[3] It causes branch dieback, possibly affecting a large portion of the tree canopy, and if severe it can kill entire plants.

[4] It was originally found on fallen fruit of Malus pumila in Great Britain and published and described by Berk as Sphaeropsis malorum in 1836 .

It is first seen as multiple very small, black pimples or pustules under the fruit skin before they break through the covering.

[7] It has been found on Rocky Mountain juniper (Juniperus scopulorum) in windbreak and ornamental plantings in the US.

The fungus also was pathogenic to and caused canker formation on eastern redcedar (Juniperus virginiana) and Chinese juniper (Juniperus chinensis)[4] Prevention efforts may include careful selection of plants, including resistant cultivars, planting in well-draining loose soils, exposure to light and plant spacing to reduce moisture retention.