A thick green carpet can make a pond or reservoir appear almost solid, but giant salvinia is a floating fern, spreading across the water rather than growing from the bottom. In Texas and Louisiana, the plant had become difficult to manage, forming dense mats that blocked sunlight, reduced oxygen and interfered with waterways. According to the US Department of Agriculture, in 2001, researchers tried something considerably smaller. They released 880 salvinia weevils at four sites in eastern Texas and western Louisiana. Each adult was only about 2mm long, yet the insect was closely adapted to feeding on giant salvinia. The adults attacked growing tips while their larvae fed inside the plant.
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