Project Number: 1920-22000-031-03
Project Type: Specific Cooperative Agreement

Start Date: Aug 01, 2003
End Date: Jul 31, 2006

Objective:
The objective of this proposal is to achieve successful establishment of the rust fungus, Puccinia jaceae var. solstitialis, on yellow starthistle (YST) in California and determine its effectiveness on field populations of its host. The specific objectives are: 1) Refine methods for large scale greenhouse propagation of the rust, 2) Determine susceptibility of California collections of yellow starthistle, 3) Field release and establish the rust throughout the impacted area, 4) Determine the natural spread and limitations on spread of the fungus, and 5) Determine impact of the rust in the field and options to increase impact.

Approach:
The following activities will involve technical support, funded by ARS, after the rust fungus has been shipped to California. There the isolate will be deployed and studied in various ways. It will be necessary to use or adapt established protocols to increase of inoculum of P. jaceae at the Meadowview facility in Sacramento, CA. Aspects of plant growth, temperature, dew period, and lighting, all to achieve maximum spore production at that location will be determined, and methods for optimal spore harvest and storage will be adapted. To get the rust fungus established in the field, release sites have been selected with large stands of YST, favorable environmental conditions, and ease of access for monitoring. These sites are part of ongoing, long-term studies about insect releases. Field release will involve misting of YST plants, inoculating with urediniospores of P. jaceae, and covering plants with tents from evening to early morning to insure adequate moisture during the infection period. Treated sites will be monitored for the success of inoculations (i.e., is there infection on YST?), spread of the pathogen on YST (short and long distance, using transects and field surveys), and damage to YST (e.g., percent mortality at all growth stages, effects of disease on plant phenology and development (e.g., bolting time), yield parameters (number of YST flowers and seeds), and YST biomass, height, and cover). Changes in the plant community will be determined by cataloguing species composition and densities of non-target plants at release sites. Fundamental information will be gathered also on susceptibility of different California YST populations from greenhouse and field studies.