AbstractA formulation containing solubilized Nystatin called Ceratocide, is fungitoxic toCeratocystis ulmi(Buis.) Moreau as shown in laboratory studies.In controlled inoculations studies in eight‐year‐old elm saplings, Ceratocide was shown to have prophylactic utility in Dutch elm disease control when injected 2, 4 or 10 days before a challenge inoculation withC. ulmi. Therapeutic control was not obtained with a single injection of Ceratocide. Most infected trees succumbed to Dutch elm disease either during the same year of treatment or a year la