Location: Pest Management Research
2021 Annual Report
Objectives
Objective 1: Determine the taxonomic identity, origins, evolutionary relationships, reproductive strategies, and/or population genetic information of target invasive weeds, such as bindweed (Convolvulus arvensis), African rue (Peganum harmala), houndstongue (Cynoglossum officinale), leafy spurge (Euphorbia esula/virgata), whitetop (Lepidium draba), and flowering rush (Butomus umbellatus).
Subobjective 1.A: Determine correct taxonomy (Euphorbia complex) and native origins (Euphorbia complex, flowering rush) to support the successful development of classical biological control programs.
Subobjective 1.B: Determine the population structure (flowering rush, African rue, bindweed, Euphorbia complex) and reproductive strategies (bindweed, houndstongue, Euphorbia complex, whitetop) to support the successful development of classical biological control programs.
Objective 2: Improve selection criteria and implementation of biological control agents of the targeted invasive weeds.
Subobjective 2.A: Identify demographic and habitat factors associated with management impacts on Russian olive and whitetop populations.
Subobjective 2.B: Disentangle large-scale variation in agent and weed distributions to improve biological control implementation and integrated weed management of leafy spurge (Euphorbia complex).
Objective 3: Develop effective community restoration technology for disturbed and weed impacted areas.
Subobjective 3.A: Determine priority tools and strategies for effective restoration of riparian ecosystems after Russian olive control.
Approach
Weeds cost U.S. agriculture billions of dollars annually in lost production and control costs. The goal of our project is to decrease weed abundance by increasing the efficacy of biological control agent development and improving the establishment success of plant community restorations that resist invasion. Our team’s research spans multiple aspects of weed control, from taxonomy required for effective development of weed management strategies, demographic and ecological research to optimize biological control management efficacy, and identification of inputs required to support productive invasion-resistant landscapes. We will address critical gaps in genotype-specific information regarding the reproductive strategies, origin and invasiveness of some of the most important invasive weeds in the U.S., thus guiding effective control methods including effective biological control. We will identify ecological and demographic factors limiting invasion potential for weeds targeted for biological control. This will generate strategies to limit target weed spread and provide a general framework of biologically- and ecologically-based weed control methods. We will also create realistic targets for restoration that benefit landscapes. This work develops science-based, economical weed management that reduces costs, promotes food security and minimizes negative environmental impacts of traditional weed control. We focus on rangeland weeds in the Northern Great Plains and extend this research nationally across a range of habitats. By communicating our results through on-going relationships with land management agencies, farmers and ranchers, academic societies, industry and state extension services, this research supports innovative strategies vital to the sustainability and health of U.S. agroecosystems.
Progress Report
Objective 1: ARS scientists in Sidney, Montana, continued DNA analysis of critical invasive species in the western United States and from their putative origins in Eurasia, including Russian knapweed, whitetop, leafy spurge, mullein, common reed, and flowering rush. They are now using molecular markers to determine the correct invasive species identification, major mode of reproduction, as well as specific origin of these invasions. This information is being used to develop more effective foreign biological control agents to fight against invasive plants in the United States.
Objective 2: ARS scientists in Sidney, Montana, continued multi-year field studies and experiments to improve understanding of how plant population characters and environmental conditions influence the probability of sustainable weed management and of biological control (biocontrol) of leafy spurge, whitetop, and Russian olive. The success of this work relies on ongoing engagement through multi-state and stakeholder collaborations that contribute local data and expertise. This work is being used to develop a regional-scale view of how abundance of these three weeds varies across the U.S., and how management tools including biocontrol might be better integrated to increase weed control across varying conditions.
Objective 3: Ten years post-removal and restoration data are currently being collected by ARS researchers in Sidney and Miles City, Montana to determine the impacts of Russian olive restoration on plant and insect communities, pollinators, and floral resources. A census of all species planted in the study and early growing season vegetation data was conducted, and insect, pollinator, and pollinator resources assessed monthly throughout the growing season. Information gathered is being used to assess how Russian olive removal impacts natural communities, and the scale of management required to achieve sustainable and productive control.
Objective 3: New collaborative research between ARS researchers in Sidney and Miles City, Montana, was initiated to assess plant and soil responses to fire and grazing. Fire and grazing shape rangeland plant species composition and productivity directly by biomass consumption and indirectly through small-scale environmental changes like altered soil moisture and temperature and light availability. These changes potentially affect soil microbes as well, which modulate rangeland productivity by altering plant responses and growth patterns. Effects differ among plant species; invasive species might differ from native species in their responses. Understanding mechanisms underpinning differential plant responses can help producers predict plant community and productivity responses to management across a suite of environmental and biological conditions and target management strategies to decrease weeds and increase rangeland health.
Objective 3: Non-native crested wheatgrass forms monocultures on rangeland, preventing native grasses and flowering plants to persist. This leaves large areas of rangeland unattractive to pollinators. ARS researchers in Sidney, Montana, used herbicides and grazing to decrease crested wheatgrass density and then seeded experimental plots with native grasses and flowering plants. Plots with less crested wheatgrass harbored more flowering plants and bees. These data will be used to evaluate methods through which rangeland dominated by crested wheatgrass can be positively restored with increased resources for honey bees and native pollinators.
Accomplishments
1. Origin of invasive flowering rush found. Flowering rush is an aquatic weed from Eurasia that causes economic and ecological damage in lakes and slow waters in the U.S. and is the focus of a multimillion-dollar eradication and management program. Initial results show that the common genotype of flowering rush in the western U.S. is resistant to a proposed biological control agent. ARS researchers in Sidney, Montana, examined the genetics of the invasion and determined that the plants that have invaded the Pacific Northwest originated from the Overijssel Province of the Netherlands. This information will allow researchers to efficiently explore for co-evolved biological control agents that may be effective for control for this invasion.
2. Quantitative assessment of leafy spurge biocontrol. Leafy spurge remains a problematic weed that costs rangeland producers and managers millions in control dollars across North America despite a widely successful biological control program. Few data are available to assess biological control impacts and help managers determine critical supportive measures that could augment biocontrol pressure. ARS researchers in Sidney, Montana, with collaborators, surveyed leafy spurge and biological control agent populations across Montana, North Dakota, and Idaho. The absence of biological control agents was associated with high prevalence of leafy spurge, providing one of the only extensive empirical datasets in North America documenting a signature of biological control efficacy across a wide region. However, high abundance of agents was not consistently related to leafy spurge abundance, suggesting further research directions targeting limitations to efficacy and integrated weed management to augment biological control. This information allows researchers to pinpoint gaps in leafy spurge management, and will improve a widely established and successful biological control program.
3. Creeping juniper responds to fire management. Woody plant encroachment currently impacts more than one quarter of all western rangelands, costing producers over 5 billion dollars during the past 30 years. Juniper species are the most abundant encroachers, often requiring intensive and cost-prohibitive chemical and mechanical removal. ARS researchers from Sidney, Montana, assessed the effectiveness of fire for managing a dominant juniper species in the region by quantifying densities across a series of times-since-fire from 1999-2017. Fire effectively reduced creeping juniper densities, but recovery occurred within 20 years; a fire return interval of <20 years is necessary for effective management. Plant community compositional shifts resulting from fire were short-lived. This information was requested by key stakeholders and provides producers with critical information regarding a cost-effective means for managing creeping juniper and increasing rangeland productivity, while reducing reliance on cost-prohibitive mechanical interventions and chemicals.
4. Fire decreases mesquite persistence. Extensive mesquite encroachment into arid lands worldwide has caused losses in livestock productivity and attendant losses in revenue, wildlife habitat, and local water supplies, requiring intensive chemical and mechanical management. In Texas alone, agencies spent more than $50 million in just 10 years controlling mesquite. ARS researchers from Sidney, Montana, with university collaborators, experimentally assessed mesquite persistence during fire across a range of fire intensities. High-intensity fire caused mortality in 29% of mesquite, while low-intensity fire caused no mortality. In addition, high-intensity fire did not alter soil chemistry or microbes and caused negligible mortality of grass buds for two dominant species. This information, which is accessible to producers via the Great Plains Fire Science exchange, establishes high-intensity fire as a low-cost option for reducing mesquite abundance in rangelands. Texas producers have adopted high-intensity fire as part of their woody-plant management plans.
5. Novel intercropping increases beneficial insects. Wheat is grown every two years with a fallow replacement grown in between the years. Other than some ecosystem services (e.g., erosion control), growers do not gain monetarily from fallow. Thus, some cash crops that can be used as a surrogate to fallow may be a better economic option for growers. Brassica carinata and Camelina sativa are two crops that can be grown in the Northern Great Plains that have shown promise in the biofuel industry and could be utilized as a surrogate to fallow. However, how honey bees and other beneficial insects utilize these crops was unknown. ARS researchers in Sidney, Montana, monitored experimental plots of these crops over two growing seasons for bees and other beneficial insects. Researchers documented 45 native bee species, honey bees, and 24 genera of beneficial wasps on these two new wheat replacement crops. These crops not only monetarily benefit a grower, they also provide resources (pollen and nectar) to a wide variety of beneficial insects.
