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MO boo 100 u R too Triclopyr far selective whole -bay milfoil management —•— mea O o sr4 A\ f b t � ;1 r � Oay Po9WePtment to ° OW P°SIte-poant l�9 Figure 4. Tnelopyr concentrations measured following treatment of 50 he at 1500 µglL on Gideons Bay in June 2012. The left panel represents sample sites where triclopyr was applied to larger treatment blocks The right panel represents sample sites In the middle of bay outside of the treatment blocks (sites 9. 10, 11, and 12) and sites within a narrow treatment strip along an exposed shoreline (sites 1 and 2). sampling dates, the majority of the EWM detected was still rated as 1 or 2 (Table 3). CLP showed an increase in fre- quency (8 to 39%) from June 2011 to 2012, however, only 3 bites were rated as 3. Note that the 2012 treatment was scaled back approximately 80% from the 2011 application. This reduced treatment had little impact on EWM frequency, qualitative ratings, or biomass from June to August 2012. Native species in Gideom Bay that showed a negative re- sponse to the bay -wide exposure in 2011 were Myrlophyl- lum sibirzcum, E. candensis, and Z dubia (Table 6). High frequency natives such as C. demersum, P. amplifolius, P. zosteriformis, P richardsonii, and V. americana were not impacted by the application. The lack of initial treatment impact on P. zosteriformis in Gideons Bay contrasted with observations from Grays and St. Albans bays, suggesting that reduced bay -wide concentrations resulted in less overall injury to this plant. The number of sample points with native submersed plants in Gideons Bay remained stable through the evaluation period. In addition, native plant frequency in the littoral zone and species richness in Gideons Bay either increased or were stable from 2011 to 2013 Gables 4 and 6). Several sites in the bay near the 10 -foot contour supported dense EWM or an EWM–C. demersum complex. Much of the EWM recovery in this bay occurred in these deep water off -shore areas (Fig. 5). Plant biomass Changes in overall plant biomass within each bay generally trended toward a slight increase in total biomass between the June and August of each year, regardless of whether man- agement was implemented (Fig. 6). In contrast, the percent of the biomass represented by EWM was highly reduced for at least 2 seasons in all 3 bays following triclopyr treat - meats gable 4). Although areduction in Grays Bay total bay biomass was observed in 2012 between the June and August evaluations, note that EWM biomass initially accounted for 64% of the biomass in the bay in June 2012 (Table 4), and loss of EWM accounted for the majority of the reduction in overall biomass. While frequency data suggested recov- ery of EWM in the season following treatment, the biomass data lagged behind frequency and remained low the sea- son following a whole -bay triclopyr application (Table 4). This finding was also reflected in the rake -toss ratings that suggested values of 1 (small fragments) were often domi- nant in lune of the season following a triclopyr application (Table 3) From a stakeholder perspective, the low biomass of EWM and high frequency of ratings given a 1 in the season fol- lowing treatment suggested that 2 years of EWM control was achieved. Plant biomass was lower in June 2013 (native plant frequency data were similar to prior years), suggesting a delayed onset for sprouting and growth following a cool spring in 2013. The biomass data refuted anecdotal claims of decreased native plant abundance in relation to management of EWM with low use rates of taclopyr. Hydroacoustic transects Data collected along hydroacoustic transects surveyed in each bay during the June and August suggested a general trend for increased submersed plant coverage and biovol- ume (height in the water column) between June and August of each year (Table 4). Notable exceptions included Grays Bay in 2012 following the triclopyr treatment and the de- creased biovolume in St. Albans between June and August 2012 in a year where no treatment was implemented. As 317