Host range, biology, and climate suitability of Callopistria exotica, a potential biological control agent of Old World climbing fern (Lygodium microphyllum) in the USA

Abstract

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 Callopistria exotica Guenee, was collected in Hong Kong and examined in quarantine to determine if it was safe for release. Climate modeling analysis was also performed to predict the potential climate suitability of C. exotica in the invaded range. A series of no-choice tests was conducted on 68 plant species from 45 genera, 33 plant families, and 18 orders. The results indicated that C. exotica is highly specific to the target weed, L. microphyllum and a congener that is also an exotic invasive, L. japonicum. The results indicated that the neonates fed and matured to the adult stage on the target weed L. microphyllum (0.71 ± 0.02 proportion survived) and on another invasive fern, L. japonicum (0.84 ± 0.04 proportion survived). No C. exotica neonates survived when fed the non-target species L. oligostachyum. A low proportion survived to the adult stage when fed the non-targets L. palmatum (0.07 ± 0.03), L. venustum (0.01 ± 0.01), and L. volubile (0.07 ± 0.03). Additionally, the few larvae that survived to the adult stage when fed L. palmatum and L. volubile had longer development times (130–150 % longer) and lower pupal weights (70–90 % lower) than those fed the target weed. All neonates perished within 3 days when fed the remaining 62 species evaluated in these no-choice tests. Climate modeling indicated that the suitability of North American climates for the establishment of C. exotica are very high in south Florida but are very unsuitable north of the L. microphyllum invaded range. These results indicated that this potential biological control agent is highly specific to L. microphyllum and L. japonicum and will have no, or very low survival on other non-target species. The release of C. exotica is expected to assist in the effort to manage the invasive weed Old World climbing fern.