Use of Coniothyrium minitans and other microorganisms for reducing Sclerotinia sclerotiorum Wenting Zeng, Dechun Wang, William Kirk, Jianjun Hao ⇑ Department of Plant Pathology, 62 Plant Biology Building, Michigan State University, East Lansing, Michigan 48824 USA highlights " The efficacy of three biological control agents has been examined on sclerotial survival of Sclerotinia sclerotiorum. " All test agents are effective to colonize and degrade S. sclerotiorum sclerotia, with Coniothyrium minitans being the most effective. " Increasing the application rate of the agents increases the level of sclerotial degradation. " C. minitans isolate W09 had a faster growth rate than the commercial isolate CON/M/91-08. graphical abstract Colonization of Sclerotinia sclerotiorum sclerotia by Coniothyrium minitans strain W09. Pycnidia (black spherical bodies) and conidia of C. minitans oozing out of sclerotial surface (arrows) of Sclerotinia sclero- tiorum under a dissecting microscope (25 Â magnification). article info Article history: Received 20 May 2011 Accepted 1 September 2011 Available online 31 October 2011 Keywords: Sclerotinia sclerotiorum Coniothyrium minitans Trichoderma harzianum Bacillus subtilis Streptomyces lydicus biological control abstract Biological control agents (BCAs) Bacillus subtilis QST 713, Coniothyrium minitans CON/M/91-08, Streptomy- ces lydicus WYEC 108, and Trichoderma harzianum T-22 were evaluated for their efficacy in the reduction of survival of sclerotia and production of apothecia of Sclerotinia sclerotiorum under controlled environ- ments. A growth chamber assay was conducted where 25 sclerotia were buried in pots containing potting soil, and BCAs were drenched into the soil at various concentrations, and five soybean seeds were planted in each pot. The presence and number of S. sclerotiorum apothecia were recorded daily. Sclerotinia sclero- tiorum sclerotia were retrieved six weeks after seeding and viability was assessed on water agar plates. All BCAs were effective in reducing S. sclerotiorum inoculum at various efficacies. In general, efficacy was positively correlated with the rate of application. At the rate of application when the efficacy did not change significantly by increasing the rate, the BCAs had various reductions of apothecia and sclerotia. B. subtilis reduced apothecia and sclerotia by 91.2 and 29.6%, respectively; C. minitans reduced apothecia and sclerotia by 81.2 and 50%, respectively; Streptomyces lydicus reduced apothecia and sclerotia by 100 and 29.6%, respectively; Trichoderma harzianum reduced apothecia and sclerotia by 80.5 and 31.7%, respectively. In addition, the commercial strain of C. minitans CON/M/91-08, and a wild Michigan strain of C. minitans W09 were compared for their growth and sclerotial reduction. W09 had faster growth rate than the commercial strain, indicating potential diversities of biological control strains to be studied. Published by Elsevier Inc. 1049-9644/$ - see front matter Published by Elsevier Inc. doi:10.1016/j.biocontrol.2011.10.009 ⇑ Corresponding author. Fax: +1 517 353 9704. E-mail address: jjhao@msu.edu (J. Hao). Biological Control 60 (2012) 225–232 Contents lists available at SciVerse ScienceDirect Biological Control journal homepage: www.elsevier.com/locate/ybcon