Mass-planted large bromeliads in an urban landscape increase the risk for mosquitoes of pest and public health concern

Exotic bromeliads (Bromeliaceae) are increasingly used in Australian urban green spaces for their hardiness and aesthetic appeal. However, the water-holding tanks and axils of these plants provide habitat for mosquitoes, raising public health concerns that must be balanced with ecological objectives of urban greening. This study investigated the abundance and species richness of immature and adult mosquitoes associated with bromeliad plantings in Sydney, Australia. Between October 2023 and April 2024, immature mosquitoes were sampled weekly from large bromeliads at 17 locations, and adults were collected with CO2; baited Encephalitic Virus Surveillance traps at six sites of contrasting bromeliad density. Specimens were identified to species level, and associations with climatic variables, bromeliad species, and planting characteristics were analysed using generalised linear mixed models. A total of 2,326 immature mosquitoes (three species) and 6,366 adult mosquitoes (ten species) were collected. Aedes notoscriptus and Culex quinquefasciatus dominated both life stages. Total immature abundance increased by 4% for each additional bromeliad in a patch (IRR 1.04, 95% CI 1.02-1.05), and was highest in Alcantarea imperialis (IRR 1.31, 95% CI 0.97-1.77). Weekly-lagged humidity was positively associated with immature counts (IRR 1.01 per 1% increase, 95% CI 1.00-1.03). Adult abundance was significantly higher at high-density compared to low-density bromeliad sites (IRR 0.37, 95% CI 0.23-0.60). Mass plantings of large, water-holding bromeliads might substantially increase mosquito populations in urban environments, elevating pest and public health risks. This highlights the need for integrated mosquito habitat management in sustainable landscaping design and planning.