013, we observed only 7% sprouting in early June and the sprouted propagules had not actually emerged above the sediment. Due to the sparse hydrilla presence at this time, we did not attempt to select permanent sample sites. By the third week of August, 2013 there were dense beds of hydrilla and a limited number of new tubers had started to form (i.e. still attached to the rhizome. We noted a marked increase in both tuber number and number of tubers forming by the fourth week of September (Figure 1. Production of new tubers slowed between late September and early November. During the November sampling event, we pulled up numerous plants to inspect for turion formation, and we did not observe any turions on either rooted plants or on free floating fragments. Sampling during the third week of June, 2014 indicated that tuber sprouting in our designated sample sites ranged from 88 to 93% (Table 1. The multiple tubers collected during these sample events supported small plants (<15 cm in length that had just begun to emerge from the sediment. This high rate of tuber sprouting in the later part of June had several positive implications for the demonstration project including: 1 with ~90% of the tubers sprouting, few propagules remained dormant and available to sprout later in the season; 2 the synchronicity of the sprouting event supported hypotheses that longterm exposures to cold temperatures would stimulate mass sprouting; and 3 synchronous sprouting suggests that contact herbicides have a much better chance to be effective. Biomass sampling: We utilized a rake sampling method recently described by Johnson and Newman (2012 to collect hydrilla biomass in our tuber sampling sites. Biomass samples were collected in July 2014 just prior to treatment and at monthly post-treatment intervals. In four of the sample sites, hydrilla biomass was reduced by 100% (Table 1. Based on our point intercept surveys, we added a 5 th site at the Service Road Ramp area, as poor initial control of hydrilla was noted at this site. Endothall Treatment and Water Sampling Results: Treatment details including the amount of product used, the application sites, public notice and posting, and flow conditions in the canal can be found in a recent report prepared by Ecology and Environment, Inc. for the Corps of Engineers Buffalo District. To summarize, 1855 gallons of endothall were applied to ~ 7 miles of the western end of the canal on 7/22/14 from the highway 425 bridge to the Campbell Road bridge. Water sampling to determine the dispersion and movement of endothall following the treatment was conducted and samples were analyzed the same day to provide a rapid turnaround that would allow for potential adjustments in canal flow rates.

3 Area MC1 MC2 MC3 MC4 MC5 MC6 MC7 MC8 MC9 O1 O2 O3 R1 R2 L1 L2 L3 L4 Acres L4 MC8 * MC7 MC6 L1 MC9 L2 L3 Amherst eterans Canal Park Launch O3 * MC5 North Tonawanda Botanical Gardens Launch MC4 City of North Tonawanda Boat Launch R2 R1 * O2 MC3 MC2 O1 MC1 Legend: Figure 1 Main Channel Treatment Areas (MC1,3, ac Tonawanda Creek Reduced Concentration Treatment Areas (MC2, ac Oxbow Treatment Areas (O ac Erie and Niagara Counties, NY Hydrilla Treatment Areas FIGRE: TREATMENT DATE: MAP DATE: 2 7/22/14 8/13/14 Supplemental Treatment Areas (R1-2, L ac * Loading Areas Miles 11 JOHN ROAD STTON, MASSACHSETTS PHONE: ( FAX: ( WEB:

4 Table 1. Hydrilla tuber sampling was conducted in areas where dense beds of hydrilla were delineated. A total of 20 core samples (4 coring device were collected at each sample site. Site 1 West Canal Park Total Tubers sprouting forming Turions Observed Biomass G dry wt/ m 2 Aug NA Sept NA Nov NA June NA July (18 Aug Sep Oct Site 2 Park East of W. Canal Total Tubers sprouting forming Turions Observed Biomass G dry wt/ m 2 Aug NA Sept NA Nov NA June NA July (27 Aug Sep Oct Site 3 Oxbow East of W. Canal Total Tubers sprouting forming Turions Observed Biomass G dry wt/ m 2 Aug NA Sept NA Nov NA June NA July (14 Aug Sep Oct Site 4 Botanic Garden Total Tubers sprouting forming Turions Observed Biomass G dry wt/ m 2 Aug NA Sept NA Nov NA June NA July (19 Aug Sep Oct Site 5 Service Road Total Tubers sprouting forming Turions Observed Biomass G dry wt/ m 2 Sept NA Oct (13 1 While evidence of sprouting was observed (elongation of the tip, an actual plant hand not emerged above the sediment 2 A small rhizome was noted on a plant, but an actual tuber had not been formed.

5 Endothall results through the first 72 hrs are provided in Figure 2. Endothall concentrations taken at three sites across the canal on the day of treatment indicated rapid dispersion from shoreline treatment areas to the center of the canal (data not shown. Sampling on the day of treatment suggests that endothall was near target concentrations in the treatment block. Water samples taken on 7/23 at 1DAT indicate a pronounced eastward movement of the endothall concentrations (Figure 2. While some product movement was anticipated, this magnitude of dispersion resulted in a situation where sites 3, 4, and 5 (in the treatment block on the western edge of the treatment area near the service road ramp received shorter than desired exposures to diminishing concentrations of endothall. Endothall concentrations from mile 9 to 13 (outside of the application block confirmed a significant eastward movement of endothall. Given the rate of dispersion to the east, the Canal Corporation was contacted following the 1 day sample event and flow was shut down to an absolute minimum. This decision likely prevented the complete clearance of endothall from most of the treatment block during day two. By 2 and 3 DAT, endothall concentrations were more stable at each sample site indicating that flows were no longer moving the herbicide away from the treatment plot. Endothall sampling in the three treated oxbows resulted in maintenance of target concentrations throughout the exposure period. ertical sampling indicated that endothall did not readily disperse to the deepest parts of the main channel. Sampling at the confluence of the canal and river (mile 0 and at 1 and 2 miles into the canal did not result in any detection of endothall. Endothall Conc. ug/l Day of Treatment 1 DAT 2 DAT 3 DAT Mile Mark on Canal Figure 2. Endothall concentrations in the Erie Canal collected at different mile markers within the treated plot (numbers enclosed in the rectangle and downstream of the treated plot. The downstream sample sites (from mile 9 to 15 were part of the overall target area for control of hydrilla beds; however, we relied on flow to move the herbicide into these regions.

6 Point Intercept Sampling for Invasive and Native Plant Frequency: The results for point intercept sampling efforts in the west half of the canal (i.e. the treated area are presented in Table 2. We sampled between 907 and 1026 points along the two shorelines of the western portion of the canal via a rake toss method. Plants were identified to species at each point and density rankings (data not included were also recorded. Sample results for the eastern half of the canal will be presented in a final report. The increase in plant frequency ratings from late June to July indicate that species such as hydrilla and vallisneria were rapidly expanding during this time. Following treatment during the third week of July the subsequent frequency ratings in August, September, and October indicate a marked decrease in all submersed plant species in this section of the canal (Table 2. While the ~89% reduction in hydrilla frequency was encouraging, we observed similar reductions in frequency for submersed native plants. One of the original objectives of this demonstration project was to determine if selective control of hydrilla could be achieved following a large-scale application of endothall. To enhance our ability to achieve this selectivity, we reduced endothall application rates to 1.5 ppm in the west half of the canal (the original plan was for an application of 3.0 mg/l. Despite this reduction in endothall use, we observed strong impacts on all native plants present in the canal. While impacts on plants such as Eurasian watermilfoil, sago pondweed, and naiads were predicted, the impacts on vallisneria and water lily were unexpected. Additional sampling in June and July 2015 will determine recovery of native vegetation along the shorelines of the canal. In terms of post-treatment observations for hydrilla, the majority of plants were located from the highway 425 bridge to the service road ramp. This large contiguous bed remained intact following the limited endothall exposure achieved with the July treatment. Sampling during August indicated the presence of dense beds that were starting to produce rhizomes and tubers. If the sample points in this specific area of the canal were to be removed from the frequency ratings, hydrilla frequency in the western section of the canal would be reduced to < 2%. We did not find any hydrilla in the eastern section of the canal following the herbicide application. Based on the success in hydrilla reduction in other portions of the canal, an additional treatment was planned to target hydrilla in the service road ramp area. Targeting hydrilla in a discrete area of the canal: Details of the 2 nd application are included in the report from E&E mentioned above. To summarize, on September 16, 2014, a total of 261 gallons of endothall were applied to 26 acres from the bridge east of Route 384 to just east of the Service Road Ramp (Figure 3. Water samples were collected to determine product retention and movement. The Canal Corporation was managing the system to minimize flows and create a low-flow treatment situation for 24 hours. Water sampling was initiated following the treatment via the establishment of sample sites both within and outside of the treatment block. Sites labeled Ref 0 and Ref 1 were west of the treatment plot and sites labeled Ref 2 through 10 were located east of the treatment plot (Figure 4. Results suggest an eastward movement of the endothall with rapid clearance by 26 hours after treatment (Table 3. While the herbicide was applied to the near-shore areas (up to 10 ft contours, rapid lateral dispersion across the canal was noted within hours of application. The herbicide moved eastward from the treatment block within the first day and significant endothall concentrations were noted at reference sites 2 through 5 at the 5 and 21 hour sample periods. Endothall concentrations in Treatment sites 1 and 2 were significantly lower by 5 and 21 hours post-treatment. Treatment site 3 at the east end of the plot maintained endothall

7 concentrations near the target rate through 21 hours post application. Once the Canal Corporation resumed normal flows at ~24 hours, we noted rapid loss of herbicide from all of the treatment plots and significant dilution of the endothall concentrations in the downstream stations east of the treatment plot. Table 2. Summary of point intercept data collected for the Erie Canal within the target application zone. Percent frequency results: Erie Canal from the River to Campbell Rd. Bridge Jun 14 Jul 1 14 Aug 14 Sep 14 Oct 14 Exotic submersed macrophytes (% Hydrilla (Hydrila verticillata Eurasian watermilfoil (Myriophyllum spicatum Water Chestnut (Trapa natans Native submersed macrophytes (% coontail (Ceratophyllum demersum elodea (Elodea canadensis naiad (Najas minor Potamogeton species (Potamogeton sago pondweed (Stukenia pectinata wild celery (allisneria americana water star-grass (Zosterella dubia Native floating-leaf macrophytes (% fragrant water-lily (Nymphaea odorata Number of sample points Oxbows were not sampled in July and August.

8 Path: L:\Buffalo\Tonawanda_Creek\Maps\MXD\Treatment_Areas\2014_Sept04\Spot_Treatment_Areas_ mxd Figure 3 Spot Treatment Area and One-Half Mile Buffer Tonawanda Creek Erie and Niagara Counties, New York e e Av Payn Legend * Boat Launch Spot Treatment Area One-Half Mile Buffer Niagara County County Boundary Secondary Road Webste r St 384 Local Road t ont S Trem Sweeney St 425 Service Drive Boat Launch * 265 Main St 266 Erie County SCALE Miles SORCE: ESRI 2011; Ecology and Environment, Inc. 2014; S Army CORPS of Engineers, 2014 Service Layer Credits: Source: Esri, DigitalGlobe, GeoEye, icubed, Earthstar Geographics, CNES/Airbus DS, SDA, SGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS ser Community 2014 Ecology and Environment, Inc.

9 Path: L:\Buffalo\Tonawanda_Creek\Maps\MXD\Sampling_Locations\2014_Nov04\Water_Sampling_Locations_ mxd Pa yn ea ve Figure 4 Ref10 ing ect lvd Conn B Rd Tonawanda Creek Erie and Niagara Counties, New York na To Meadow Dr reek wanda C Lockport Ave Spot Treatment Water Sampling Locations Ref9 Nash Rd Legend Ref8 Samples collected outside of the treatment area Samples collected within the treatment area Old Walck Rd vd s Bl Fall Spot Treatment Area 425 at Whe field St Major Road Secondary Road Ref7 gar a Old Ni a d Falls Blv 429 County Boundary 62 Niagara County Local Road E Robinson Rd N French Rd E Robinson St Ref St Webste r Trt1 Ref0 Main St Ref1 266 Erie County t ont S Trem Trt2 Ref5 SCALE Trt3 Sweeney St Ref2 Ref Miles Ref4 SORCE: ESRI 2011; Ecology and Environment, Inc. 2014; S Army CORPS of Engineers, 2014 Service Layer Credits: Source: Esri, DigitalGlobe, GeoEye, icubed, Earthstar Geographics, CNES/Airbus DS, SDA, SGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS ser Community 2014 Ecology and Environment, Inc.

10 Table 3. Endothall Acid Concentrations Following a Sept 16 application to the Erie Canal. Ref = samples collected outside of the plot. Trt represents samples collected within the treatment plot. Sites with 3 values represent samples collected along the 2 shorelines and 1 collected in the middle of the canal (the middle value represents the site in the center of the canal. Sites with 1 value represent a sample collected in the center of the canal only. Sample Site 2 Hrs Post 5 Hrs Post 21 Hrs Post 27 Hrs Post Ref 0 ND ND Ref 1 ND, ND, , 216, ND 192 ND TRT , 1620, , 1007, , 67, 87 ND, ND, ND TRT , 953, , 1401, , 456, 388 ND, ND, ND TRT , 2140, , 2218, , 1566, 1644 ND, ND, ND Ref 2 (200 m 1737, 305, , 966, ND Ref 3 (400 m ND, ND, ND 1033, 986, , 775, 1137 ND, 333, 299 Ref 4 (800 m ND, ND, ND 523, ND, Ref 5 (1600 m ND, ND, ND ND, ND, ND 273, 226, , 249, 319 Ref Nd Ref Nd 1 Reference sites 8, 9, and 10 were ND at 21 and 27 hrs post treatment Future Efforts: This summary of year1 results will serve as a guide for upcoming discussions regarding control strategies for hydrilla in the Erie Canal. The extensive monitoring efforts provided information that will be instrumental to future planning efforts. The synchronicity of the tuber sprouting suggests that contact herbicides may play a role in monoecious hydrilla eradication programs. Moreover, the fact that we did not observe any significant late season tuber sprouting suggests that the timing of the control effort met our project objectives. The overall 90% reduction in the hydrilla tuber bank and 89% reduction in hydrilla frequency of occurrence met our project objectives. As noted in the report, we were unable to achieve the desired level of hydrilla control near the Service Road ramp. While the technical explanation for this result is straightforward (an inability to maintain adequate exposure to endothall, our approach to mitigate this result requires further discussion with the Canal Corporation and Ecology and Environment, Inc., on how best to reduce flows and the optimal length of time required for flow reduction. Likewise, the impact of the treatment on native vegetation was greater than expected given previous experience with endothall and strategies to mitigate impacts to non-target plants will also be discussed. Overall, we learned valuable information during the first year of this demonstration project. One example of the value of being on the canal on a frequent basis follows. Extensive surveys conducted in November 2013 and late September and October 2014 indicated that hydrilla was not producing axillary turions late in the season. While this may seem like an esoteric observation, it has significant implications as it means that hydrilla transport in the canal is relying on shoot fragments vs. turions. Shoot fragments will very likely not survive a winter while turions would be much more likely to survive and begin a new hydrilla colony where they were deposited. In terms of potential changes to our approach, we feel that monitoring in year 2 should at least be equivalent to and preferably increased to ensure that we are documenting the results. On-site endothall analysis is planned again as determining the real-time status of endothall is critical in working with the Canal Corporation to insure proper adjustments to flow conditions. Following review and comment on

11 this document by the working group, we will provide both the working group and technical review committee proposed treatment options for We would like to recognize the following agency personnel who put in some long days and hours collecting the information summarized above. Recognition of Key Sampling Personnel: NY DEC - Jennifer Tait, Eric Mucha, and Nicole Dimond S Fish and Wildlife Service Denise Clay, Heidi Himes, Robert Haltner, and Eric Snyder S Army Corps of Engineers, Buffalo District Andrew Hannes, Jay Miller, and Eric Hannes