Symptoms and Signs
Band canker is unusual because unlike other cankers it extends around the branch or trunk instead of longitudinally along the affected part. Cankers occur on the trunk or the lower portion of scaffold branches, with infection taking place through growth cracks in the bark on young trees. The fungus kills the bark and cambium layer, and the affected area becomes sunken and frequently girdles the limb. During the growing season copious amounts of amber-colored gum exude from the cankered area, forming a necklace or band of gumballs around the affected part of the tree. Although the disease is sporadic, it has started showing more frequently in the last decade. Band cankers are active only during warm spring and summer weather, and usually do not reactivate the following year. Some trees can develop up to three band cankers in the same trunk. Some cankers become chronic, and sometimes scaffolds or entire trees are killed.
Comments on the Disease
Band canker occurs sporadically throughout the Central and Sacramento valleys. It primarily attacks trees in their third to fifth year, although recently even two-year-old trees showed severe band canker symptoms. The tree may fully recover and survive because cankers naturally heal over time. It has most commonly been reported on vigorous Nonpareil trees but can also be found on Padre, Mission, Ne Plus Ultra, Davey, Drake, Carmel, Aldrich, and Price.
Several species in the Botryosphaeriaceae are associated with the disease and the same pathogens can also cause cankers associated with pruning wounds. Other common hosts for these Botryosphaeriaceae include walnut, pistachio, grape, blackberry and numerous other tree species commonly found in riparian areas.
Band canker can become of major importance in young almond orchards. Management practices include
- Remove of other woody hosts of the pathogens, such as abandoned walnut trees and grapevines adjacent to almond orchards (although the host range of these fungi is extensive).
- Avoid trunk injuries.
- Minimize trunk and scaffold wetness from irrigation systems.
- Remove infected branches or trees (without leaving the stumps in the orchard) and wood debris from almond orchards.