Host range, biology, and thermal tolerance of Lygomusotima stria, a potential biological control agent of Old World climbing fern (Lygodium microphyllum) in the USA

• Lygodium microphyllum is an invasive weed of natural areas of Florida, USA. • The potential biocontrol, Lygomusotima stria feeds only on Lygodium species. • Only Florida has high climatic suitability for L. stria. • Release of this agent will assist in controlling this weed. Old World climbing fern, Lygodium microphyllum (Cav.) R. Br., is one of the worst environmental weeds of southern and central Florida. The weed climbs over other plants, forming thick mats that block sunlight to native shrubs and trees. In the introduced range, Old World climbing fern invades much of the southern peninsula of Florida where cost-effective, sustainable control methods are needed. A potential biological control agent, the defoliating moth Lygomusotima stria Solis & Yen, was collected in Thailand and Singapore and examined to determine if it was safe for release. A series of no-choice tests was conducted on neonate and third instars. The results indicated that L. stria could only feed and complete development on three congeners: the target weed; L. microphyllum; another invasive exotic; L. japonicum; and the native L. palmatum. Oviposition tests indicated that adults laid eggs broadly across many taxa but primarily on members of the Lygodium genus. Multigeneration studies indicated that L. stria could sustain a population on L. microphyllum, L. japonicum, and L. palmatum for at least four generations. However, the results of lower lethal temperature studies indicated that the LLT50 for L. stria immatures ranged from −2.8 to 1.6 °C, indicating L. stria will not persist in areas where the more temperate L. palmatum grows. Thus, L. stria has a very narrow host range and we predict it will not pose a threat to L. palmatum as it has a low tolerance for the colder temperatures where this plant grows naturally. The release of L. stria is expected to safely assist in the effort to manage the invasive weed Old World climbing fern.