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Aphids - a major garden pestAphids are soft bodied insects which live on the sap of a wide number of plants. You will find them on the underside of leaves, and also clustering around buds and flowers. Aphids are generally greenish but can also be black, orange, or shades of brown. The green aphids typically found on roses are usually called "greenfly", and the fat black aphids often found on broad beans are called "blackfly". Some Aphids have wings to fly in from outside and set up new Aphids colonies at any time. Aphids multiply extremely fast during warm weather by producing live young Aphids which already have the next Aphid generation developing inside them when Aphids are born. Look out for AphidsAphids are a few mm across, so you should be able to see them without a magnifying glass. Look for little pear-shaped bodies with thin spindly legs and pipes called "cornicles" at the bottom of their abdomen. They don't move around very fast because they are usually in the process of feeding. Be ready for aphids from Spring to Autumn, and don't let them build up big colonies before it's too late.
 
Aphid DamageAphids suck the sap out of the leaves and stems of the host plants, weakening them and causing distortion to emerging flowers and leaves. Bad Aphid infestations are very debilitating. The buds don't swell fully, and often the flowers and fruit are small. Because aphids feed directly on the sap they are thought to be responsible for passing on viruses and other pathogens from plant to plant. You won't be able to see any holes or bite marks because aphids feed by jabbing their long sharp mouth parts into the soft parts of the plant and sucking out the juices into their body. Aphids excrete a sticky honeydew which turns black in damp conditions, resulting in sooty mould. This blocks the leaf pores and cuts out light falling on the leaves, apart from being quite unsightly. Controlling AphidsTo keep your aphid populations under control you need a number of weapons in your armoury...
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Some
of the more common species found in greenhouses include the green peach
aphid (Myzus persicae) which vary in colour from pale yellow to green to
pinkish-red and the melon or cotton aphid (Aphis gossypii) and the black bean
aphid (Aphis Fabae). There is also an aphid that specialises in brassicas
called the Mealy cabbage aphid (Brevicoryne
brassicae)
