Cabbage Aphids

The damper, cooler weather is perfect for cabbage aphids. These little creatures will be seen on kale, cabbages, broccoli and other brassicas. You’ll be able to recognise them from their blue/grey colour (they are extremely well camouflaged on brassicas as a result, which means you often won’t spot them until they’ve built up quite a sizeable colony), and from their general persistence. Other aphids might fly away when disturbed (like cabbage greenfly) or get squirted off the plant by a powerful jet of water from the garden hose, but not these little guys! These aphids cling on, and their waxy coating just repels the water.

You’ll find them under leaves or in the corners between leaves and stem. Where they are most of a problem is on young plants as the aphids tend to collect on the growing tip which destroys the plant’s growth. They feed on the plant’s sap and can cause the leaves to be discoloured or distorted (especially on younger plants).

To deal with them, we recommend pruning off any leaves that are hosting a colony and destroying them or putting them on the compost as the aphids can only survive on live plants (but they can survive through winter temperatures, so don’t rely on cold weather to get rid of them from any live plants that you grow this autumn!) Composting the leaves means the aphids will soon have nothing to eat. In really bad instances where the plant’s growing tip has been damage and the plant has been stunted, it’s best to harvest any unaffected leaves before then pulling up the whole plant and composting it.

To prevent them from re-establishing, the most useful thing is to cover your brassicas with an insect proof mesh netting (one without any holes in!) You can also try and encourage ladybirds, beetles and earwigs which all feed on these aphids – this is a good, eco-friendly way of keeping numbers down. There are organic sprays that you can buy from garden centres to control aphids, but we’ve never found them to be hugely effective.