F.22 Tank with dense Salvinia growth, Sri Lanka

Slide F.22 Tank with dense Salvinia growth, Sri Lanka

The growth of aquatic weeds, such as this tank with dense Salvinia growth in Sri Lanka, presents specific problems in South and South East Asia, where mosquitoes of the genus Mansonia breed. The larvae of these mosquitoes obtain their oxygen from the air roots of aquatic weeds. They transmit brugian filariasis. Weed control is the obvious solution, but may be hard to achieve on a sufficiently large scale once weeds have invaded a reservoir. In smaller reservoirs, community participation secures permanent weed clearing, provided there is an economic benefit (using the weeds as fodder or fertilizer, for example). Biological control methods have also been tested, using insect pests of weeds, or introducing fish or mammals that consume aquatic weeds.