Eco-friendly control of mosquito larvae by Brachytron pratense nymph.

The study reported here revealed the biocontrol efficacy of aquatic nymphs of the dragonfly Brachytron pratense against larvae of the mosquito Anopheles subpictus. It was found that during a 24-hour study period, a nymph of B. pratense would consume (mean value of three observations) 66 fourth-instar An. subpictus larvae released in a water bowl containing 3 liters of pond water. The consumption rate was significantly higher (p < .05) during the lights-on phase of the experiment than during the lights-off phase (t = 2.15). Under field conditions, a significant decrease (p < .05) in larval density in dipper samples was observed 15 days after the introduction of dragonfly nymphs (10 individuals) in concrete tanks. The biocontrol potential of the nymphs under field conditions was also indicated by a significant increase (p < .05) in the density of mosquito larvae 15 days after the removal of nymphs. In the control tanks (where no nymphs were introduced), mean larval-mosquito density did not differ significantly throughout the study period (p > .05).