Upper surface of maple leaf with tan blotches having dark-green halos caused by the fungus Aureobasidium apocryptum.

Upper surface of maple leaf with tan blotches having dark-green halos caused by the fungus Aureobasidium apocryptum.

Close-up of upper surface of maple leaf with tan blotches having dark-green halos caused by the fungus Aureobasidium apocryptum.

Close-up of lower surface of maple leaf with tan blotches having dark-green halos caused by the fungus Aureobasidium apocryptum.

Close-up of lower surface of maple leaf showing one tan blotchy area having a dark-green halo caused by the fungus Aureobasidium apocryptum.

Close-up of lower surface of maple leaf showing tan infected tissue caused by the fungus Aureobasidium apocryptum.  Note the lack of any signs of the pathogen.

Lower surface of maple leaf stained to reveal random acervuli of the fungus Aureobasidium apocryptum.

Lower surface of maple leaf stained to reveal a cluster of acervuli of the fungus Aureobasidium apocryptum.

An acervulus with stained conidia of the fungus Aureobasidium apocryptum.

An acervulus with stained conidia of the fungus Aureobasidium apocryptum.

Conidia of the fungus Aureobasidium apocryptum.