Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 10, 2006
Publication Date: July 29, 2006
Citation: Widmer, T.L. 2006. Impact of synchytrium solstitiale on yellow starthistle seedlings and mature plants. Phytopathology 96:S122. Technical Abstract: Yellow starthistle (YST), Centaurea solstitialis L., is a noxious weed from Europe that has invaded the western United States. Recently, a new disease of YST called false rust was described from southern France. The causal agent was named Synchytrium solstitiale and produces orange galls on infected leaves causing severe leaf deformation. This fungus is being investigated as a biological control agent. Inoculated YST seedlings from France or California seed sustained 88% and 100% infection, respectively. In the greenhouse, all infected French seedlings survived to the rosette stage, while 33% of the California seedlings died. Compared to non-infected control seedlings, plant dry weight was reduced in the infected California plants but not in the plants from France. To measure impact of this disease in the field, infected and asymptomatic YST rosettes were tagged in 2004 and 2005 in a naturally infected field site in France. After maturity, the mean heights of the infected and asymptomatic plants were 11.5 and 29.3 cm, respectively, in 2004, and 11.5 and 25.7 cm, respectively, in 2005. Both number of flowers and stem diameters were lower in the mature plants that were infected at the rosette stage than the asymptomatic plants in both years.