Waterlily Pests (beetle, aphid, leaf-mining midges)

Symptoms (Waterlily beetle)
Circular or elongated slots are eaten in the leaves where both adult beetles and larvae can be seen during the summer. The flowers are also damaged by the adult beetles.

Spot them
This pest has two generations during the summer. Adult beetles overwinter in sheltered places and emerge to lay clusters of eggs on the upper surface of lily leaves in May-June. The larvae are up to 9mm long when fully grown and are black with a pale yellow undersurface. They pupate on top of the lily pads. The beetles are yellowish brown and 6-8mm long. The second generation of larvae is present during August to early September.

Symptoms (Waterlily aphid)
Dense colonies of greenish brown aphids form on the upper surface of lily leaves and on the flower buds. White cast aphid skins also litter the leaves. Heavy infestations spoil the appearance of the flowers.

Spot them
Waterlily aphid overwinters as eggs on blackthorn and other Prunus species. The eggs hatch in the spring and the aphids feed on the foliage until early summer when winged forms of the aphid develop. These migrate to waterlilies and other water-side plants where they establish summer colonies. In the autumn there is a return migration of winged aphids to the winter host plants.

Symptoms (Leaf-mining midges)
The leaves gradually decay and are eaten away, especially around the leaf margins.

Spot them
Slender white maggots, up to 6mm long, feed within the leaves at the edges of the damaged areas.