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Response of the aquatic weeds Crested Floating Heart and Watershield to varying herbicide rate at different application periods
Proceedings of the 2020 Mississippi Water Resources Conference
Year: 2020 Authors: Turnage G., Byrd J.
Watershield (Brasenia schreberi) and Crested Floating Heart (CFH; Nymphoides cristata) are two perennial aquatic plant species that are problematic/weedy in the Southeastern US. Watershield is a native species while CFH is an invasive species from Asia. Both species can negatively affect human and ecosystems processes in aquatic habitats. Both are capable of outcompeting and displacing native plant species for resources thereby disrupting ecosystem processes. Limited data exist concerning effective chemical control (herbicides) methods for both species. This project was conducted to 1) determine if a new liquid formulation of flumioxazin was effective at controlling either species at high and low rates and 2) determine if timing of herbicide application (early vs. late season) could enhance control of either species. Both WS and CFH plants were established in mesocosms at MSU and allowed to grow for one month prior to herbicide applications. Herbicide residues were in contact with target plants for 24 hours then herbicide treated water was drained off and mesocosm tanks refilled. At 4 weeks after treatment (WAT), none of the herbicide treatments had reduced aboveground (AG) biomass of watershield during both application trials when compared to reference plants. However, watershield belowground (BG) biomass was reduced by <90% by both granular rates in the early season trial; in the late season trial, the low rate of granular flumioxazin had an increase (573%) in watershield BG biomass while other treatments were not different from the references. Herbicide treatments had no effect on CFH biomass or propagule production (daughter plants) at either time period. However, there was a difference in CFH BG biomass among herbicide treatments (while none were different from the reference) at the early season application. Also, while not different from references there were no CFH propagules produced by either low flumioxazin treatment during the late season trial; lack of statistical significance is likely due to the low number of replicates (3) in each treatment used for this trial. Future work should utilize more replicates and herbicide rates as well as explore longer exposure times.