WE have all tackled common pests in our gardens such as aphids, slugs, snails and other creatures which can destroy plants if we don't take immediate action.

But, in the last decade, new pests have emerged to attack foliage, flowers and even trees.

Wisteria scale, for example, could wipe out swathes of wisteria, sycamore and even fruit trees, changing the face of local parks, gardens and heritage buildings across the country as well as potentially stunting the billion pound British fruit industry, according to experts at Garden Organic, a leading organic growing charity.

The bug, eulecanium excrescens, a type of scale, was until recently only found in Asia but has come to Britain through the importing of plants.

Left to its own devices, it can take over plants, completely killing infested specimens.

Unlike normal scale, which is flat and brown, this pest grows a grey sack around itself, then lays thousands of eggs underneath it before they hatch and crawl up the plant to feed.

So far, cases have been contained to south London on isolated wisteria plants. But in other parts of the world the creepy-crawly has been known to spread to sycamore and fruit trees.

Sally Smith, head of information at Garden Organic, says: "Thankfully the bugs don't fly so can't spread too quickly on their own, but birds can act as carriers."

Garden Organic advisers recommend several organic techniques to stop the pest spreading. If found, prune out badly-affected areas or spray with a soap based on fatty acids. Smaller parts can be removed by scrubbing with a toothbrush or squashed by hand.

Warmer climates have led to a number of insect pests originating overeas, such as the rosemary leaf beetle, berberis sawfly and the lily beetle, becoming established and spreading in Britain.

The rosemary leaf beetle (chrysolina americana) has shot up the ranks to become one of the UK's most troublesome pests. Originating from southern Europe, it became established in southern England in the mid-1990s. Both the adults and larvae eat the foliage of rosemary, lavender, thyme and sage.

In 2003, the southern green shield bug (Nezara viridula), a sap-sucking insect that feeds on a wide range of plants and is particularly fond of vegetable crops like beans, was found for the first time breeding in the London area.

The lily beetle, Lilioceris lilii, is a voracious pest of lilies and fritillaries, with both the larvae and adult beetles devouring the foliage during spring and summer. It is continuing to spread northwards, although it remains a local problem in Scotland and Wales.