Black Rot
Economic Information
Black rot is a storage rot that occurs in all cranberry-growing regions. The disease is most prevalent in water harvest of fruit and can result in fruit losses of 15-20%
Symptoms
Black rot is caused by three separate species of fungi,
Allantophomopsis cytisporea,
Allantophomopsis lycopodina, and
Strasseria geniculata.
Black rot is readily recognized by the jet black color of infected berries that is apparent within 8 weeks after harvest. The rot is relatively firm and dry, but with time, infected fruit wither and look prune-like. Often, pycnidia (fungal fruiting bodies) are scattered on the surface of the berry.
Disease Cycle
The black rot fungi overwinter on cranberry plant debris in the duff layer. Pycnidia develop throughout the summer and are mature by harvest time. Conidia (fungal spores) are released into the harvest flood and probably infect fruit through wounds. Disease incidence is directly proportional to the length of time that the fruit remain in the floodwater. Conidia remain viable for up to 6 weeks and can infect fruit through wounds during storage. Most black rot will be evident within 8 weeks after harvest.
Control
Where possible, fruit destined for the fresh market should be dry-raked if black rot has been a chronic problem. Minimizing the time that fruit remain in the floodwater and wet during storage reduces the risk of black rot. Taking care to avoid damaging fruit during harvesting and handling should also decrease black rot incidence.
Chemical control has been ineffective in controlling black rot.
Questions or comments? Please contact Dr. Patty McManus.
This page designed and programmed by Brian Leininger.
|
Fruit Pathology
University of Wisconsin - Madison 