In 2001, 880 tiny weevils were released to fight Texas’s worst weed

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.By September 2003, giant salvinia covered only about 1% of the water surface at the release sites, while untreated control areas remained completely covered. The experiment offered a striking example of biological control, using one small species to put pressure on another that had spread across large areas.In 2001, researchers turned to a tiny weevil to fight a giant aquatic weedThe salvinia weevil is native to parts of South America, including south-eastern Brazil, where it occurs alongside giant...