Microbial Recolonization of Compost After Peak Heating Needed for the Rapid Development of Damping-Off Suppression

Compost Science & Utilization, (2005), Vol. 13, No. 1, 65-71
Steven J. Scheuerell (1) and Walter F. Mahaffee (2)
1. Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon
2. USDA-ARS Horticulture Crops Research Laboratory, Corvallis, Oregon

Compost Science & Utilization, (2005), Vol. 13, No. 1, 65-71
Compost removed from the hot (>55°C) core of yard trimmings compost piles was incubated under sterile conditions to observe if suppression could develop due to cooling, or if inoculation with an exogenous source of microbes is a critical factor. Suppression of damping-off caused by P. ultimum did not develop in the cooled compost over seven days of incubation, but compost inoculated 10% v/v with cured yard trimmings compost became suppressive after incubating three to five days. This indicated that the microbial community surviving thermophilic composting is not sufficient to support damping-off suppression and that recolonization of this material is needed to rapidly and consistently produce Pythium suppressive compost for use in greenhouse propagation of seedlings.