It causes Kerria twig and leaf blight, a highly contagious disease native to the United States but until 2014 unknown to Great Britain.

Symptoms include multiple red spots on leaves and lesions on the stems, resulting in defoliation and eventual death.

[5] The structures of this fungal pathogen appear on both sides of the leaves of the plant as small red-brown spots, typically measuring 1-5mm in diameter, with dark purple borders.

A key diagnostic feature of Blumeriella kerriae is the presence of acervuli containing conidiophores and conidia within the lesions and leaf spots.

[7] The morphology of Blumeriella kerriae is an important factor in identifying and managing the disease, as it helps distinguish it from other plant pathogens that may cause similar symptoms.

The lesions mature and develop acervuli containing conidia, which can spread via rain splash, wind, and transfer on contaminated tools.

No fungicides that specifically target Blumeriella kerriae are available yet, but tebuconazole with trifloxystrobin is generally recommended for controlling leaf spots on ornamental plants.