Gardening courses 2024

Aphids on my Echinops

Aphids come in a number of different guises; blackfly, green fly, woolly, orange, yellow, red and brown. Particular plants can be very susceptible to aphid attack, such as marigolds, nasturtiums and broad beans, but most plants can be affected.

Other than looking unsightly, aphids can do a lot of damage to plants:

Reduced vigour: Aphids feed by sucking sap from the plant, which can cause the leaves of the plant to curl, reducing the surface area where photosynthesis can occur. They also excrete a sugary substance called honeydew which encourages the growth of sooty moulds, also reducing the ability of sunlight to reach the plant cells to photosynthesise.

Transmission of viruses: Some aphids also transmit viruses, which can be a problem for many plants, for example Dahlias, tulips, members of the cucumber family, strawberries and many others.

Methods of control

Short term strategies

  • Squish them (kitchen roll makes this a less disgusting task)
  • Carefully hose them of the plant with a jet of water, making sure you don't flatten the plant in your efforts
  • Don't feed susceptible plants with nitrogen-rich fertilisers - it encourages soft leafy growth which the aphids love
  • Spray the pests with insecticidal soap sprays. First check that there are no natural predators amongst the colonies, doing the job for you.

Longer term strategies

  • Attract the natural predators of aphids into your garden, by growing a range of pollen and nectar rich plants, and providing habitats such as bug hotels and water features. Natural predators include ladybirds, lacewings, birds, hoverflies, spiders and parasitic wasps. For more info, see the link below.
  • If the aphids are attacking greenhouse plants, then you can order some of these natural predators on-line (not the birds). Google "biological controls for aphids" for a list of suppliers.

Recognising natural predators

Ladybirds and their larvae munch their way through hundreds of aphids a day

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Lacewings and their larvae also love to lunch on aphids!

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Parasitic wasps are also a useful garden visitor.