ARS/USDA, Beltsville Agricultural Research Center-West, Beltsville, Maryland 20705, USA

Background and objectives
Development of Gliociadium virens (=Trichoderma virens) as a biocontrol product for control of damping-off diseases caused by Pythium ultimum and Rhizoctonia solani was initiated by the Biocontrol of Plant Diseases Laboratory in cooperation with WR Grace & Co. and subsequently with a successor company, Thermo Trilogy Corp. The objective of this work was to develop through cooperation with private industry a reliable product for use by vegetable and ornamental transplant growers to control persistent problems with damping-off of crop plants.

Materials and methods
Certain criteria were established to initiate G. virens product development: (i) the targeted pathogens (P. ultimum and R. solani) were chosen for their short-term, damping-off disease activity and their importance in seedling production; (ii) indigenous microorganisms, including various genera of fungi and bacteria, were chosen for testing; (iii) a single agent was selected rather than a mixture; (iv) a cropping system was used (glasshouse) in which environmental factors such as pH, moisture, and temperature were relatively constant and the growing medium was relatively uniform; and (v) a specialized market niche was targeted of sufficient value and size to interest commercial development. Trials were carried out in USDA, state experiment station and grower glasshouses as replicated controlled experiments and as grower demonstrations.

Results and conclusions
Commercial formulations of G. virens (GL-21) have been marketed as 'GlioGard', an alginate formulation, and more recently as 'SoilGard', a granular formulation. The development of these products evolved through discovery of the biocontrol fungus in a local Beltsville soil, product development, marketing assessment, product formulation, process development, efficacy assays, registration with the US Environmental Protection Agency (EPA), scale up, and test marketing. A niche market concept for this product was used and applications of the biocontrol agent have been mostly in glasshouse operations for production of ornamental and vegetable seedlings for garden and field transplants. Future development of biocontrol fungi will probably be driven by the need for seed, seedling, and mature plant protection of specially crops for high cash value markets. Currently in the USA, there are four agriculturally motivated movements which can use biocontrol for solving disease problems: (i) discontinuance by year 2001 of use of methyl bromide opens several potential uses for biocontrol; (ii) the sustainable agriculture movement can use biocontrol in conjunction with cultural practices for control of crop diseases; (iii) the mandate to convert a large percentage (75%) of US agriculture to integrated pest management (IPM) requires biocontrol technologies to reduce chemical pesticide usage; and (iv) certification of organically grown produce will require the use of non-polluting, natural systems, such as biocontrol, to avoid destructive plant disease losses. The G. virens product is one of a growing list of fungal antagonists, including Ampelomyces, Candida, Coniothyrium, Fusarium, Myrothecium, Phlebia, Pythium and Trichoderma, as well as bacterial antagonists, including Agrobacterium, Bacillus, Burkholderia, Pseudomonas and Streptomyces (see web site for the USDA/ARS/BPDL: http:/www.barc.usda.gov/psi/bpd//bpdl.html). The development of Soilgard required close collaboration and a diversity of skills and expertise of plant pathologists, fermentation engineers, commercial planners and others. Close proximity and the ability of scientists at both facilities to work together were key to the successful development of a product. The importance of these factors cannot be overly emphasized and may be the key to the success of other microbial biotechnology applications.

1. Lumsden RD, Lewis JA, Locke JC, 1993. In Lumsden, RD, Vaughn JL, eds, Pest Management: Biologically Based Technologies. American Chemical Society, Washington, DC, pp. 196-203.
2. Lumsden RD, Waiter JE, Baker CP, 1996. Canadian Journal of Plant Pathology 18, 463-468.