Technical Abstract: Old World climbing fern, Lygodium microphyllum is one of the most problematic invasive weeds impacting natural areas in southern and central Florida. Management has proven difficult and expensive, which prompted interest in the development of biological control options. The brown lygodium moth, Neomusotima conspurcatalis was the first biological control agent to establish field populations in Florida. Following its initial field release in 2008, the moth rapidly developed large populations and caterpillars caused substantial defoliation of lygodium that reduced ground cover by about 50 percent. As populations of the moth have fluctuated over recent years, some re-growth of lygodium has occurred, although data from December 2010 showed that ground cover of lygodium along 12 transects in Martin County was still lower than levels present before the agent was released. Neomusotima conspurcatalis is a tropical insect and populations are substantially reduced during Florida’s cool winter season, which affords a period in spring and early summer when lygodium can grow in the absence of caterpillar feeding pressure. Moth populations increase during late spring and by late summer, caterpillars in zones of population outbreak may reach densities of 4000-16000 caterpillars per square meter of foliage, which causes complete defoliation and significant suppression of lygodium. Parasitic wasps were first recovered from field-collected Neomusotima caterpillars in fall 2008 and since that time parasitism rates have fluctuated from near zero to peaks of 20 to 34 percent. Despite these apparently high rates of parasitism, Neomusotima densities in fixed quadrats during fall 2010 averaged 140 caterpillars per square meter with average maximal densities of 2400 larvae per square meter, which was comparable to an average fixed quadrat density of 350 larvae per square meter recorded at the same sites during fall 2008. Results collected to date suggest that the brown lygodium moth is capable of contributing to suppression of Old World climbing fern in south Florida.