Diaporthe helianthi (stem canker of sunflower).

Abstract No effect of D. helianthi on wild Helianthus spp. in North America has been documented. Though the fungus could be said to have invaded Europe, its spread has probably been mediated by human activity rather than by natural means. In any case, sunflower is an annual exotic crop in Europe, planted in monoculture, and the disease has not affected the extent of sunflower cultivation. So D. helianthi cannot be said to be invasive.