Proceedings of the 2022 Mississippi Water Resources Conference

Year: 2022 Authors: Turnage G., Lazaro-Lobo A., Blassingame B., Robinson O., Calhoun K., Ervin G.N.

Limnobium spongia (frogbit) is a free-floating aquatic plant that can produce extensive floating mats that cause negative ecological, social, and economic impacts, which can have negative effects on aquatic fauna (i.e., dissolved oxygen depletion) and restrict waterbody access, navigation, and recreational usage by humans. Literature describing effective control measures for frogbit is minimal. Control efficacy of high and low doses of seven foliar applied herbicides (2,4-D, florpyrauxifen-benzyl, flumioxazin, glyphosate, imazamox, imazapyr, and triclopyr) were evaluated in a mesocosm setting in the summers of 2018, 2020, and 2021. Both emergent and submersed frogbit biomass were reduced 99 to 100% by imazamox (0.56 and 1.11 kg a.i. ha^-1) and imazapyr (0.42 and 0.84 kg a.i. ha^-1) 8 weeks after treatment (WAT) compared to non-treated reference plants. Triclopyr (6.71 kg a.i. ha^-1) reduced frogbit biomass 92% and flumioxazin (0.42 kg a.i. ha^-1) reduced biomass 87 to 93% compared to reference plants. 2,4-D (2.12 and 4.24 kg a.i. ha^-1), glyphosate (2.83 and 5.67 kg a.i. ha^-1), triclopyr (3.36 kg a.i. ha^-1), florpyrauxifen-benzyl (0.02 and 0.05 kg a.i. ha^-1), and flumioxazin (0.21 kg a.i. ha^-1) did not reduce frogbit biomass 8 WAT compared to reference plants. Future research should consider the efficacy of different herbicide combinations to control frogbit, as well as the role of diluent volume per unit area, especially with imazamox and imazapyr. Field studies also will be useful in determining whether the results observed in this study will translate to management of frogbit in natural settings.