Localized induced defenses limit gall formation by eriophyid mite against invasive Lygodium microphyllum

Authors: David, Aaron; Carmona, Andrea; Wheeler, Gregory; Lake, Ellen

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2021
Publication Date: 6/3/2021
Citation: David, A.S., Carmona Cortes, A., Wheeler, G.S., Lake, E.C. 2021. Localized induced defenses limit gall formation by eriophyid mite against invasive Lygodium microphyllum. Environmental Entomology. 50(4):814:820. https://doi.org/10.1093/ee/nvab049.
DOI: https://doi.org/10.1093/ee/nvab049

Interpretive Summary: A potential barrier to the establishment of weed biological control agents is interference from other management tactics that induce plant defenses. Methods that suppress the weed such as feeding by other biological control agents or mechanical removal are especially disposed to inducing plant defenses and potentially limiting agent establishment. Here, we focused on the invasive weed Old World climbing fern (Lygodium microphyllum) and one of its biological control agents, the leaf galling mite Floracarus perrepae. Using experimental assays, we determined that mite gall formation was reduced following damage to the fern's pinnae (i.e., leaflets) both by artificial damage by cutting and by feeding damage by a second biological control agent, the foliage feeding brown lygodium moth. Application of jasmonic acid, a hormone typically involved in plant defenses, similarly reduced gall formation. However, these effects on the mite from induced plant defenses are likely short-lived, and therefore interference between management tactics is unlikely to affect mite establishment.

Technical Abstract: A potential barrier to the establishment of weed biological control agents is interference from other management tactics that induce plant defenses. Methods that suppress the weed such as feeding by other biological control agents or mechanical removal are especially disposed to inducing plant defenses and potentially limiting agent establishment. Here, we focused on the invasive weed Lygodium microphyllum (Cav.) R. Br. (Lygodiaceae, Old World climbing fern) and one of its biological control agents, the mite Floracarus perrepae Knihinicki and Boczek (Acariformes: Eriophyidae). We experimentally damaged potted plants using mechanical and chemical treatments, and measured the responses of the mite in a shade house. Localized damage to the pinnae (e.g., leaflets) via cutting or larval feeding from a second biological control agent Neomusotima conspurcatalis Warren (Lepidoptera; Crambidae) reduced F. perrepae gall formation, but not within-gall mite density. In contrast, damage to rachises (e.g., stems) did not affect galling, likely because plant defense responses were not systemic. Application of jasmonic acid, a hormone typically involved in plant defenses, similarly reduced gall formation but not within-gall mite density. Taken together, we found that localized damage interfered with gall formation but not within-gall reproduction. These effects on the mite from induced plant defenses are likely short-lived, and therefore interference between management tactics is unlikely to affect F. perrepae establishment.