Ecological Interactions and Biological Control

James E Walter and Robert D. Lumsden

The fungus Gliocladium virens Miller, Giddens and Foster is an important biological control agent ( Papavizas 1985). A formulation of a strain of this fungus (strain GL- 21) was recently registered with the U.S. Environmental Protection Agency (EPA) by W. R. Grace and Co. of Connecticut. The formulation and registration were subsequently sold to the Thermo Trilogy Corporation. The formulation was developed in cooperation with the Biocontrol of Plant Diseases Laboratory (BPDL), U.S. Department of Agriculture (USDA) ( Lumsden et al. 1991). It is intended for use against damping-off diseases of vegetable and ornamental seedlings caused by the soil-borne plant pathogens Pythium ultimum and Rhizoctonia solani in glasshouse operations ( Lumsden and Locke 1989). This fungus is one of the first to be registered for biocontrol of plant diseases; it is available in the United States for commercial use in glasshouse applications.

Certain criteria were considered important in early stages of development of biocontrol agents ( Lumsden and Lewis 1989). In developing a screening method for selecting an appropriate microorganism, the following were considered. The screening would involve (1) the use of a relatively uniform, commercially available soilless medium that is used extensively in commercial glasshouses where the disease problem occurs; (2) targeted pathogens that are important in the confines of a glasshouse where use of a biological control agent would be likely to be most successful because of a relatively uniform environment; (3) microorganisms indigenous to the United States because nonindigenous microorganisms might be conceived as more likely problems for the U.S. environment; (4) a single isolate of a biocontrol agent for control of both pathogens in preference to a mixture of isolates; and (5) a high-value crop important in the ornamental production industry to defray the cost of development and registration. On the basis of these factors, consideration of which would make the process for registration and commercialization of an agent for control of plant diseases easier, a screening program was initiated, and more than a hun

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