These fungi over-winter on leaf debris, and can be kept under control with good garden hygiene, such as removing all fallen leaves.
There are a few fungicides still available to the amateur garden to control the problem, e.g Bordeaux Mixture and Mancozeb
Apply the fungicide after the removal of dead leaves, and give a further application a fortnight later.
Trees/shrubs susceptible to attacks should be sprayed in spring.
The fungi frequently attacks the leaves of plants lacking in vigour, correct feeding during the growing season can help to alleviate this.