Predation efficiency of the carnivorous aquatic plant Utricularia australis against Asian tiger mosquito Aedes albopictus larvae: Implications for biological control

The Asian tiger mosquito, Aedes albopictus, one of the world's worst invasive animal species and competent vector of many arboviruses, poses a serious threat to human health. An effective and environmentally friendly control strategy is required to mitigate the negative impacts of this pest. The aquatic carnivorous plants of the Utricularia genus, known as bladderworts, feed on invertebrates using their modified leaves as traps (bladders) and could be considered for biological control. The southern bladderwort, U. australis, was used in a no-choice experiment to test its predation ability against Ae. albopictus larvae. Larvae were divided in two size groups: 1st-2nd and 3rd-4th larval instars. Twenty Ae. albopictus larvae were placed inside 1 l plastic cups with a 30 cm long segment of the plant and left for a 7-day period. Twelve segments of U. australis were used, six for each larval size group, counting the number of bladders of each segment at the beginning of the experiment. The 7-day process was repeated five times for each segment/cup over a two-month period. The number of captured larvae and emerged adults was recorded daily. A total of 84 captured larvae were chosen to measure larval length, percentage of larval body trapped within the bladder, bladder perimeter and bladder area, in order to evaluate the ability of the bladders in capturing larvae, by complete or partial suction of the body, depending on the relative sizes of larvae and bladders. Results indicated that U. australis is an effective predator of Ae. albopictus larvae, with a higher efficiency against the 1st-2nd instar group (72%) compared to the 3rd-4th group (39%). The number of captured larvae depended on the number of bladders on each segment and instar group. The percentage of trapped larval body depended on the relationship between bladder size and larval length. Although the bladders effectively captured small larvae by complete suction of the body, they also killed 3rd-4th instar larvae by trapping a small portion of the body within the lumen. The plant segments continuously captured mosquito larvae, with an efficiency that did not decrease during the 2-month period. The use of U. australis as a biocontrol agent against Ae. albopictus larvae could be favoured by its ecological plasticity, broad distribution, its ability to thrive in small containers and the good overlap of the two species regarding phenology and habitat preferences.

Automated summary

The Asian tiger mosquito is a major threat to human health as an invasive species and competent vector of arboviruses. The bladderworts, aquatic carnivorous plants, could be considered as a biological control method against mosquito larvae.