Yellow flag iris invasion in South America: is biological control needed?

GERVAZONI, PAULA B.; SOSA, A.J.; COETZEE, JULIE A.; ORCASBERRO G.; NIN, M. ; FRANCESCHINI M. CELESTE

Puerto Iguazú

Simposio; XVI International Symposium on biological control of weeds, Session Prospects for weed biological control in South America.; 2023

FuEDEI y CERZOS (CONICET), International Organisation for Biological Control (IOBC)

Iris pseudacorus L. is an invasive alien species, introduced from Europe to many othercountries in the world, being classified as highly invasive in many of them. This speciesnot only causes significant ecological damage in natural environments, diminishing nativeflora and structurally modifying ecosystems, but can also invade urban and rural areas,generating large economic losses. Currently, there is an international alliance betweencountries from the native and introduced range aimed at testing the feasibility of applyingclassical biological control against this weed with the candidate Aphthona nonstriata,native to the Old World. Yellow flag iris has been cataloged as invasive with mandatorycontrol in Argentina and Uruguay, and recorded as naturalized in Chile. The first record isfrom 92 years ago in Argentina, and recent studies showed that in this country it is presentthroughout a diversity of habitats, ecoregions, water conditions, and latitudes. Furthermore,studies of potential distribution predict that the invasion can continue to expand in theterritory. In Uruguay, numerous coastal sites are invaded, including protected areas, andthere are currently plans to control and research this plant. Despite the importance of theinvasion, no bio-controllers or other management strategies have yet been assessed. Weassessed the extent of the problem using citizen science, field exploration, literaturereviews, and interviews with park rangers. Citizen science revealed a much higher level ofinvasion than previously recorded in Argentina, indicating the need to apply control.Different methods of mechanical removal and substitution are being applied in protectedand priority areas of Argentina and Uruguay, and although they resulted effective for smallinfestations, they demand periodic effort, and are not feasible for large invasions. Althoughherbivorous species have been detected feeding on the vegetative and reproductive parts ofthe plant, our results suggest an absence of species with biocontrol potential for I.pseudacorus in Argentina. This information emphasizes the need to continue testing thefeasibility of applying classical biocontrol with candidates from the native range of theplant that demonstrate specificity for I. pseudacorus