Cypress canker: a pandemic in progress.

Over the past 70 years a destructive blight of Cupressus macrocarpa and other Cupressaceae, caused by Seiridium cardinale, has spread worldwide from California, devastating forests, plantations, and ornamental cypresses. The epidemic has been particularly severe in the Mediterranean region, on C. sempervirens. A similar destructive blight induced by Lepteutypa cupressi, which caused serious losses to Monterey cypresses in East Africa in the 1940s, has now also spread to distant continents, albeit to a lesser extent. There is yet a third wave of canker disease induced by S. unicorne, although this is a milder type. This review deals with problems related to identification of the pathogens, their taxonomy, pathogenesis and role of fungal toxins, and early screening of cypress clones or hybrids for resistance to the pathogens and tolerance to their toxins.