Sclerotinia Carunculoides, the Cause of a Serious Disease of the Mulberry (morus Alba)'

In 1903, Orton described a disease of the mulberry characterized by the " peculiarly enlarged portions of the aggregated fruit/ ' The disease was said to occur in Georgia, Alabama, and Mississippi. Dr. M. B. Waite, Pathologist in Charge, Office of Fruit Disease Investigations, Bureau of Plant Industry, states that specimens of mulberry fruits showing this condition have been received from various southern States by the United States Department of Agriculture a number of times during the past 20 years. Taubenhaus 3 reports the occurrence of this disease in Texas, where it is known under the name of "popcorn'' disease of mulberry. In July, 1920, specimens of diseased mulberry fruits (Morus alba L.) were received from Scranton, S. C. Specimens of this material show the greatly enlarged condition of the ovary (PI. 1, A), and the calyx lobes are small and nonsucculent instead of being fleshy as in the normal fruits. Upon microscopical examination the ovaries are found to be entirely filled with mycelium and all traces ofhost tissue are lost. The hyphae are compact, producing a typical sclerotium, and preventing the formation or further development of drupelets. A layer of sporogenous hyphae completely envelops this sclerotium and produces small hyaline spores in a compact palisade within the ovary wall (PI. 1, B). The spores, presumably microconidia, are often exuded in immense numbers and collect in what resembles a waxy mass on the outside of the ovary wall (PI. 1, C, a). It is interesting to note the occurrence of microconidia on the diseased fruit, as no reference to microconidia of species of Sclerotinia occurring other than on culture media has been found in the literature. This disease undoubtedly is the same as that reported by Orton. The nature of the disease led us to suspect that we had either a species of Sphacelia, or, more probably, the microconidial stage of the genus Sclerotinia. It was thought that infection probably occurred at the blooming period of the host and resulted in the formation of such a sclerotium. Accordingly on March 18, 1921, an inspection was made of the planting in South Carolina from which diseased specimens had been received in 1920. At that time apothecia (PI. 2, A) of a fungus belonging to the genus Sclerotinia were found in large numbers on the ground beneath the infected trees. The apothecia were attached to the infected