The defoliating biological control agent, Lygomusotima stria (Lepidoptera: Crambidae), reduces rachis and fiddlehead production in Lygodium microphyllum (Schizaeales: Lygodiaceae)

Old World climbing fern, Lygodium microphyllum (Cav.) R. Br., is one of the worst invasive weeds of natural areas of southern and central Florida, United States. The climbing fern forms thick mats that shade native shrubs and trees. Old World climbing fern invades the southern peninsula of Florida, where cost-effective, sustainable control methods are needed. Here, we report the results of greenhouse studies that examined the performance of Lygomusotima stria Solis & Yen larvae, a potential biological control agent of L. microphyllum. We examined the impact of larval feeding on the target weed when grown at a range of fertilizer and herbivore levels. Furthermore, we applied these treatments to guide post-release mass rearing protocols. The results indicate that larvae had greater survival when fed plants at the highest fertilizer level. Two generations of feeding by L. stria larvae decreased rachis weights at the lowest fertilizer levels and fiddlehead numbers. At higher fertilizer conditions, the plants were able to tolerate L. stria herbivory, resulting in no significant changes in plant tissue allocations. The increased larval survival when fed plants grown at high fertilizer levels will benefit both laboratory and field mass production of agents. By impacting rachises and fiddleheads, these results suggest this insect will impede the ability of L. microphyllum to climb substrates, especially in lower resource conditions.