Project Number: 5325-11220-004-02
Project Type: Specific Cooperative Agreement

Start Date: Sep 19, 2007
End Date: Sep 15, 2012

Objective:
The objective of this cooperative research project is to improve regional management of riparian and upland invasive plant species by integrating biological control agents with other vegetation management strategies. We will characterize the current ecological limits to Lepidium latifolium distribution in western Idaho as a baseline for future evaluation of the effectiveness of biological control, collect comparative pre-release information on perennial pepperweed (PPW) plant traits in its native and exotic ranges and on the associated herbivore arthropod communities, assess the impact of abundant white rust (Albugo sp.) on PPW infestations in the western U.S., assess the identity and impact of abundant stem-mining Ceutorhynchus sp. on PPW infestations in the western U.S., assess PPW dynamics in a range of plant communities identified above using plant demography, develop techniques for restoring infested areas to promote competitive plant communities resistant to reinfestation, complete plant movement modeling research for yellow starthistle to predict movement of plants across actual landscapes, and assess the impact of abundant biocontrol agents for yellow starthistle and potentially adverse interspecific competitive interactions between these biological control agents that could negatively affect the overall biocontrol efficacy.

Approach:
We will use plant occurrence data within a GIS to characterize the current limits to L. latifolium distribution in western Idaho as a baseline for future evaluation of the effectiveness of biological control. Comparative pre-release information on PPW individual plant and plant population traits in its native and exotic ranges and on the associated herbivore arthropod communities will be collected; we are planning to compare individual plant (stem height) and population traits (patch size, % cover, density, biomass) between populations of PPW in its native and exotic range. In addition, we will collect data on the number of associated herbivore species and fungal pathogens and the severity of attack; the latter visually and through plant dissections. The distribution and abundance of abundant white rust (Albugo sp.) on PPW infestations in the western United States will be surveyed, and fungicide exclosure experiments and greenhouse host plant resistance experiments will be used to quantify the effects of white rust on PPW. We will study the distribution, abundance and impact of stem mining weevils and other herbivores attacking PPW in the introduced range with a combination of greenhouse experiments and insecticide exclosure experiments at selected field sites. Permanent plots will be established along transects to follow plant performance that will include ramet production and loss each year and an estimate of seed production from each plot. Identifying plant survival and ramet/genet production across a range of plant communities will allow us to obtain detailed information on how PPW functions within a range of plant communities. We will link the demography work to RAMAS GIS which will allow us to scale from the plant community level to a regional level that likely will also be appropriate for biological control. We previously found that 15% foliar cover of perennial grasses resulted in an exponential decline of yellow starthistle cover in grasslands. A study is underway to determine the rate of mulch needed to maintain seedling establishment. We will monitor establishment rates of each seeded species and determine the percentage cover of weedy species and the seeded species. Models are being developed using biological parameters that focus on general indicators of plant community competitive ability and using environmental parameters defining the physiological limits to yellow starthistle distribution. All parameters important to predicting community susceptibility are also used to model long-distance dispersal of yellow starthistle. Research to further establish the role biological control plays in regulating yellow starthistle will be completed. Experimental field plots will be used to test the effects of different management practices including biological control and weeding of yellow starthistle and other exotics on the performance and population biology of C. bakeri and native vegetation cover. Documents SCA with U. of ID.