The fungus Diplocarpon mali (conidial stage: Marssonina coronaria) occurs in Italy since 2003, , in Germany (Hesse und Baden-Württemberg) since 2010and in Austria and Switzerland since 2011. In the meanwhile, the fungus is distributed throughout Germany.
The main host plant is Malus spp., but in the literature, also Chaenomeles is described as a host plant. The fungus may cause severe early defoliation. Thereby the trees are weakened and thus the sprouting and fruit development are reduced in the subsequent year. Up to now, mainly ecologically managed apple plantations and scrab resistant varieties are concerned, presumably because rarely/no fungicides are used. Severe damage is reported from Korea. In the enterprises, damage can be limited by usual fungicides against apple scrab (Venturia inaequalis) and by means of hygienic measures and removal of infested foliage.
The fungus is naturally distributed through conidiospores and ascospores with wind and water. An introduction via nursery stock is possible in the case of remaining leaves. 

In Germany, D. mali already occurs almost everywhere and partly, it is already widely distributed. Furthermore, there are effective pathways that can hardly be influenced by humans. Thus, § 4a of the Plant Inspection Order is no longer applicable and there is no longer the obligation to report or control.