The RHS has issued a runner bean warning as a European bug that devastates the fruit of common garden plants has entered the charity's top ten worst pest list for the first time.

The southern green shield bug feeds on the sap of plants such as tomatoes, raspberries and runner beans, causing misshapen fruit to grow.

Although the emerald green creature usually does not thrive in England as it does across the warmer climates of Europe, the heatwave last year caused it to multiply across gardens.

A sap feeder with some preference for vegetables, especially beans, it became established in Britain in the early 2000s and is thought to have been introduced from mainland Europe.

The immature stages, called nymphs, are distinctively black with white or pink markings and the adult is similar to the harmless native green shield bug but does not feature a brown marking at its rear.

It is thought that the bug could continue to pose an issue across gardens through this year and next.

For 23 years, the Royal Horticultural Society has compiled a list of the most devastating pests and diseases to hit UK gardens.

The most prevalent pest this year is the box tree caterpillar, which has spread from London to Northern Ireland and Wales and is now an issue across the country. This caterpillar devastates box plants and threatens historic gardens.