Greenfly – also known as aphids – are pests which can target any garden and in large infestations cause your plants to suffer. Small numbers of greenfly may not cause concern, as they provide food for birds, however many gardeners opt to remove aphids, especially from vegetable patches.
Both greenflies and blackflies can be spotted in almost every garden, and they are actually the sign of a healthy ecosystem at work.
However, too many of them can cause weak growth and even disease in plants according to Gardeners’ World.
Young plants are especially vulnerable to greenfly infestations, and some aphid species carry a range of viruses.
One sign of virus on your plants may be distorted or discoloured foliage – like mottled or streaked leaves.
If your plant is infected with disease, Gardeners’ World advises destroying it, as “viruses aren’t curable”.
Greenfly and blackfly can also cause black mould to develop, due to the honeydew they leave behind. Honeydew is a sticky substance and once infested with mould can “stop leaves photosynthesising and inhibit plant growth.”
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Washing up liquid
If you don’t have the stomach to squash aphids by hand, you can make a solution using just washing up liquid and water.
Thompson Morgan explains: “You can buy insecticidal soaps but many people make up their own using a teaspoon of washing up liquid diluted in three litres of water.
“The aphids are unable to breath under a coating of soap and subsequently suffocate.
“If you intend to try this, then be sure to spray on a dull day as spraying in full sun is likely to scorch the foliage.”
Mix together a teaspoon of washing up liquid into three litres of water and spray the mixture on the infested plants.
How to deter greenfly
Once you’ve battled a greenfly infestation you can take steps to prevent the insects returning.
One method is to plant strong smelling plants like onion, garlic, sage and nasturtium next to plants at risk of infestation to prevent greenfly from invading.
Gardeners’ World also says to limit nitrogen-rich fertiliser to encourage tough leafed plants.
You can also make your garden as bird friendly as possible, to encourage birds to eat the aphids before they become a problem.
