Waterlily Beetle

These dark brown beetles lay clusters of eggs on the surface of waterlily. Shiny black larvae with yellow bellies hatch out after about seven days and feed voraciously on the leaves which gradually  rot away. After summer, the larvae pupate on any foliage above the water level and the hatced beetles overwinter on dead foliage at the waterside. Remove this brown foliage in autumn. In summer, remove damaged leaves and jet the leaves regularly to control the spread. Raise the water level for a day to submerge the waterlily leaves and drown the larvae.