No evidence of non-target use of native or economic grasses and broadleaf plants by Arundo donax biological control agents.
Two Arundo donax biological control agents, Tetramesa romana, the arundo wasp, and Rhizaspidiotus donacis, the arundo scale, have been established in Texas, USA and Morelos, Mexico for ten years. A survey was conducted in these areas to determine if there was any use of non-target plant species, especially where the biological control agents occurred at high densities. We found no non-target use in examinations of over 1500 plant specimens representing 5 native grasses, 6 introduced grasses, 2 crop grasses, and one broadleaf species. The survey included the most closely related plant species Phragmites australis, common reed, which is sympatric with A. donax in riparian habitats, and also specimens of Zizania texana, Texas wild rice, a Federally listed endangered aquatic grass species in Central Texas. The field (realised) host range of T. romana and R. donacis confirms the predicted host range of these species from quarantine host range testing.