Compost is a carrier medium for Trichoderma harzianum

Trichoderma spp. are one of the most commercialized fungal biocontrol agents. To improve its applicability, while preserving its effectiveness against diseases, a selection of composts were tested as carrier mediums. The population dynamic of T. harzianum was studied in three composts differing in biological characteristics based on the Nematode Index of Compost Maturity (NICM). The results showed a decline in the T. harzianum population, which became stable after six or eight weeks, irrespective of compost, concentration or sterilization. The bioassay with Rhizoctonia solani on bean showed promising results for disease control after storage of the inoculated composts. Nevertheless, T. harzianum was ineffective against R. solani in one compost with a high NICM value, likely related to its sub-optimal physicochemical characteristics and lower root colonization. Compost is a suitable carrier medium for T. harzianum, but the NICM value is not a good indicator to predict the survival rate nor the disease suppression activity of compost inoculated with T. harzianum.