 'Urban' has a moderate resistance to Dutch elm disease; in trials conducted by the Istituto per la Protezione delle Piante, Florence, it suffered 49.5% defoliation and 36.5% dieback when inoculated with spores of the causal fungus, compared with 2.8% and 1.2% resp.for 'Sapporo Autumn Gold'.Foliage was adjudged "resistant" to Black Spot by the Plant Diagnostic Clinic of the University of Missouri .