NATIVE RANGE: North America

FIRST FINDING IN SLOVENIA: 2010

PATHWAYS: spores are accidentally transported with sawing equipment. Secondary spreading with wind and insects.

POSSIBLE TO FIND: June – November

DESCRIPTION: The disease can be recognised as white to ash-grey patches of mycelium on leaves. Infected leaves are wrinkled, deformed, stay smaller and fall off prema-turely. Hyphae extend from the mycelium into the leaves, from which they withdraw nutrients. The mycelium sur-face is powdery due to the many conidia with which the fungi disperses. From the middle of summer onwards, tiny black spots develop on the mycelium. These are fruit-ing bodies with overwintering spores.

HOST PLANTS: Only infects the leaves of plane trees (Platanus spp.). Like all powdery mildews, it primarily infects the parts of the canopy which are exposed to the sun and where temperatures are higher.

STATUS: Widespread throughout Europe. In Slovenia found in Ljubljana and Bovec, for other parts of Slovenia we do not have data yet.  

SIMILAR SPECIES: Sycamore lace bug (Corythucha ciliata) can cause leaves to yellow and fall off prematurely. The lace bugs leave a typical black frass. Adult lace bugs can be most easily found on the underside of leaves.

SOURCE: Field Guide to Invasive Alien Species in European Forests