Wisteria plant under threat from the Asian parasitic insect [Getty Images]

LONDON - MAY 11: A wisteria plant under threat from the Asian parasitic insect, wisteria scale, is shown in flower on May 11, 2010 in London, England. The sap-sucking pest first appeared in London and the South East but is threatening to spread countrywide putting at risk plants that can be over a 100 years old. Wisteria scale is a dark brown insect capable of killing entire plants and came to this country in imported plants from the far east. (Photo by Credit: Claire R Greenway/Getty Images)

Getty Images News Claire R Greenway