There are not many pond plant pests but here are some that may be affecting your waterlilies and shelf pond plants now. For illustrations of these pond plant pests please visit our Tips and Advice page - What is eating my waterlily leaves?
Some large, neat holes you may find in your waterlily leaves could be a sign of infestation by china mark moth and all the affected leaves should be removed.
The caterpillar will cut holes in the leaves and place them on the underside of the leaf to cover the pupa which will develop under the patch of bitten off leaf. Then the pupa can be exposed by lifting off the patch.
Waterlily leaves may also be disfigured by the Greater Pond Snail - (the pointed shelled snail not the circular shelled ramshorn snail). The Greater Pond snail leaves jelly capsules containing snail eggs on the back of a waterlily leaf - imagine how fast the snail population can increase with a number of jelly calsules on a single leaf.
These can be removed from the leaf with a thumbnail to keep the population under control.
Water aphids can infest a waterlily. Aphid damage makes the leaf look twisted and distorted. Hose them off into the water or take off the infected leaves.
Water plants on the pond shelf don't tend to suffer from many pests or diseases but aphids may affect soft and succulent leaves like those of Alisma or Pontederia species. As the plants are in baskets - drown the aphids by dropping the basket so that the leaves are under water for two or three days. Alisma plantago-aquatica can also suffer from brown spots on their leaves at this time of year after flowering.
For more information see Tips and Advice