Aphids are one of the main garden pests, damaging crops and flowers
They are small insects which feed on sap and typically cluster around soft young growth and buds and are large enough to be seen with the naked eye. The most common are greenfly, which are often seen on roses. Blackfly, most commonly, cluster around the young growth of broad beans. Symptoms of an infestation include: stunted growth, curled leaves, poor growth rate, mottled leaves, distorted flowers, poor crop yields, wilting and eventually death. They excrete honeydew which attracts sooty mould, this blocks the plants pores and by stopping sunlight reaching the leaves prevents photosynthesis.
Non-chemical control
- Squash them by hand.
- Spray with a garlic solution; a clove of garlic crushed into a pint of tepid water.
- Spray with a solution of washing-up liquid and tepid water; 2 tablespoons in a gallon of water.
- Spray with a strong jet of water to dislodge the aphids. The disadvantage of this method is that it can only be used on robust plants.
- Pyrethrum based non-chemical spray; this should be used on a regular basis.
- Plants which attract aphid’s natural predators should be incorporated into the garden scheme. Natural predators include: ladybirds, hoverfly larvae, lacewing larvae and parasitic wasps.
- Biological control insects can be used in the greenhouse but are not suitable for outdoors.
- Feed the birds; bluetits are especially fond of aphids.
- Blackfly on broad beans can be controlled by pinching out the top few centimetres of the plant when it has set the crop. This soft top is delicious steamed and served with butter.
All the non-chemical methods can take some time to become effective.
Chemical control
Contact insecticides must be sprayed directly onto the aphids so make sure both sides of the leaf and the stem are thoroughly covered. This treatment must be repeated several times.
Systemic insecticides permeate into the sap and are ingested by the aphids so just need spraying onto the leaves. There are several ready to use products in garden centres.
