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

FRANCESCHINI, CELESTE; BERTUCCI, SABRINA; GERVAZONI, PAULA; SABATER, LARA; ALBERTINI, SILVIA; FORASTIER, MARINA; SOSA, ALEJANDRO

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

areas during flood events, reducing the area that experience catastrophic impacts. However, due to their morphometry and function, they are particularly vulnerable to the proliferation of aquatic weeds, which negatively impact biodiversity and ecosystem services. Although there are previous experiences in Argentina where classical biological control was applied in water bodies of temperate and arid regions, there are none in subtropical wetlands. This work aims to assess the most adequate target weeds and the agents better suited for a biocontrol initiative in subtropical urban wetlands. We also analyse the relevance of the structure and performance of these wetlands a weed biocontrol initiative. Preliminary monitoring in 12 urban wetlands allowed us to identify three target aquatic weeds showing potential for management with biological control: Pistia stratiotes, Pontederia crassipes, and Victoria cruziana. Current management of these weeds is restricted to mechanical methods, but it is expensive and does not provide a desirable level of control. In terms of abundance and impact, the most viable biological control agents could be Neohydronomus affinis and Lepidelphax pistiae on P. stratiotes, and Neochetina bruchi, Neochetina eichhorniae and Cornops aquaticum in P. crassipes. There is no previous experience in implementing biological control in V. cruziana, hence new biocontrol candidates should be evaluated. Almost all wetlands have highly variable areas and are fairly shallow (less than 4m deep), with a low frequency of frost during the year. They tend to have insect assemblages dominated by herbivores, with few detritivores, high plant productivity, weed invasion alternating with algal bloom episodes, polymictic circulation pattern of water, and eutrophic conditions. A multidisciplinary approach integrating examination of all these characteristics could improve the implementation of biological control and wetland recovery in the subtropics. Our results also suggest that urban wetlands can be interesting systems to implement and promote weed biological control in Argentina due to their high visibility and use, their key role in mitigating flooding in the cities and the rising trend in the urban planning for preserving and managing these systems in a more sustainable way. More taxonomic and ecological studies on biocontrol agents are recommended, integrating aspects related to water quality. The engagement of policymakers, citizens and stakeholders interested in preserving wetlands could substantially contribute to implementing effective biological control of aquatic weeds in subtropical urban wetlands of Argentina.