Background/Question/Methods Herbicide treatments can be an effective management tool for controlling invasive species, but could be problematic where the invasive species intermingles with native vegetation.  This is typical of Japanese climbing fern (Lygodium japonicum), a non-native vine that invades  a variety of forest ecosystems of the southeastern United States.  It first appears as scattered individuals and then forms thick, tangled mats which intertwine around and eventually overtop ground cover, shrubs, and trees.  The objectives of this study were to evaluate the efficacy of chemical control on Japanese climbing fern and to evaluate the impacts of herbicide treatment to non-target, native groundcover.  We tested the effects of glyphosate, imazapyr, and metsulfuron methyl at three rates and in combination in two pine stands in northwest Florida.  We measured percent cover of Japanese climbing fern on 3 x 3 m treatment plots prior to treatment and one and two years after treatment. Species composition and cover of native vegetation was recorded on two 1 x 1 m subplots at the same time periods.  A mixed models design in ANOVA was used to analyze percent cover reduction of Japanese climbing fern as well as change in cover, richness, and diversity, of non-target species.
Results/Conclusions One year after herbicide application, control of Japanese climbing fern ranged from 84-99%, and there was no statistical difference between treatments.  By year two, plots treated with glyphosate alone or in combination resulted in significantly higher control (88-99%) than imazapyr alone (-5 to 18%) and metsulfuron methyl alone (14-45%) where substantial fern regrowth occurred.  Percent cover of total non-target vegetation was reduced by anywhere from 30-80% after one year, but recovered or slightly increased over pre-treatment values on most plots by year two.  Total non-target cover on plots treated with glyphosate alone or combination increased by about 10% over pre-treatment values, which was significantly greater than the 2-9% decrease on plots treated with imazapyr. Increased cover was primarily attributed to other native, disturbance-related species such as Rubus spp. and Vitis Rotundifolia. At two years, average species richness increased by 3-5 species on plots treated with glyphosate or glyphosate in low-rate combinations and by 0-1 species on other treatments; however, there was no significant change in diversity indices by treatment. The slightly greater increases in cover and richness on glyphosate-treated plots may be attributed to the additional space and resources available after more thorough control of the invasive fern.