Baseline study for implementing biological control of aquatic weeds in urban wetlands of Resistencia, Chaco, Argentina

BERTUCCI, SABRINA; SABATER, LARA 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)

Urban wetlands are essential because they provide high biodiversity and valuableecosystem services. In the northeast of Argentina (NEA), particularly in Resistencia city,these wetlands have the crucial role of mitigating floods, however weed invasion canstrongly interfere with this ecosystem service. Mechanical removal is currently applied asthe unique management method, but this strategy is expensive, and does not provide a longterm solution. Thus, the application of biological control emerges as an alternative toimprove weed management. The aim of this study was to carry out a baseline study forimplementing biological control, assessing weed invasion as well as biological andphysicochemical parameters related to water quality, comparing two urban wetlands inResistencia City: the Argüello and Francia lakes. Sampling was carried out during June andJuly 2022. We assessed the invasion status of target weeds, the abundance of biocontrolagents and their natural enemies, as well physicochemical and biological parametersinfluencing water quality. Our results showed that the water lettuce, Pistia stratiotes, wasthe most abundant and problematic weed in both urban lakes. Water lettuce plants weremore vigorous and had a higher reproductive rate in Lake Argüello than in Lake Francia.We found two biocontrol agents associated with water lettuce: Neohydronomus affinis andLepidelphax pistiae. Abundance of N. affinis and other weevil species was only 11individuals/m² in Lake Argüello, while in Lake Francia 260 insects per m² were recorded.L. pistiae was only found in Lake Argüello and its abundance reached 42 individuals/m².Abundance of potential natural enemies (Araneae and Braconids) in relation to biocontrolagents tended to be similar in Lake Argüello, whereas in Lake Francia biocontrol agentswere 3.8 times more abundant than their natural enemies. Data from physicochemical andbiological parameters evidenced contrasting conditions of water quality in both lakes,mainly regarding nutrient content. Our preliminary results suggest that augmentativebiological control will require different management strategies and biocontrol insectabundance in both lakes and that in Lake Argüello, these actions should also becomplemented by treatments tending to minimize nutrient inputs in water.