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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGY AND MANAGEMENT OF INVASIVE WEEDS IN THE WESTERN UNITED STATES Title: Monitoring the rust fungus Puccinia jaceae var. solstitialis for biological control of yellow starthistle

Authors
item Fisher, Alison
item Woods, Dale - CALIF. DEPT. FOOD & AG
item Smith, Lincoln
item Bruckart, William

Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Proceedings
Publication Acceptance Date: November 20, 2007
Publication Date: N/A

Interpretive Summary: Yellow starthistle is a noxious weed that infests over 7 million hectares of rangeland in California. In 2003, a rust fungus was released as a classical biological control for yellow starthistle in California. In 2005, a research program was initiated to monitor the life cycle and spread of the fungal pathogen. The fungus was released at two sites representing different climatic zones, the coastal hills and Central Valley, in January 2005 and 2006. Releases resulted in infected plants at both sites in both years. Natural reinfection occurred throughout yellow starthistle's growing season at the Central Valley site but infection did not persist at the coastal hills site. The rust fungus spread at least 100 meters in 2005 at the Central Valley site, but did not spread at the coastal hills site. The results of this study show that the spread of the rust is most concentrated in areas closest to release sites. Dormant spores were produced during plant senescence at both sites in 2005. Our results suggest that the yellow starthistle rust fungus is likely to establish and spread to new yellow starthistle populations in the Central Valley, California.

Technical Abstract: Yellow starthistle (Centaurea solstitialis L.) is a noxious weed that infests over 7 million hectares of rangeland in California. The rust fungus Puccinia jaceae Otth var. solstitialis (P. j. solstitialis) was first released as a classical biological control for yellow starthistle in California in 2003. In 2005, a research program was initiated to monitor the life cycle and spread of P. j. solstitialis. The rust was released at two sites representing different climatic zones, the coastal hills and Central Valley, in January 2005 and 2006. Releases resulted in infected plants at both sites in both years. Natural urediniospore (infective spore) reinfection occurred throughout yellow starthistle's growing season at the Central Valley site but infection did not persist at the coastal hills site. P. j. solstitialis spread at least 100 meters in 2005 at the Central Valley site, but did not spread at the coastal hills site. The results of this study show that the spread of the rust is most concentrated in areas closest to release sites. Teliospores (dormant spores) were produced during plant senescence at both sites in 2005. Our results suggest that P. jaceae is likely to establish and spread to new yellow starthistle populations in the Central Valley, California.

Last Modified: 12/20/2014
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