|WOODS, DALE - California Department Of Food And Agriculture
Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2010
Publication Date: 2/18/2011
Citation: Smith, L., Fisher, A.J., Woods, D.M. 2011. Climatic analysis to determine where to collect and release Puccinia jaceae var. solstitialis for biological control of yellow starthistle. Biocontrol Science and Technology. 21(3):333-351.
Interpretive Summary: The rust pathogen, Puccinia jaceae var. solstitialis, collected in Turkey was released in California for classical biological control of yellow starthistle, which is an invasive alien weed. Efficacy of this rust pathogen appears to be limited by climatic requirements. This study used the computer program, CLIMEX, to determine which climatic factors affect establishment of the rust. The rust requires at least an 8 hour dew period in order to germinate and infect the plant, and it is able to grow at temperatures between 10 and 30°C. The analysis predicts that establishment of the rust is limited to the coastal hill and Sierra foothill regions in California. Therefore, other accessions of the rust which are better adapted to the hot dry summer weather of Central California are needed to control the weed in this region. Technical limitations of the computer program are also discussed.
Technical Abstract: The computer program, CLIMEX, was used to study the hypothesis that the low establishment rate of the yellow starthistle rust is caused by poor adaptedness to climate in California. Use of the Match Climates function failed to correctly predict the potential geographic distribution of the rust because 1) it did not incorporate dew period, which is a critical requirement for infection during spring and summer, and 2) it used climatic data during times of the year when the fungus is dormant, and thus not relevant. A Compare Locations model for the rust based on knowledge of its environmental requirements and geographic distribution in California indicates that the rust is likely to establish well only in the coastal hills and Sierra foothills of California. Areas in California's Central Valley, where yellow starthistle is highly invasive, are not suitable for the fungus because of dry and/or heat stress during the summer. The Match Climates function and Compare Locations model were used to predict the best locations in Eurasia to search for rust accessions that should be better adapted to the climate in central California.