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SUMMARY
The pathogen associated with a leafspot disease of several species of Nyssa has been commonly identified as Phyllosticta Nyssae Cooke. This organism appears to be limited in its distribution to the southeastern United States.
Lesions are evident during late summer when punctiform fructifications of the fungus are formed on the lower leaf surface. These fructifications, occurring singly, consist of interspersed spermogonia and perithecial primordia.
The spermogonial stage is identical with Phyllosticta Nyssae. By the following spring, the perithecial primordia will have become transformed into mature perithecia of Mycosphaerella nyssaecola (Cooke). Evidence of the presence of conidia in the developmental cycle of M. nyssaecola is lacking.