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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL CONTROL OF INVASIVE PLANTS OF THE NORTHERN GREAT PLAINS
2006 Annual Report


1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter?
Exotic invasive weeds cause about $27 billion annually in economic losses in addition to environmental impacts ranging from displacement of species of conservation concern to altered ecosystem functions. Biologically-based control methods can provide cost-effective, sustainable means of limiting the adverse impacts of invasive plants over extensive rangeland and natural areas. This project focuses on increasing the success of biological control efforts through better scientific understanding of: mechanisms underlying both the impact of agents and patterns of weed and agent dispersal; genetic variation within target weeds and biological control agents; evolutionary relationships of target weeds and agents; synergisms between plant pathogens, deleterious microbes, and arthropod agents; direct and indirect effects of biological control introductions on nontarget organisms; environmental factors affecting weed and biological control agent dynamics and invasion risk; and follow-on effects following suppression of weeds by biological control agents. The project has two specific objectives: Objective 1: Develop and coordinate biological control programs to achieve sustained suppression of Lepidium draba L. (Brassicaceae), Centaurea spp. and Hieracium spp. (Asteraceae), Tamarix spp. (Tamaricaceae), Euphorbia esula L. (Euphorbiaceae), and other invasive plants by: 1a) determining the systematics and phylogeography of target species; 1b) identifying, testing and releasing new arthropods and plant pathogens alone and in synergistic combinations; 1c) assessing rates of establishment, population growth, dispersal and impacts of agents on target weeds, native plants, and associated soil microbial communities. 1d) Integrate biological control agents with chemical, cultural and other control methods to enhance the impact of weed management programs. Objective 2 focuses on identifying key factors and mechanisms affecting the success of biological control programs and plant invasions including: 2a) genetic and phenotypic traits of target weeds that determine the success of invasive plant species in distinct ecological regions; 2b) genetic and phenotypic traits of biological control agents affecting their establishment, population growth, and impact; 2c) the biotic, edaphic, and environmental factors and mechanisms affecting weed establishment and expansion, and success of biological control agents; and 2d) integrate population information from Objectives 1 and 2 with remote sensing imagery and other spatial/temporal databases to develop spatial models of weed invasion risk. Anticipated products of our project include new biological control agents, improved systematic and phylogeographic understanding of target weeds and control agents, improved systems for assessing and monitoring weed and insect populations; elucidation of factors and mechanisms limiting the establishment and success of biological control releases. This will benefit land managers, users of public lands, the general public, and the scientific community in the fields of invasive plant ecology, systematics and biological control. This project will contribute to NP 304 (Crop Protection and Quarantine), component 7 (Weed Biology and Ecology) and component 9 (Biological Control of Weeds). This project will also impact NP 205 (Rangeland, Pasture and Forages), component 1 (Ecosystems and Their Sustainable Management), and component 5 (Integrated Management of Weeds and Other Pests).


2.List by year the currently approved milestones (indicators of research progress)
2005/Year 1 Publish hybridization study of Tamarix ramosissima and Tamarix aphylla. Publish population structure study of Lepidium draba. Molecular systematics of Tamarix-feeding beetles in the genus Diorhabda - Data collection Host specificity testing of Ceutorhynchus assimilis - Data collection Post-release studies on Diorhabda dispersal, population growth, and impact on target and nontarget plants - Data collection Influence of Tamarix genotype on Diorhabda fitness parameters - Data collection Effects of Wolbachia on Aphthona nigriscutis sex ratios - Data collection Field tests of putative aggregation pheromone in A. nigriscutis and A. lacertosa - Data collection Initiate determination of important plant pathogens associated with white top in its native and invaded ranges including Koch’s postulates for these. Identify and survey overseas areas with endemic leafy spurge rust and hawkweed leaf smut. Select sites with new and long-term infestations of salt cedar or white top, and design sampling scheme. Collect soil samples from sites with new and long-term infestations of white top or salt cedar. Isolate and test predominant or typical isolates of microbes on white top or salt cedar from long- or short-term infestations, and assess feedback effects. Select sites with established insect biological control agent populations yet lacking significant impact on stand density. Collect and use aerial hyperspectral imagery data to develop algorithms that reduce positional errors, cross noise and climatic/atmospheric differences in rangeland images to better detect and map weed invasions. Publish preliminary work on the dynamics of biological control agent effectiveness for controlling Tamarix. Initiate identification of remote sensing data needed to temporally evaluate rangeland trends.

2006/Year 2 Publish clonal reproduction study of Lepidium draba. Publish study of Tamarix population structure across North America. Molecular systematics of Tamarix-feeding beetles in the genus Diorhabda - Data collection, analysis and publication Host specificity testing of Ceutorhynchus assimilis - Data collection Post-release studies on Diorhabda dispersal, population growth, and impact on target and nontarget plants - Data collection, analysis and publication Influence of Tamarix genotype on Diorhabda fitness parameters - Data collection, analysis and publication Effects of Wolbachia on Aphthona nigriscutis sex ratios - Analysis and publication Field tests of putative aggregation pheromone in A. nigriscutis and A. lacertosa - Analysis and publication Impact of C. assimilis on Lepidium fitness parameters - Data collection Assess overseas sites for leafy spurge rust and hawkweed leaf smut severity, pervasiveness and impact on stands of target species; collect soil samples and extract inoculum. Extract leafy spurge rust and hawkweed leaf smut inoculum and test for infectivity on respective hosts Initiate tests of resistance of knapweed species from foreign and domestic sources with varying ploidy levels, unique haplotypes or wide geographic origin to Agrobacterium tumefaciens. Collect and use aerial hyperspectral imagery data to refine and validate algorithms that reduce positional errors, cross noise and climatic/atmospheric differences in rangeland images to better detect and map weed invasions. Publish study results on the dynamics of biological control agent effectiveness for controlling Tamarix. Continue identification of remote sensing data needed to temporally evaluate rangeland trends, and collect and format datasets.

2007/Year 3 Publish Lepidium systematics study. Publish hybridization study of whitetop species (Lepidium spp.). Molecular systematics of Tamarix-feeding beetles in the genus Diorhabda - Data collection, analysis and publication Host specificity testing of Ceutorhynchus assimilis - Data collection, analysis and publication Post-release studies on Diorhabda dispersal, population growth, and impact on target and nontarget plants - Data collection, analysis and publication Influence of Tamarix genotype on Diorhabda fitness parameters - Analysis and publication Field tests of putative aggregation pheromone in A. nigriscutis and A. lacertosa - Analysis and publication Impact of C. assimilis on Lepidium fitness parameters - Data collection Complete Koch’s postulates for selected white top pathogens. Test preliminary protocol for leafy spurge rust and hawkweed leaf smut using soil samples from initial sites. Extract leafy spurge rust and hawkweed leaf smut inoculum and test for infectivity on respective hosts Complete of leafy spurge rust and hawkweed leaf smut infectivity tests and prepare publications. Analyze data and prepare publications on enhancing insect-pathogen synergy for weed biological control. Select white top sites to study integrating plant pathogens with reduced herbicide levels. Complete survey for crown gall bacterium in European stands of knapweed species Collect and use aerial hyperspectral imagery data, using sensors capable of multi-state regional coverage, to refine and validate algorithms that reduce positional errors, cross noise and climatic/atmospheric differences in rangeland images to better detect and map weed invasions. Publish study results on the dynamics of biological control agent effectiveness for controlling Tamarix. Begin temporal analysis of datasets to evaluate rangeland conditions, trends and risk to weed invasion. Initiate integration of remote sensing data with ecological models.

2008/Year 4 Publish Centaurea of North America systematics study. Publish Hieracium of North America systematics study. Molecular systematics of Tamarix-feeding beetles in the genus Diorhabda - Analysis and publication Host specificity testing of Ceutorhynchus assimilis - Data collection, analysis and publication Post-release studies on Diorhabda dispersal, population growth, and impact on target and nontarget plants - Data collection, analysis and publication Impact of C. assimilis on Lepidium fitness parameters - Data collection Complete Identification, characterization and comparison of virulence of white top pathogens. Test white top pathogens in combination with other plant pathogens to assess synergistic interactions. Prepare publications on changes in microbial communities due to long-term presence of perennial weeds. Complete analysis of host range data and other phenotypic traits of microbes isolated from long and short-term saltcedar or white top infestations, and correlate with microbial community structure. Complete documentation of impact of supplementary plant pathogen releases at sites with insect biological control agents. Complete assessment of impact of herbicide and plant pathogens on white top stand density or biomass. Analyze results of herbicide and plant pathogen interaction on white top populations. Prepare publication on impact of herbicide and plant pathogen interactions on white top populations. Complete assessment of resistance of various populations of knapweed species to crown gall bacteria (Agrobacteriium tumefaciens) strains in the greenhouse. Assess knapweed populations for their level of catechin production. Complete study on reducing errors in remote sensing data to enhance rangeland management and monitoring, and publish results. Publish study results on the dynamics of biological control agent effectiveness for controlling Tamarix. Continue temporal analysis of regional datasets to evaluate rangeland conditions, trends and risk to weed invasion. Publish preliminary results of rangeland monitoring. Continue integration of remote sensing data with ecological models.

2009/Year 5 Publish study of expansion of Tamarix into Canada. Host specificity testing of Ceutorhynchus assimilis - Data collection, analysis and publication Post-release studies on Diorhabda dispersal, population growth, and impact on target and nontarget plants - Data collection, analysis and publication Impact of C. assimilis on Lepidium fitness parameters - Data collection, analysis and publication Field release experiments using C. assimilis as a biological control agent for Lepidium draba - Data collection Analyze data and prepare publication on knapweed resistance to Agrobacterium. Complete analysis of herbicide and plant pathogen interaction on white top populations and prepare publication on impact of herbicide and plant pathogen interactions on white top populations. Complete tests of white top pathogens in combination with other plant pathogens to assess synergistic interactions. Continue temporal analysis of regional datasets to evaluate rangeland conditions, trends and risk to weed invasion. Publish study results of rangeland monitoring. Begin functional runs of model/remote sensing data combinations to evaluate actual shifts in rangeland condition and identify causal factors.


4a.List the single most significant research accomplishment during FY 2006.
Determined reproductive strategy of a biological control target weed: Hoary cress (Lepidium draba) is a perennial herbaceous weed that has invaded agricultural and natural areas of western North America. Invasions are often composed of dense patches, and it was unclear whether clonal growth via lateral rhizomes or seedling recruitment is the dominant method of patch expansion. To study the clonal structure of this invasive, six patches from three USA populations were analyzed using DNA methods. Results indicated that hoary cress exhibits a strong bias toward patch size increase from clonal reproduction rather than from seedling recruitment. Results indicate that biological control methods that focus on reducing or eliminating seed production would do little to stop expansion of a patch. This accomplishment falls under NP 304 Component 7 Problem Area D: Reproductive Biology and Seed Bank Dynamics.


4b.List other significant research accomplishment(s), if any.
The isolation of a foreign isolate of Agrobacterium tumefaciens from Euphorbia esula for use as a model biogeographic system to study invasive plant ecology. Sites first surveyed in 1992 surveys where symptoms of crown gall on Euphorbia esula were seen were searched in 2004 and 2005 and the causal organisms isolated. Pathogenicity of the isolates were confirmed, thus essentially providing a set of organisms (accompanying previously described domestic isolates of A. tumefaciens from leafy spurge) with optimal features for addressing a major question in invasive species ecology: whether in the process of migrating from Eurasia to North America, invasives would tend to lose resistance to the agents they are “released” from. This accomplishment falls under NP 304 Component 7 Problem Area F: Population Dynamics. The extension of a pattern detection of a complex of soilborne plant pathogens (Fusarium and Rhizoctonia spp. and pythiaceous fungi) occurring in conjunction with root galling and damage caused by the root galling Ceutorhynchus spp. weevils throughout sites surveyed in Europe, from Hungary to France. This finding strengthens the need for including the capacity of this weevil to rapidly stimulate negative feedback, through higher disease occurrence in response to insect root damage, in prerelease studies of potential impact, in line with the emerging consensus that agents should receive such an assessment prior to release. This accomplishment falls under NP 304 Component 9 Problem Area A: Agent Discovery and Selection and Risk Assessment.


4c.List significant activities that support special target populations.
None


4d.Progress report.
None


5.Describe the major accomplishments to date and their predicted or actual impact.
This is the second year of this project and several major accomplishments have already been realized. Diorhabda elongata has been shown to be a complex of 5 well-defined biological species. The genetic analyses we conducted are in strong agreement with collaborators’ studies on morphological variability and reproductive compatibility. Recognition of these cryptic species provides a basis for more informed evaluation and targeting of the specific Eurasian populations of Diorhabda that should be introduced to North America. This accomplishment falls under NP 304 Component 9 Problem Area C: Field Evaluation.

Molecular evidence for a novel hybrid of invasive Tamarix species has also been discovered. DNA markers were developed and used to identify previously undescribed hybrids of two noxious weed species. Hybrids can potentially exhibit traits that are even more invasive than parental species. The result of this research is inclusion of this hybrid in ongoing biological control investigations, and heightened scrutiny and control of populations in natural areas such as National Parks. This accomplishment falls under NP 304 Component 9 Problem Area B: Field Evaluation.

A strong correlation was found between damage caused by root galling weevils (Ceutorhynchus spp.) on white top and the presence of the root-infecting pathogen Rhizoctonia solani. This pathogen is typically undetectable in natural soils. White top plants affected by these insect/plant pathogen interactions are stunted and chlorotic. This is strong evidence that, as has been found with leafy spurge and knapweeds, an efficient insect/plant pathogen synergism may be the key to efficacious biological control. This accomplishment falls under NP 304 Component 9 Problem Area D: Combining Biological Control Agents.

Preliminary tests of differential susceptibility of Russian spotted and diffuse knapweed to the “plant cancer” causing crown gall bacterium has shown wide differences among populations. These populations include unique haplotypes, differing ploidy levels, putative hybrids, and represent wide geographic origins. Reactions ranged from complete mortality to near immunity to crown gall disease. This accomplishment falls under NP 304 Component 9 Problem Area A: Agent Discovery and Selection and Risk Assessment.

Analysis of hyperspectral data in the complex domain accounts for and removes many of the erroneous differences between the images and ground data. Analysis of crop field data collected by yield monitors has resulted in an improvement in predictability from r = 0.368 to r = 0.967. In addition, the data provide insight into sources of error and how the errors can be reduced. While this data was collected over cropland, much of what was developed can be used in increase our understanding of rangeland conditions and trends. This accomplishment falls under NP 304 Component 7 Problem Area C: Early Detection, Rapid Response and Monitoring.


6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
The biological and ecological knowledge generated through this project has been made available to other researchers, to land managers and to the public through brochures, field days, scientific meetings and formal publications. For example, we provided over 100,000 saltcedar leaf beetles to federal, state and private cooperators in Montana and Wyoming to start saltcedar biological control insectaries. We also distributed over 200 brochures entitled “Saltcedar Biological Control Program” to end-users in Montana, Wyoming and Utah, and started 4 new ARS-managed saltcedar biological control research and insectary sites in Montana.

Personnel with the Colorado Dept. of Agriculture visited NPARL to learn and discuss methods for isolating, assessing and utilizing soilborne plant pathogens associated with insect damage to leafy spurge to supplement insect release sites for improved impact. Specialized methods and protocols for sample collection, isolating, identifying, pathogenicity testing, mass culturing and formulating soilborne fungi were explained.


7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Caesar, A.J. Soilborne fungi associated with root galls of Lepidium draba caused by Ceutorhynchus spp. WSSA Annual meeting, NY, NY Feb 12, 2006 (Abstract).

Caesar, A. J. 2006. Rhizosphere bacterial communities associated with insect root herbivory of an invasive plant, Euphorbia esula/virgata. International Society of Microbial Ecology, Vienna Austria, August 18, 2006 (Abstract).

Friedman, J., J. Roelle, J. Gaskin and J. Roth. Inherited Latitudinal Variation in Cold Hardiness in Native Populus and Introduced Tamarix. Evolution 2006, Stony Brook, NY June 2006.

Gaskin, J., D. Kazmer and P. Shafroth. Novel hybrids produced since the introduction of saltcedar and the influence of garden plantings on nearby invasions. Botanical Society of America 2006, Chico, CA August 2006.

Gaskin, J. Hybridization in plant invasions: saltcedar and other examples. 53rd Annual meeting of the Entomological Society of America, Ft. Lauderdale, FL December 2005.

Gaskin, J. Genetic studies applied toward the control of plant invasions: from family to population level. University of Idaho CRISSP Series, Moscow, ID October 2005.

Holtz , B.A., McKenry, M.V., Caesar-TonThat, T.C. and Caesar, A. J. 2005. Wood chipping almond brush to reduce air pollution and to study the effect of wood chips on harvest, soil nutrients, soil aggregation, and the microbial community. Almond Board of California, 33rd Almond Industry Conference Proceedings, pages 225-234. Technical Report.

Holtz, B., Caesar-TonThat, T.C., Caesar, A. and Hoffman, E. 2006. The effect of tillage on decomposing mulch, Verticillium, the microbial community, soil nutrients, and soil aggregation. California Pistachio Industry Annual Report Crop Year 2005-2006, page. 103.

Holtz, B., Caesar-TonThat, T.C., Caesar, A., and Hoffman, E. The effect of tillage on decomposing mulch, Verticillium, the microbial community, soil nutrients, and soil aggregation. California Pistachio Commission 2005 Production Research Reports, Pages 91-95.

Natale, E., S. Zalba and J. Gaskin. Distribution and status of tamarisk (Tamarix spp.) in Argentinean natural environments. XXX Jornadas Argentinas de Botánica. Santa Fe, Argentina November 2005.

Mayer, M., D. Kazmer and J. Gaskin. State of the River. Lower Missouri River Coordinated Resource Management Council. Ft. Peck, MT January 2006.

Mayer, M., D.J. Kazmer and J. Gaskin. Biological control and genetics of saltcedar. Big Horn Drainage Exotic Plant Steering Committee Biological Control Seminar. Riverton, WY. October 2005.

Kazmer, D.J. and M. Mayer. Biological control of saltcedar. Montana Federal Interagency Noxious Weed Working Group. Billings, MT. March 2006.

Mayer, M. and D.J. Kazmer. Biology and biocontrol of saltcedar. Lower Missouri River Coordinated Resource Management Council Annual Meeting. Ft. Peck, MT. January 2006.

Mayer, M. and D.J. Kazmer. Biocontrol of saltcedar. Noxious Weed Management Short Course. Sponsored by Western Society of Weed Science. Chico, MT. April 2006.


Review Publications
Dudley, T.L., Kazmer, D.J. 2005. Field assessment of the risk posed by diorhabda elongata, a biocontrol agent for control of saltcedar (Tamarix spp.), to a non-target plant, frankenia salina. Biological Control. 35:265-275.

Gaskin, J.F., Ryan, F.J., Hrusa, G.F. 2006. Genotype diversity of salsola tragus and potential origins of a previously unidentified invasive salsola from california and arizona. Madrono. 53:246-253.

Gaskin, J.F. 2006. Clonal structure of invasive hoary cress (lepidium draba) infestations. Weed Science. 54(3):428-434.

Gaskin, J.F. and P.E. Berry. 2005. Smilacaceae in Flora of the Venezuelan Guayana, J.A.Steyermark, P.E. Berry, K. Yatskievych and B.K. Holst (eds.). Missouri Botanical Garden Press, St. Louis, USA. P. 184-193.

Kremer, R.J., Caesar, A.J., Souissi, T. 2006. Soilborne microorganisms of euphorbia are potential biological control agents of the invasive weed leafy spurge. Applied Soil Ecology. 32(1):27-37.

Ladenburger, C.G., Hild, A.L., Kazmer, D.J., Munn, L.C. 2006. Soil salinity patterns in Tamarix invasions in the Bighorn Basin, Wyoming, USA. Journal of Arid Environments. 65(2006):111–128.

Last Modified: 10/24/2014
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