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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

Location: Exotic and Invasive Weeds Research

Title: Monitoring Puccinia jaceae var. solstitialis for Biological Control of Yellow Starthistle (Centaurea solstitialis) in California

Authors
item Fisher, Alison
item Woods, Dale - UNIV. OF WYOMING
item Smith, Lincoln

Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 25, 2007
Publication Date: August 6, 2007
Citation: Fisher, A.J., Woods, D.M., Smith, L. 2007. Monitoring Puccinia jaceae var. solstitialis for Biological Control of Yellow Starthistle (Centaurea solstitialis) in California. Ecological Society of America Abstracts.

Interpretive Summary: Yellow starthistle is an invasive rangeland weed that infests over 14 million acres in California. In 2003 the yellow starthistle rust fungus was released as a classical biological control for yellow starthistle in California. At that time, a monitoring program was initiated to 1) determine the best time to release the fungus, 2) determine if the fungus can complete its full life cycle in California, and 3) determine if the fungus is likely to establish at two field sites. In 2005-2006 the rust fungus was released at a site near Napa, in the coastal hills and near Woodland, in the Central Valley. All releases resulted in infected plants at both sites in both years. Infecting spores were short lived and remained viable less than three weeks in the field. Overwintering spores survived the summer and germinated in the winter, indicating the rust fungus can complete its full cycle in CA. Reemergence, the appearance of the fungus one year after inoculations, occurred only at the Central Valley site. Our results suggest that the yellow starthistle rust fungus is likely to persist in California, although establishment is expected to be limited by local environmental conditions.

Technical Abstract: The rust fungus Puccinia jaceae var. solstitialis (P. jaceae) was first released as a classical biological control for yellow starthistle (YST) in California (CA) in 2003. At that time, a monitoring program was initiated to 1) determine the best time to release the agent, 2) determine if P. jaceae can complete its full life cycle in CA, and 3) determine if the fungus is likely to establish at two field sites. In 2005-2006 P. jaceae was released monthly from January to June at a site near Napa, in the coastal hills and near Woodland, in the Central Valley. All releases resulted in infected plants at both sites in both years. Urediniospores were short lived and remained viable less than three weeks in the field. Teliospores (overwintering spores) emerged as YST senesced and germinated as YST seedlings emerged in the winter. Pycnia were observed shortly after teliospore germination indicating the rust can complete its full cycle in CA. Reemergence, the appearance of the rust one year after inoculations, occurred only at the Central Valley site. Our results suggest that P. jaceae is likely to persist in California, although establishment is expected to be limited by local environmental conditions.

Last Modified: 8/27/2014
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