SUMMARYThe cause of pitch canker of southern pines isFusarium moniliformevar.subglutinansrather thanF. lateritiumf. sp.pini.Isolates ofFusariumfrom pine trees with symptoms of pitch canker are characterized by abundant production of microconidia on simple phialides and polyphialides which develop in complex, sympodially branching conidiophores. These isolates are pathogenic to slash and loblolly pine seedlings. Optimum temperature for growth in culture is 24 C. Five isolates ofF. moniliformevar.subglutinansfrom pine paired with single ascospore isolates ofGibberella fujikuroivar.subglutinansfrom India formed fertile perithecia. Eight otherFusariumspecies,F. lateritium (G. boccata), F. moniliforme, F. solani (Nectria haematococca), F. tricinctum, F. equiseti, F. semitectum, F. oxysporum, andF. graminearum (G. seae), were also recovered from pine, but these were nonpathogenic or very weakly pathogenic to pine.