The etiology of recent pepper anthracnose outbreaks in Florida

Within the last 4–6 years, anthracnose has become an increasingly serious disease on un-ripe, immature (green) pepper fruit in Florida. This contrasts with earlier reports of anthracnose as strictly a ripe-rot disease of ripened (usually red) pepper fruit. The species of Colletotrichum associated with anthracnose on both immature and ripe pepper fruit in Florida was identified. Based on reactions with polymerase chain reaction (PCR)-specific primers, 28 of 50 isolates associated with anthracnose lesions from Florida were identified as Colletotrichum acutatum, including 22 of 22 recovered from immature fruit. Six of the C. acutatum isolates were associated with typical lesions on ripe fruit, but only in fields where lesions on immature fruit were also observed. In contrast, all 17 isolates identified by PCR as Colletotrichum gloeosporioides were recovered from lesions found only on ripe fruit from fields where no lesions on immature fruit were initially observed. No isolates were identified as Colletotrichum capsici or Colletotrichum coccodes. Isolates of C. gloeosporioides grew upto twice as fast in vitro as isolates of C. acutatum, suggesting a way to tentatively differentiate pepper isolates without PCR testing. In addition, C. gloeosporioides produced conidia that were longer and wider than those produced by C. acutatum. The name “early anthracnose” is proposed for the disease on immature fruit caused by C. acutatum.