Harry A. J. Hoitink, Professor, Department of Plant Pathology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio; Carol A. Musselman and Terry L. Moore, Research Assistants, Department of Plant Pathology, Ohio Agricultural Research and Development Center, The Ohio State University; Leona E. Horst, Research Assistant; Charles R. Krause, Adjunct Associate Professor, U.S. Department of Agriculture, Agricultural Research Service, Application Technology Research Unit, Wooster, Ohio; Randy A. Zondag, Ohio State University Extension, Chair and Extension Agent, Lake County, Painesville, Ohio; and Hannah Mathers, Assistant Professor, The Ohio State University, Department of Horticulture and Crop Science, Columbus, Ohio.
Environmental problems caused by application of raw manures and biosolids have made composting an increasingly attractive process to municipalities and more recently also to farmers. Because costs associated with composting typically are higher, composts of high quality must be produced consistently so that they can be distributed into value-added markets.
The peat substitute aspect of composted manures and biosolids used in potting mixes is the most value-added property of composts. Biological suppression of root rots provided by composts has resulted in reduced pesticide use, and this is the second most value-added benefit associated with compost utilization. Composted biosolids and manures release essential micronutrients that can serve as excellent substitutes for mineral additives. This represents the third most valuable property of composted manures and biosolids.
It has been recognized for centuries that composts may suppress root rots. It was established recently, however, that composts may also suppress foliar diseases of plants (1, 4). Unfortunately, a survey of 80 different types of composted products performed from 1997 to 2001 revealed that only one of these composts naturally induced systemic resistance to foliar diseases even though all 80 compost-amended media suppressed Pythium root rot. Thus, suppression of foliar diseases with composts is a rare phenomenon with considerable unreliability for growers.
However, several different biocontrol agents were isolated from this rare batch of compost that induced resistance in plants. Trichoderma hamatum 382 (T382) was identified as the most active inducer of resistance. For that reason, it was included in demonstration trials with composted manures and biosolids on several different ornamental crops. In this report the authors present data from demonstration trials performed in Ohio nurseries in 2002.