Ciboria carunculoides, in common with many other members of the genus Ciboria, is a gynicolous species. In some instances only a few of the individual drupelets composing the syncarp may be involved and in others essentially all drupelets are stromatized. The common name, "popcorn disease," is unusually appropriate for this sclerotia disease for the reason that each mature stroma (sclerotium) bears a striking resemblance in size and shape to a grain of popcorn (FIG. 1 ) .Infection occurs at a time when mulberries come into flower. This conclusion was reached as the result of direct microscopic examination by Siegler and Jenkins ( 1923), and is supported indirectly by the fact that in nature the apothecia reach maturity and ascospores are forcibly discharged at this time. The disease is not evident, however, until three or four weeks after anthesis. It may be noted then, that some of the drupelets are larger than the remainder, and that sticky, grayish, columnar extrusions are prominently present at the tips of these affected drupelets (FIG. 3).Soon thereafter the sepals. of healthy fruits are becoming fleshy whereas diseased ones remain firm and corneous. These differences become more marked as the time approaches for normal fruits to ripen. Mature stromatized drupelets are always considerably larger than healthy ones and are always grayish-; i.e., they never assume the color of mature normal drupelets. The forcible expulsion of ascospores and their dissemination by convection currents. is an efficient means of scattering the inoculum( ascospores), as shown by the distribution of diseased fruits throughout the trees. During each of the three seasons covered by these studies all the mulberries borne on the row of trees under observation were severely attacked. These trees are approximately 30 feet tall. Fruits borne on the lowermost branches were neither more nor less abundantly parasitized than those borne on the topmost branches. The abscission of diseased fruits occurs in late June and early July; i.e., at the same time that the healthy ripe fruits are being shed from disease-free trees growing a few blocks away.

- Whetzel, Herbert Hice, and Frederick A. Wolf.: (1945) The cup fungus, Ciboria carunculoides, pathogenic on mulberry fruits^©