Location: Pest Management Research Unit
2007 Annual Report
We developed a novel method for assessing the prerelease impact of candidate weed biocontrol agents in their native range. The method, based on recent findings on “plotless density estimators” or “nearest neighbor spatial analysis,” was developed to provide prerelease assessment of agents in their native ranges. In addition, the methods have the additional capability of evaluating agent impact on the target species, post-release. This accomplishment addresses NP 304 (Crop Protection and Quarantine), Component 9, Biological Control of Weeds, Problem Area 9A, Agent discovery and selection and risk assessment
We provided further evidence that insect/plant pathogen synergisms against perennial invasive weeds may be specific to each system. A link was established between the occurrence of root galls and accessory root disease of the perennial weed Lepidium draba and the presence of the fungal plant pathogen Rhizoctonia solani in diseased roots in the plant’s native range. The link was more precisely drawn by the finding that ten of 12 isolates belonged to a single subspecies of R. solani. This accomplishment addresses NP 304 (Crop Protection and Quarantine), Component 7, Weed Biology and Ecology; Problem Area 7B Taxonomy and Systematics, and Problem Area 9D Combining biological control agents.
We established new methods for identifying microbial species that are numerically predominant in weed rhizosphere. Methods to investigate soil aggregate community structure through culture-based methods allow a more complete picture of microbial feedback (accumulation of changes in soil or rhizosphere microbial community composition) derived from weed monocultures and the multitrophic interactions of natural enemies used to control invasive weeds. This knowledge is being integrated into strategies for restoration of native plant communities along with data on fungal community structure and overall microbial community structure assessed with culture-independent methods. This accomplishment addresses NP 304 (Crop Protection and Quarantine), Component 7, Weed Biology and Ecology; Problem Area 7F Population dynamics.
We identified and characterized differences in patterns of rhizosphere community composition of stands of leafy spurge declining in density and increasing in density. We showed that soft-rotting Erwinia species and Agrobacterium species were more frequently found to be predominant in the rhizospheres plants sampled from declining stands of leafy spurge. Such species, along with other rhizosphere bacteria of varying pathogenicity, could have the possibility of affecting attempts to restore native plant communities. This accomplishment addresses NP 304 (Crop Protection and Quarantine), Component 9 Biological Control of Weeds; Problem Area 9A Agent discovery and selection and risk assessment.
Caesar, A.J. 2006. Uromyces Scutellatus as a keystone species affecting Euphorbia spp. in Europe as shown by effects on density in the field. Biocontrol Science and Technology. 16:1079-1086.
Mladinich, C., Bustos, M., Ustin-Stitt, S., Root, R., Brown, K., Anderson, G.L., Hager, S. 2006. The use of Landsat 7 enhanced thematic mapper plus data for mapping leafy spurge. Rangeland Ecology and Management. 59(5):500-506.
Ustin-Stitt, S., Root, R., Brown, K., Hager, S., Mladinich, C., Anderson, G.L., Dudek, K., Ruiz-Bustos, M., Kokaly, R. 2006. Classification of leafy spurge with earth o;bserving-1 advanced land imager. Rangeland Ecology and Management. 59(5): 507-511.
Gaskin, J.F., Wilson, L.M. 2007. Phylogenetic relationships among native and naturalized hieracium (asteraceae) in Canada and the United States based on plastid DNA sequences. Systematic Botany. 32(2):478-485.
Whitcraft, C.R., Talley, D.M., Crooks, J.A., Boland, J., Gaskin, J.F. 2007. Invasion of tamarisk (Tamarix spp.) in a southern California salt marsh. Biological Invasions. 9(7):875-879.
Gaskin, J.F., Pepper, A., Manhart, J. 2006. Isolation and characterization of ten polymorphic microsatellites in saltcedars (Tamarix chinensis and T. ramosissima). Molecular Ecology Notes. 6(4):1147-1149.
Gaskin, J.F., Kazmer, D.J. 2006. Comparison of ornamental and invasive saltcedar in the USA northern Great Plains using chloroplast and nuclear DNA sequence markers. Wetlands. 26(4):939-950.
Zhang, D., Zhang, Y., Gaskin, J.F., Chen, Z. 2006. Systematics position of Myrtama Ovcz. and Kinz. based on mophological and nr DNA ITS sequence evidence. Chinese Science Bulletin. 51:117-123.
Caesar, T., Caesar, A.J., Gaskin, J.F., Sainju, U.M., Busscher, W.J. 2007. Taxonomic diversity of predominant culturable bacteria associated with microaggregates from two different agroecosystems and their ability to aggregate soil in vitro. Applied Soil Ecology. 36(1):10–21.
Ge, S., Everitt, J.H., Carruthers, R.I., Gong, P., Anderson, G.L. 2006. Hyperspectral characteristics of canopy components and structure for phenological assessment of an invasive weed. Environmental Monitoring and Assessment. 120:109-126