Field assessment, in Greece and Russia, of the facultative saprophytic fungus, Colletotrichum salsolae, for biological control of Russian thistle (Salsola tragus) Dana Berner a,⇑ , Anastasia L. Lagopodi b , Javid Kashefi c , Zhanna Mukhina d , Tamara Kolomiets e , Lyubov Pankratova e , Domenique Kassanelly f , Craig Cavin a , Emily Smallwood a a USDA-ARS-Foreign Disease-Weed Science Research Unit, 1301 Ditto Avenue, Ft. Detrick, MD 21702-5023, USA b School of Agriculture, Aristotle University of Thessaloniki, GR 54124 Thessaloniki, Greece c USDA-ARS-European Biological Control Laboratory, Tsimiski 43, 7th Floor, GR 54623 Thessaloniki, Greece d All-Russia Research Institute for Biological Means of Plant Protection, p/d 39, 350039 Krasnodar, Russia e All-Russia Research Phytopathology Institute, VNIIF, B. Vazemy, 143050 Moscow Region, Russia f Department of Botany, Kuban State University, Krasnodar, Russia highlights  Three Russian thistle infested fields in Greece were inoculated with C. salsolae.  Disease caused by C. salsolae reached maximum proportions within 35–55 days.  Disease progress was associated with cumulative rainfall but not temperature.  By 2 years after inoculation, Russian thistle was eliminated from two fields.  Disease progressed in the same way on individual Russian thistle plants in Russia. graphical abstract article info Article history: Received 25 February 2014 Accepted 5 June 2014 Available online 12 June 2014 Keywords: Biological control Colletotrichum gloeosporioides Colletotrichum salsolae Russian thistle Salsola tragus Tumbleweed abstract Russian thistle (Salsola tragus, tumbleweed, RT) is a problematic invasive weed in the United States (U.S.) and is a target of biological control efforts. The facultative saprophytic fungus Colletotrichum salsolae (CS) kills RT plants in greenhouse tests and is specific to Salsola spp., which are not native in the U.S. However, the effectiveness of CS in controlling RT has not been previously demonstrated. The objectives of this study were to determine in field tests: (1) disease progress of CS in time; (2) the relationship of disease progress to rainfall and temperature; (3) the effect of CS on RT plant density. Field tests were established in Serres and Kozani, Greece and Taman and Tuzla, Russia with isolates of the pathogen collected in the respective countries. Solid inoculum was prepared by asceptically inoculating sterile mixtures of grain and grain hulls with axenic cultures of CS. Spore suspensions used in Russia were prepared by blending pure sporulating cultures of CS with distilled water and diluting the suspension to 10 6 conidia per ml. Six field plots, each subdivided into 36 subplots, of an RT infested field in Serres, Greece were inoculated on October 23, 2006 by placing about 300 g of solid inoculum in the center of each plot. Four field plots, sim- ilarly subdivided, in each of two fields at Kozani, Greece were inoculated in the same way on October 1, 2010. RT density was counted and recorded in each sub-plot prior to inoculation and in September in each of 2 years following inoculation. Disease incidence and/or severity in each sub-plot were recorded http://dx.doi.org/10.1016/j.biocontrol.2014.06.003 1049-9644/Published by Elsevier Inc. ⇑ Corresponding author. Fax: +1 301 619 2880. E-mail address: dana.berner@ars.usda.gov (D. Berner). Biological Control 76 (2014) 114–123 Contents lists available at ScienceDirect Biological Control journal homepage: www.elsevier.com/locate/ybcon