Introduction

Root rot and damping-off pathogens often cause severe problems both in extensively grown field crops and in protected crops such as vegetables and ornamental plants. New control measures are being sought both for environmental reasons and since the possibilities for chemical control are limited. Among these, biological control (Sewell, 1965) seems promising: it is generally believed that the use of biological control will be beneficial and that risks and unwanted side effects are limited. In this chapter, the use of fungal antagonists as biocontrol agents (BCAs) will be discussed.

Most fungi used for biological control of damping-off and root rot are Hyphomycetes, and among these the genera Penicillium, Trichoderma and Gliocladium have received most attention (Kommedahl and Windels, 1981). Mycoparasitic Pythium spp. (Paulitz and Baker, 1987; Lewis et al, 1989; Hockenhull et at., 1992) and nonpathogenic Fusarium spp. (Alabouvette, 1990; Komada, 1990) and other species are also potential BCAs. Although the potential for using fungal antagonists for biological control is well documented (e.g. Papavizas, 1985), there are as yet only a few examples of their use on a commercial scale. However, BCAs such as non-pathogenic Fusarium oxysporum (Rajnchapel-Messai, 1990), Pythium oligandrum (Vesely, 1989), Gliocladium virens (Lumsden et al 1991; see Lumsden and Walter, Chapter 25) and Trichoderma harzianum (Harman and Tronsmo, 1992) are examples of agents that are expected to be on the market in the near future.

This review will be focused mainly on the use of Trichoderma spp. and Gliocadium spp. for the control of root rot and damping-off caused by soilborne pathogens. Possibilities for using biological control for seed-borne diseases will also be mentioned briefly.