There are eight different species that cause yield loss of sunflowers; however, Alternaria helianthi is the primary causal agent and most widespread. The main hosts are sunflowers (Helianthus annuus); however, it has been proven that safflower (Carthamus tinctorius), noogoora burr (Xanthium pungens), cocklebur (Xanthium strumarium), and Bathurst burr (Xanthium spinosum) can serve as alternative hosts for the pathogen.
