Water Lily Aphid
Water lily aphids form colonies of greenish-brown on the upper surfaces of water lily leaves and various pond margin plants.
They are also attracted to dead leaves so removing any yellowing or dead leaves from the pond will help keep them away.
Control with pesticides can be quite difficult due to access, meaning prevention is often the best cure.
Knowing the aphid’s life cycle can be an advantage.
The aphids overwinter as eggs on a number of prunus species, e.g. blackthorn, cherries, and plums.
The eggs hatch in spring, and the aphids feed on the new host plants foliage until early summer when winged forms of the aphid develop.
Prudent spraying at this time with a suitable insecticide can help to reduce the numbers transferring to the waterside plants.
Alternatively, gently remove any affected water lilies from the pond or water garden.
Place them in a large bucket, and apply an insecticidal soap solution mixed to the manufacturers instructions.
Leave the lilies in this solution for the period recommended by the manufacturer.
After the recommended period rinse the water lily plants in clean water, then place them back in the pond.
For those aphids that survive and migrate to the waterside, control is limited.
In small ponds, aphids can be wiped off the leaves and flower buds.
In larger ponds, directing a strong jet of water at the plants foliage will dislodge many of the aphids and expose them to predation by fish.
In autumn, the winged aphids migrate back to their winter host plants.