Gummy stem blight on melon
Dark pycnidia (asexual stage= Phoma cucurbitacearum) or pseudothecia (sexual stage= Didymella bryoniae) form on the surface of stems, especially for melon and cucumber.
Following laboratory infection of a melon stem, pycnidia (left) and pseudothecia (right) develop on the same tissue piece. Note the size difference in the two fungal structures.Photos courtesy of T.A. Zitter, Cornell University, Ithaca, NY
Closeup of pycnidia (asexual stage= Phoma cucurbitacearum) with prominent ostiole through which conidia are released.
Individual pycnidium surrounded by exuding conidia in the shape of a "spore horn"
Photos courtesy of T.A. Zitter, Cornell University, Ithaca, NY