The arundo wasp, Tetramesa romana, does not control giant river reed, Arundo donax, in Texas, USA

Authors: Showler, Allan; Osbrink, Weste

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2018
Publication Date: 10/25/2018
Citation: Showler, A., Osbrink, W.L. 2018. The arundo wasp, Tetramesa romana, does not control giant river reed, Arundo donax, in Texas, USA. Entomologia Experimentalis et Applicata. 166(11-12):883-893. https://doi.org/10.1111/eea.12732.
DOI: https://doi.org/10.1111/eea.12732

Interpretive Summary: The giant river reed, native to the Mediterranean basin, has become widespread in temperate and subtropical regions worldwide. It is deleterious for clogging waterways and for choking out natural riparian plant communities. In the United States efforts to control the pest have included the release of exotic herbivorous insects. One of them, the arundo wasp, has been reported to utilize primary stalks for oviposition, stunting and killing the plant. In our study, stands of the reed in natural habitats of Kerr County, TX, were sampled monthly for two years and small plots at annual intervals for five consecutive years. Parasitism of primary stalks, regardless of plant age, was rare or nonexistent. Plants that were infested in natural habitats and freshly planted giant river reed grew in dense stands and proliferated regardless of being infested by the wasp. We determined that parasitized lateral shoots can serve as plant propagules by growing roots and shoots as well as nonparasitized controls, hence, the wasp does not impede the ability of the weed to proliferate. The wasp utilizes lateral shoots growing from hardening '1st-year stalks for development in the winter and late spring when the larvae pupate and emerge as adults. We found that appreciable parasitism of a giant river reed only occurs for 8.3% to 16.7% of the plant’s 2-yr lifespan. Adult exit holes remain on the culms during summer. Under field conditions the wasp is a parasite that is well adapted to the reed by not killing or compromising plant development and by not hindering its ability to propagate. Hence, the exotic wasp is ineffective as a biological control agent against giant river reed.

Technical Abstract: Giant river reed, Arundo donax L., native to the Mediterranean basin, has become widespread in temperate and subtropical regions worldwide. It is regarded as being deleterious for clogging waterways and for choking out natural riparian plant communities. In the United States efforts to control the pest have included the release of exotic herbivorous insects. One of them, the arundo wasp, Tetramesa romana Walker, has been reported to utilize primary A. donax stalks for oviposition, stunting and killing the plant. In our study, stands of A. donax in natural habitats of Kerr County, TX, were sampled at monthly intervals for two years and small plots of A. donax at annual intervals for five consecutive years and parasitism of primary stalks, regardless of plant age, was rare or nonexistent. Arundo donax that was infested in natural habitats and freshly planted A. donax grew in dense stands and proliferated regardless of being infested by T. romana. We determined that parasitized culms can serve as plant propagules by growing roots and shoots as well as nonparasitized controls, hence, the wasp does not impede the ability of A. donax to propagate and proliferate. The wasp utilizes A. donax culms growing from hardening '1st-year stalks for development in the winter and late spring when the larvae pupate and emerge as adults. We found that appreciable T. romana parasitism of an A. donax plant only occurs for 8.3% to 16.7% of the plant’s 2-yr lifespan. Adult exit holes remain on the culms during summer. Under field conditions T. romana is a parasite that is well adapted to A. donax by not killing or compromising plant development and by not hindering its ability to propagate. Hence, the exotic wasp is ineffective as a biological control agent against A. donax.