Angular white to brown blocks of infected tissue mostly along the veins on the lower leaf surface caused by the fungus Plasmopara cercidis.  The eight or more larger brown spots that are less angular and surrounded by a yellow halo are infections of Pseudocercospora vitis the cause of Pseudocercospora leaf blight.

Close-up of the lower surface of a leaf with angular areas of older and younger infections caused by the fungus Plasmopara cercidis.  White sporangiaphores and sporangia can be seen coming from the younger infected tissue.

Close-up of the lower surface of a leaf with angular areas of younger infections caused by the fungus Plasmopara cercidis.  White sporangiaphores and sporangia can be seen coming from the younger infected tissue.

Close-up of one angular area of younger infection caused by the fungus Plasmopara cercidis.  White sporangiaphores and sporangia can be seen coming from the infected tissue.

Characteristic sporangiaphores and sporangia of the fungus Plasmopara cercidis.

Characteristic sporangiaphores and sporangia of the fungus Plasmopara cercidis.