Perspectives and challenges for implementing biological control in weed management in subtropical wetlands of Argentina

FRANCESCHINI, M.C; BERTUCCI, S.E.; GERVAZONI, P.B; SABATER, L.M; ALBERTINI, S; FORASTIER, M.E; SOSA, ALEJANDRO

Iguazu

Congreso; XVI International Symposium on Biological Control of Weeds; 2023

Urban wetlands of Argentina are particularly relevant because they provide water storageareas during flood events, reducing the area that experience catastrophic impacts. However,due to their morphometry and function, they are particularly vulnerable to the proliferationof aquatic weeds, which negatively impact biodiversity and ecosystem services. Althoughthere are previous experiences in Argentina where classical biological control was appliedin water bodies of temperate and arid regions, there are none in subtropical wetlands. Thiswork aims to assess the most adequate target weeds and the agents better suited for abiocontrol initiative in subtropical urban wetlands. We also analyse the relevance of thestructure and performance of these wetlands a weed biocontrol initiative. Preliminarymonitoring in 12 urban wetlands allowed us to identify three target aquatic weeds showingpotential for management with biological control: Pistia stratiotes, Pontederia crassipes,and Victoria cruziana. Current management of these weeds is restricted to mechanicalmethods, but it is expensive and does not provide a desirable level of control. In terms ofabundance and impact, the most viable biological control agents could be Neohydronomusaffinis and Lepidelphax pistiae on P. stratiotes, and Neochetina bruchi, Neochetinaeichhorniae and Cornops aquaticum in P. crassipes. There is no previous experience inimplementing biological control in V. cruziana, hence new biocontrol candidates should beevaluated. Almost all wetlands have highly variable areas and are fairly shallow (less than4m deep), with a low frequency of frost during the year. They tend to have insectassemblages dominated by herbivores, with few detritivores, high plant productivity, weedinvasion alternating with algal bloom episodes, polymictic circulation pattern of water, andeutrophic conditions. A multidisciplinary approach integrating examination of all thesecharacteristics could improve the implementation of biological control and wetlandrecovery in the subtropics. Our results also suggest that urban wetlands can be interestingsystems to implement and promote weed biological control in Argentina due to their highvisibility and use, their key role in mitigating flooding in the cities and the rising trend inthe urban planning for preserving and managing these systems in a more sustainable way.More taxonomic and ecological studies on biocontrol agents are recommended, integratingaspects related to water quality. The engagement of policymakers, citizens and stakeholdersinterested in preserving wetlands could substantially contribute to implementing effectivebiological control of aquatic weeds in subtropical urban wetlands of Argentina