What's eating my sagittaria sagittifolia?

Arrowhead (Sagittaria sagittifolia) is most vulnerable to stem-boring caterpillars (Bellura species) that collapse petioles at the waterline. Ducks and coot graze and uproot plants in shallow ponds. Aphids colonise stems in summer. In the UK, water snails may also graze young emergent leaves.

Larvae bore into hollow petioles downward toward rhizomes, causing stems to wilt and fall over Cut affected stems below water level and dispose of away from the pond. Clear old stems in autumn to reduce overwintering sites.

Tubers and rhizomes dug up and eaten; leaves grazed to stubs at the water surface Plant in aquatic baskets with a gravel cap. Use low pond fencing while establishing in wildlife ponds with high bird pressure.

Yellowing stem tips, sticky honeydew, and sooty mould on flower stalks Strong water jet to dislodge; introduce beneficial insects. Insecticidal soap on foliage only, away from open water.

Holes and ragged edges on young emergent leaves near the waterline Manually remove excess snails if populations are very high; leave moderate numbers as they help control algae.