Wikipedia
Pecan Scab is the most economically significant disease of pecan trees (Carya illinoinensis) in the southeastern United States. Fusicladium effusum is a fungal plant pathogen that causes pecan scab. Fusicladium effusum causes lesions and tissue death on pecan twigs, petioles, leaves, nuts and shucks beginning in early spring, with multiple cycles of infection repeating until late summer. Wind and rain spread the fungus to a susceptible host. Control of the disease is achieved by fungicide, sanitation and, in some cases, quarantine.
Since its first description in 1882, the pecan scab fungus has been reclassified nine times. Fusicladium caryigenum, Cladosporium effusum and cladosporium caryigenum are other names commonly associate with the fungus. In 2010, Seyran and colleagues used sequencing of the mitochondrial cytochrome b gene to conclusively classify the pecan scab fungus as Fusicladium effusum.