What's eating my nymphaea 'chromatella'?

Nymphaea 'Chromatella' is a vigorous yellow-flowered hardy water lily susceptible to the same aquatic pests as all Nymphaea cultivars. Water lily aphids are the most damaging, blackening pads and buds. Water lily beetles skeletonise leaf surfaces, China mark moth caterpillars cut characteristic holes, and ducks can shred foliage in exposed ponds. Avoid pesticides near water.

Dense dark colonies on pads and flower buds causing yellowing, curling, and flower failure; worst in warm, still summers. Hose off into the water for fish to consume; submerge affected pads for 24 hours; do not use insecticide in or near the pond.

Upper leaf surfaces grazed away leaving brown elongated slots that rot; larvae are dark, slug-like, and feed in groups. Wash larvae off with a hose; submerge leaves briefly to drown pests; remove dead marginal vegetation where adults overwinter.

Round or oval sections cut from pads; caterpillars live inside oval cases made of leaf fragments at the water surface. Remove leaf cases by hand; hose caterpillars into water where fish will feed on them; no chemical treatment recommended.

Pads torn, flowers eaten, and rhizomes disturbed; damage worst in early spring when growth is tender. Use monofilament deterrent lines across the pond surface; place wire mesh cloches over emerging growth in spring.