Efforts to establish a foliage-feeding moth, Austromusotima camptozonale, against Lygodium microphyllum in Florida, considered in the light of a retrospective review of establishment success of weed biocontrol agents belonging to different arthropod taxa

Old World climbing fern, Lygodium microphyllum, is a serious invasive weed in south Florida. Development of biological control is vital for sustainable management of L. microphyllum, although the selection of candidate control agents is limited. Austromusotima camptozonale was the first agent to be approved for release against L. microphyllum. From 2004 to 2005, 10,555 adults were released at L. microphyllum-infested sites but subsequent monitoring failed to recover insects. From 2006 to 2007, 30,000 larvae were released, but survivors were never recovered from pine or tree island sites, and were only recovered for three months at cypress sites. Studies in which A. camptozonale eggs and larvae were set out at release sites and subsequently retrieved indicated no evidence of predation or parasitism of eggs, although eggs in pine systems suffered 20% mortality, attributed to high temperatures. No evidence of parasitism of A. camptozonale larvae was detected, although significantly fewer larvae were recovered in treatments to which walking predators had access, relative to Tangle-Trap exclusion treatments. Ants were recovered trapped in Tangle-Trap treatments and had previously being observed preying on A. camptozonale in the field. We conclude that ant predation was a contributing factor in the failure of A. camptozonale to establish. Based on rates of establishment observed in past weed biocontrol programs, use of a lepidopteran agent within the Pyralidae sensu lato would not be a strategy predicted to offer the best likelihood of success. However a herbivore fauna composed predominantly of Lepidoptera offered few alternatives.