Necrotrophic fungi were cultured after isolation from rust (Puccinia poarum) pustules on leaves of Tussilago farfara, collected in the field. Healthy and rusted (P. poarum) leaves of T. farfara were re-inoculated in a greenhouse with these potential secondary invaders and development of necrosis and death of leaves was determined. Alternaria alternata, Fusarium sp., Phoma exigua and Phoma glomerata caused formation of necrotic tissue and (non-systemic) death of leaves, whereas leaves inoculated with Cladosporium herbarum and Epicoccum nigrum were similar to leaves inoculated with sterile water. Greater necrosis developed when aecia rather than pycnia were inoculated and at both stages secondary damage increased with increasing pustule density. Comparison with other host-rust systems and aspects of biological weed control are discussed.