Aphids, commonly known as greenfly and blackfly feed on plant sap by inserting their mouthparts into plant tissue. In large numbers, aphids can weaken the plant and cause severe distortion of growth through their feeding. Excess sap is secreted by aphids as honeydew, which encourages the growth of sooty mould. Aphids are also able to transmit many plant viruses. There are many species of aphids of economic importance.In high numbers the aphids can create so much honeydew that it drips from trees. Applying Ladybird larvae such as those in Just Greenfly Killer using ladybird larvae can reduce overall numbers. Other predators suck as Lacewing larvae or Hoverfly Larvae will aslo help mreduce aphid numbers.Some contact sprays with no toxic ingredients like Block Out or Savona will also kill aphids on contact. Good coverage is required and regular applications is needed to keep up with the reproductive ability of Aphids.