Biological control of damping-off on American ginseng (Panax quinquefolius) by Clonostachys rosea f. catenulata (= Gliocladium catenulatum)

Seedling damping-off caused by several soilborne fungal pathogens is a recurring problem for commercial growers of American ginseng (Panax quinquefolius) throughout the major production areas of Canada. The pathogens isolated from diseased seedling roots during 2001 and 2002 included Pythium ultimum and other Pythium species, Phytophthora cactorum, Fusarium solani and other Fusarium species, Rhizoctonia solani, and Cylindrocarpon destructans. Four commercially formulated biocontrol agents - Trichoderma harzianum strain T-22 (RootShield (R) Drench (TM) WP (wettable powder)), Streptomyces griseoviridis strain K61 (Mycostop (R) WP), Trichoderma virens (synonym: Gliocladium virens) strain GL-21 (SoilGard (TM) 12G (granular)), and Clonostachys rosea f. catenulata (synonym: Gliocladium catenulatum) strain J1446 (PreStop (R) WP and PreStop Mix (TM) G (granular)) - were evaluated in commercial gardens of American ginseng at three locations during 2002 and 2003 for efficacy in reducing damping-off. Application of PreStop Mix G as a combination of seed treatment (applied in the fall season) and three soil drenches (applied in the spring season) significantly (P <= 0.05) increased seedling stand; the protection provided by this treatment was comparable to that of a seed treatment with Apron XL (R) LS (solution for seed treatment; active ingredient: metalaxyl-m). Captan (TM) 50 WP, as a seed treatment, showed the highest efficacy in reducing damping-off in this study. The other three biocontrol products did not protect ginseng seedlings against damping-off.