Interactions between Two Biological Control Agents on Lygodium microphyllum

Abstract

Lygodium microphyllum (Lygodiaceae) is an invasive climbing fern in peninsular Florida. Two classical biological control agents are currently being released against L. microphyllum: a leaf galling mite, Floracarus perrepae (Acariformes: Eriophyidae), and a moth, Neomusotima conspurcatalis (Lepidoptera: Crambidae). Little is known about how the two species interact in the field; thus we conducted oviposition choice tests to determine the effects of F. perrepae presence on oviposition behavior in N. conspurcatalis. Further, we conducted feeding trials with N. conspurcatalis larvae to establish the effects of gall presence on larval survival and rate of development, and determine whether N. conspurcatalis larvae would directly consume F. perrepae galls. Neomusotima conspurcatalis laid significantly more eggs on mite galled (52.66 ± 6.211) versus ungalled (34.40 ± 5.587) L. microphyllum foliage. Feeding trials revealed higher mortality in N. conspurcatalis larvae raised on galled (60%) versus ungalled (36%) L. microphyllum material. In gall feeding trials, N. conspurcatalis larvae consumed or damaged 13.52% of galls, and the rate of direct gall feeding increased over time as leaf resources were depleted. Our results suggest that, where N. conspurcatalis and F. perrepae co-occur, competitive interactions could be more frequent than previously anticipated; however, we do not expect these antagonistic interactions to affect the establishment of either agent.