In this study, we investigated the effect of three substrate types (wheat straw, white rice and grit-bran) on conidia production of the cellulolytic fungus Trichurus spiralis. Besides the number of conidia produced per gram substrate, enzyme activity and spore vigour of the produced inoculum were assessed. Subsequently, conidia produced on the different substrates were inoculated into non-sterile wheat straw to assess the competitive ability of the different inocula during composting. Grit-bran showed significantly higher conidial yields per gram substrate than the other substrates. However, cellulolytic activity of inoculum produced on grit-bran was significantly lower compared to that of the inoculum produced on either rice or wheat straw. Conidia produced on both rice and grit-bran had a germination rate of around 80%, while conidia produced on wheat straw had a significantly lower germination rate of around 50%. Spores produced on wheat straw and grit-bran had larger food reserves than those produced on rice. Microbial activity in non-sterile straw was significantly enhanced with conidia produced on grit-bran but not in straw inoculated with conidia produced on either rice or wheat straw. Our results suggest that inoculum produced on grit-bran was the most effective in enhancing composting of wheat straw. The results of this study indicate that substrate type can affect the quantity and quality of the resulting inoculum. The data obtained suggest that nutrient-rich substrates, such as wheat bran, not only gave high conidial yields, but that the conidia produced had sufficient vigour to effectively colonise non-sterile substrates. (C) 2003 Elsevier Science Inc. All rights reserved.