Mature cowpea (Vigna unguiculata (L.) Walp.) pods with scattered, irregular black spots, similar in appearance to those found on mature soybean (Glycine max (L.) Merr.) pods infected with Phomopsis longicolla T. W. Hobbs, were observed in three fields in Oktibbeha County, MS, in September 1994. In a delayed harvest sample of pods and seeds from one field, a fungus identified as P. longicolla (1) was isolated from more than 60% of surface-disinfested, excised pod disks and from 42% of surface-disinfested seeds. Average frequencies of isolation from seeds harvested at the normal time from the other two fields were 27 and 9%. When surface-disinfested soybean seeds (cv. Avery) were placed along the margins of P. longicolla colonies on potato dextrose agar, the radicals from most germinating seeds became necrotic and many seeds did not germinate. Koch's postulates were completed by reisolating the fungus from diseased tissue.
Reference: (1) T. W. Hobbs et al. Mycologia 77:535, 1985.
