What's eating my grassy arrowhead?

Grassy Arrowhead is largely trouble-free in pond margins. Aquatic leaf beetles (Donacia spp.) and water lily aphids are the main insect threats, grazing on leaves or sucking sap. Waterfowl browse the foliage and tubers. The plant's aquatic habitat limits most land-based pest treatments, so manual removal and encouraging fish is preferred.

Adults scrape the upper leaf surface, leaving pale oval scars; larvae feed on submerged roots and stems; damaged leaves yellow and die back prematurely Remove visibly damaged leaves; encourage fish that eat beetle larvae near pond margins; avoid insecticides in pond water

Black or green clusters on leaves and flower buds; sticky honeydew attracts sooty mould; growth distorted Hose aphids off leaves into the water where fish will eat them; spray overwintering eggs on nearby plum or blackthorn trees in winter with a suitable ovicide

Leaves and tubers browsed at water's edge, especially on young plants; can decimate small plantings quickly Protect young plants with wire cages or netting; plant in deeper water where grazing access is reduced; establish large clumps — mature stands recover well