[2] Infections may spread rapidly in urban settings with large groups of young trees or in plant nurseries.

[3] This mildew thrives when there are high humidity conditions during the growing season.

[5] The most visible effects, which include "leaf curling, stunting, and distortion,"[6] appear on vulnerable newly emerged leaves.

[4] This infection only appears on leaves, it has no obvious effect on stems and branches.

[5] Fertilization and pollarding increase the number of young shoots, which are the parts of the trees most vulnerable to infection.