Sphagnum peat moss is widely used horticulture and is a common ingredient in potting mixes. It is highly valued as an “organic” growing media component because it provides porosity and holds moisture.
Sphagnum peat moss has several beneficial qualities for crop production in relation to disease incidences and weed problems. Various research reports have confirmed that Sphagnum peat moss has disease suppressive qualities against certain root-rot pathogens. This is due to the presence of beneficial microorganisms. Furthermore Sphagnum peat moss is free from weed seeds; therefore no risk of weed invasions by using this material.
Microorganisms involved in Disease Suppression:
Sphagnum peat moss contain many microorganisms including Bacillus, Arthrobacter, Actinomyces, Streptomyces, Penicillium, Cladosporum, Trichoderma, Mucor, etc (Belanger, 1988 and Tahvonen, 1993). Of these, Trichoderma and Streptomyces are quite effective at suppressing certain root disease organisms due to their synthesis of antibiotics (Tahvonen, 1993). Their presence in Sphagnum moss has been found to suppress root diseases caused by Fusarium, Rhizoctonia solani, Phythium, and Alternaria brassicicola (Tahvonen, 1993 and Chen, 1986). These beneficial microorganisms suppress the above root rot pathogen populations through competition therefore it is difficult for root rot organisms to establish in the Sphagnum peat based growing mixes.
Sources of Sphagnum peat moss vary in microbial populations and composition. Therefore, disease suppression is not always predictable (Tahvonen, 1993). Blonde, fibrous peat from the surface of the bog has higher microbial populations than the darker, decomposed peat from deeper layers in the bog (Hoitink, 1991). Only blonde, fibrous peat, classified as H-2 to H-3 on the von Post decomposition scale (This is the normally harvested partially decomposed peat moss) provides enough beneficial microorganisms to promote disease suppression. Disease suppression lasts about 6-10 weeks (Hoitink, 1997).
Chen, Y. and Y. Avnimelech. 1986. The Role of Organic Matter in Modern Agriculture. Martinus Nijhoff Publishers, Netherlands.
Hoitink, H.A.J., A.G. Stone and D.Y. Han. 1997. Suppression of Plant Diseases by Composts. HortScience 32(2): 184-187.
Tahvonen, R. 1993. The Disease Suppressiveness of Light Colored Sphagnum Peat and Bio-control of Plant Diseases with Streptomyces sp. Acta Horticulturae 342: 37-42. http://www.actahort.org/books/342/342_4.htm
Lakshman Ranasinghe, Ph.D, Agronomist
Theriault & Hachey Peat Moss Ltd