Some parasites like aphids, mites, and fungi benefit from the warmer and drier climate that we experience during recent years. The mildew fungus for example has increased recently.
Powdery mildew on maple.
Temporal development of mildew infestation on maple (left) and sycamore (right).
The horse-chestnut leaf miner (Cameraria ohridella) has spread across entire Europe since 1984, when it was first discovered in Macedonia. This parasite that has only few natural enemies (i.a. great tits), feeds on the leaf parenchyma between the upper and lower leaf epidermis leading to the typical white brown blotches. With heavy infestation the leaves become brown and curl up. Such typical leaf damages can be observed throughout the city of Basel.
Simultaneous infestation of leaf miner and blotch fungus on horse chestnut.
Temporal development of horse chestnut leaf miner infestation.