Water Lily Aphid
Water lily aphids form colonies 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.
The simplest way to control these aphids is to keep them from ever becoming a problem, so as soon as you notice them squash them by hand.
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.
Here are a couple of alternatives to using insecticides.:
- Spraying at 10-14 day intervals with a vegetable based oil mixture (see recipe below) will suffocate the aphids but not affect any fish or wildlife in the pond.
Apply the spray in the evening and rinse off the oil the following morning.
Recipe: Mix two parts vegetable oil to eight parts water and a dash of dishwashing detergent.
- 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, although leaving them overnight in the solution is usually quite long enough.
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.