Bio-efficacy potential of seaweed Gracilaria firma with copepod,Megacyclops formosanus for the control larvae of dengue vector Aedes aegypti

Mosquitoes are the most critical group of insects in the context of public health, because they transmit numerous diseases, causing millions of deaths annually. The frequent use of systemic insecticides to manage insect pests leads to the destabilization of ecosystems and enhanced resistance to insecticides by pests, suggesting a clear need for alternatives. Marine organisms are a rich source of structurally novel and biologically active metabolites, and cyclopoid copepods are prominent predators in many aquatic ecosystems and have been used as biological agents in successful programs to control mosquito larvae. In this study, we determine the effectiveness of the Taiwanese seaweed Gracilaria firma and different solvent extracts combined with the copepod Megacyclops formosanus for controlling Aedes aegypti. A significant larvicidal potential was recorded after seaweed extract treatment against the dengue vector A. aegypti. Larval mortality was observed after 24 h of exposure in laboratory. All extracts exhibited larvicidal effects; however, the highest larval mortality was observed in the methanol extract of G. firma against A. aegypti larvae (LC₅₀ = 0.251%). The methanol extract of G. firma was more effective than the other extracts and is an ideal eco-friendly approach for the control larvae of the dengue vector A. aegypti.