Effect of herbicide treatments on above- and belowground biomass of Japanese climbing fern

Background/Question/Methods

Lygodium japonicum (Japanese climbing fern) is an exotic plant that has become a major problem throughout the southeastern United States. L. japonicum can grow into dense, tangled masses that overtop trees, smother understory vegetation, and alter fire behavior. Invasions are especially problematic in plantations managed for pine straw as pine straw bales may serve as vectors for L. japonicum dispersal. Due to the economic impacts of invasion, developing effective control techniques is particularly important. In addition to its sprawling fronds aboveground, the fern also forms an extensive root system and spreads via rhizomes. In order to achieve complete eradication, control methods must address belowground growth. Therefore, the purpose of this study was to evaluate the efficacy of herbicides with different modes of action on controlling above- and belowground L. japonicum growth. Pots of two native soils (sandy loam, loamy sand) were planted with L. japonicum before being treated with 12 herbicides at three rates (0.5x, 1x, 2x of recommended rate). Each treatment along with a control was replicated 10 times and organized in a complete randomized block design. Blocks were sampled at one and two months after treatment, and dry biomass was measured for fronds, roots, and rhizomes. 

Results/Conclusions

Preliminary results show that above- and belowground biomass varied among herbicide treatments. Two months after herbicide treatment, glyphosate (Accord XRT II – containing surfactant) at 2x of recommended rate yielded the lowest mean frond biomass for both the sandy loam (15.66 g ± SE 3.22) and loamy sand (16.89 g ± SE 1.68) as well as the lowest mean root biomass for sandy loam (9.80 g ± SE 1.05). A second formulation of glyphosate (Accord concentrate – without surfactant) was also effective and exhibited the lowest mean root biomass in loamy sand (14.12 g ± SE 2.29) and the lowest mean rhizome biomass in sandy loam (1.82 g ± SE 0.21) when used at 1x of recommended rate. Previous research has found glyphosate to have better visible long-term control of the invasive fern compared to other herbicide types, likely due to its improved efficacy at reducing belowground biomass. Additional work will be done to assess the effect of herbicide treatments on frond, root, and rhizome biomass and nutrient partitioning across harvest dates.