Using Fire and Herbicide to Control Lygodium microphyllum and Effects on a Pine Flatwoods Plant Community in South Florida

Abstract

Lygodium microphyllum (Cav.) R. Br. is a non-native invasive fern that has become a serious problem in many habitats in southern Florida. The effectiveness of fire and/or triclopyr ester in killing L. microphyllum, the time and amount of herbicide required for inspections and re-applications, and the effects of these treatments on a southern Florida pine flatwoods community were examined. These treatments were: (1) herbicide application with bimonthly inspection and re-application if necessary, (2) herbicide application with biannual inspection/re-application, (3) prescribed fire to reduce L. microphyllum biomass followed by biannual inspection and herbicide application, and (4) untreated controls. All fire and/or herbicide treatments killed standing L. microphyllum, and the prescribed fire reduced by about one-half the amount of subsequent herbicide, but not the time, required to kill regrowth. No treatment prevented L. microphyllum regrowth, and every treatment had at least one new frond at the end of the three-year study. Fire and/or herbicide treatments did not permanently decrease native species cover, richness, evenness, or diversity (Shannon's H′), and native species cover increased following biannual herbicide and fire/biannual herbicide treatments. Two-month inspection/retreatment intervals were not more effective than six-month intervals. Lygodium microphyllum can return to former amounts of biomass and cover within a few years of burning. Waiting too long to inspect and retreat negates the benefits of using fire to reduce L. microphyllum biomass.