The results indicate that three groups of fungi, which occupy distinct niches on the plant, can be delimited: biotrophic fungi, colonising green leaf tissue, often without significant visible symptoms (e.g. Didymella and Mycosphaerella); necrotrophic fungi, causing prominent leaf lesions (e.g. Leptosphaeria, Colletotrichum, Myrothecium, Phaeoseptoria and Stagonospora); and fungi associated with and isolated from petioles previously invaded by coevolved insect natural enemies, such as Taosa and Thrypticus spp