This "belle époque" lasted until the First World War, when as a consequence of hostilities, notably in Germany whence at least 40 cultivars originated, and of the outbreak at about the same time of the early strain of Dutch elm disease, "Ophiostoma ulmi", the elm began its slide into horticultural decline. The devastation caused by the Second World War, and the demise in 1944 of the huge Späth nursery in Berlin, only accelerated the process. The outbreak of the new, three times more virulent, strain of Dutch elm disease "Ophiostoma novo-ulmi" in the late 1960s brought the tree to its nadir.