Old world climbing fern (Lygodium microphyllum) is an invasive weed in south Florida where it threatens many wetland communities in the Everglades ecosystem. L. microphyllum is native to wet areas in the Old World tropics and subtropics from west Africa to eastern and southern Africa, and eastern India through south-east Asia to northern Australia and the Pacific to Tahiti. The fern entered Florida as a commercial ornamental plant and was first documented to have become naturalized in 1965. However its explosive growth and rapid spread are relatively recent and it is now causing concern because of its dominance of native vegetation in many communities.
L. microphyllum is considered to be a good target for biological control. First, it belongs to a taxonomically isolated group, not closely related to native or economic plants in Florida. Second, the plant is not known to be a weed in its native range, apart from an unconfirmed report of weedy tendencies in Malaysia. Third, non-biological control methods are environmentally damaging and too expensive to use on the scale required to control the plant. Our biological control program is currently focused on surveys for natural enemies of Lygodium species in L. microphyllum's native range, including Australia, southeast Asia and west Africa. Preliminary surveys in southeast Asia and Australia have identified promising natural enemies, including pyralid moths and sawflies. Searches for natural enemies of New World tropical Lygodium species will also be made to find Lygodium specialist herbivores that may be employed as "new association" biological control agents for L. microphyllum.