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Botryosporium longibrachiatum

Botryosporium has an elogate branching main axis.   At intervals along its length, the main axis (or its branches)   produces lateral fertile branches in acropetal (youngest at the tip) succession.   Each lateral branch terminates in a cluster of circa four ampullae (swollen vesicles).   On any cluster of ampullae ALL the conidia are produced synchronously over the surface of the ampullae.   The spores therefore mature sequentially from the base (oldest cluster) to the apex (youngest cluster).    This remarkably microfungus can grow several millimetres tall and is erect at first but falls over with the weight of the elongated heads.   The fngus is nonpigmenetd and colonies are chalk white.

Further Readng:  Plant Dis. 67:1158-1159.  (The American Phytopathological Society, 1983. DOI: 10.1094/PD-67-1158)      In 1982, barn mold of burley tobacco caused by Botryosporium longibrachiatum caused moderate damage at several locations and severe damage at one location in Ontario, Canada. Lesions and sporulation of the fungus occurred first on the midribs and laminae of lower leaves. Eventually, the mold was evident on all leaves. Based on the pattern and extent of mold development, it was concluded that inoculum of B. longibrachiatum was probably present on the crop before harvest. Secondary infection and humid weather contributed to the damage. Botrytis cinerea was present in most curing barns but sporulation was confined to leaf midribs and plant stems.