Killeen (AP) – An invasive underwater weed is spreading in a Central Texas lake popular with anglers, tangling boat propellers and threatening the fish. The weed is hydrilla, an aquatic plant initially imported and sold as an aquarium plant in the 1950s. It is now recognized as one of the world’s most invasive plants. Fishing guide Bob Maindelle says mats of hydrilla have proliferated in Stillhouse Hollow Lake, making entire coves inaccessible to boats. The Texas Invasive Species Institute says that if left unchecked, hydrilla depletes oxygen, restricts native plant growth and aquatic animals, and hinders water flow.