What's eating my nasturtium officinale?

Nasturtium officinale (watercress) is a popular edible water plant. Aphids — especially the watercress aphid — are the main pest. Flea beetles pepper leaves with tiny holes, caterpillars of the large white butterfly can shred foliage, and slugs attack at the waterline. Keep beds flushed with clean water to reduce pest pressure.

Dense colonies under leaves cause yellowing, wilting, and stunted growth; heavy infestations can collapse a bed. Flush beds with fast-flowing clean water daily; introduce ladybirds and hoverflies; remove badly infested stems.

Tiny round shot-holes in leaves reduce yield and make crops unmarketable. Cover beds with fine insect-proof mesh; encourage ground beetles with undisturbed margins.

Larvae eat large ragged holes, sometimes stripping plants entirely in late summer. Check plants daily and hand-pick egg masses and caterpillars; use fine mesh netting as a barrier.

Rasp young shoots at the waterline overnight, leaving slime trails. Set iron-phosphate pellets at the bed margin; hand-pick at dusk; encourage ground beetles.