Project : USDA ARS

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Research Project: Biological Control and Habitat Restoration for Invasive Weed Management

Location: Pest Management Research

2023 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 (African rue, bindweed, houndstongue, Euphorbia complex) and reproductive strategies (bindweed, Euphorbia complex) ) and hybrids (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. Objective 3.B: Determine impacts on pollinator communities after renovation of exotic cool season grasses to functional CRP.

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 researchers at Sidney, Montana, continued DNA analysis of critical invasive species in the western United States and from their putative origins in Eurasia, including whitetop, leafy spurge, teasel, common crupina, common reed, bindweed, and flowering rush. We are now using molecular markers to determine the correct invasive species identification, major mode of reproduction, as well as specific origin of these invasions. These data are informing the development of more effective foreign biological control agents and integrated weed management programs to fight against invasive plants in the U.S. Objective 2: Effective weed management with biocontrol requires targeting vulnerable stages of a weed’s life cycle. Experimental field populations help us to understand the impacts of biocontrol, as we often lack the basic biological data necessary to model and predict outcomes over time and with additional management strategies. In collaboration with university, federal, tribal, and ARS partners, we are using transplant experiments, seed additions, and common garden manipulations to examine how environmental and ecological interactions affect the degree to which insects and pathogens limit the persistence and population growth of whitetop/hoary cress, Russian olive, leafy spurge, flowering rush and common crupina. These data will lead to better quantitative models and predictions of biocontrol impacts, recommendations, and best practices for weed biocontrol, and expand integrated management options for low-input rangeland systems. We completed a multi-year survey of leafy spurge abundance and biological control agent communities across North Dakota, Montana, and Idaho. These data not only address the status of the leafy spurge biological control program in the northern Great Plains and intermountain West, but also provide critical information on agents such as Oberea erythrocephala that were released early in the program, but are only now accumulating potentially effective abundance in the landscape. Overall, this work is providing crucial insight on where biocontrol is most effective, what agents are the most damaging, and how biocontrol management can be improved across a broad range of the most highly invaded region in the U.S. Leafy spurge remains a highly problematic weed throughout the western U.S. and flowers for an extensive portion of the growing season. Numerous pollinating insects, including honey bees, are attracted to the flowers for pollen and nectar. However, no data are available to assess which pollinating insects are utilizing leafy spurge flowers, and how the extent and removal of leafy spurge infestations might influence pollinator populations. ARS researchers in Sidney, Montana, surveyed leafy spurge via sweep netting for pollinators within leafy spurge populations across Montana, North Dakota, and Idaho. Numerous pollinating insects have been found visiting leafy spurge and these insects have now been identified to the lowest taxonomic level possible. These data will be used to evaluate how leafy spurge competes with native range plants for pollination services and the consequences for honey bees and native pollinators. New collaborative research was initiated by ARS researchers in Sidney, Montana, and the U.S. Forest Service managers at Dakota Prairies to assess the potential for a secondary invasion by leafy spurge and other weeds and reinvasion by Juniperus spp. following mastication and fire management. Woody plant encroachment currently impacts more than one quarter of all western rangelands, costing producers over 5 billion dollars over the past 30 years. Juniper species are the most abundant encroachers, often requiring intensive and cost-prohibitive chemical and mechanical removal. While fire is one of the most effective management strategies for reducing juniper abundance, it is not always embraced as a management option. This research will provide critical information on the potential for mastication to serve as a surrogate for prescribed fire in managing native woody invaders in rangelands of the northern Great Plains. Objective 3: ARS researchers at Sidney and Miles City, Montana, are using a ten-year post-removal and restoration experiment to examine the impacts of Russian olive invasion and post-removal restoration on plant and insect communities, pollinators, and floral resources. Russian olive removal and restoration treatments led to persistent differences in plant community composition compared to untreated plots still invaded by Russian olive. After Russian olive removal, planting native species increased native perennial grass cover and decreased invasive perennial grass cover relative to unplanted controls, but restoration planting had no impact on annual invasive grass, native forb, or non-native forb cover. 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. It is unknown how removing Russian olive within riparian zones and re-planting native plants may affect native pollinators. ARS researchers in Sidney, Montana collected native bees from experimental Russian olive removal plots along the Yellowstone River in southeastern Montana. These insects have been processed and are currently being identified with the assistance of ARS taxonomists at Logan, Utah, and Washington State Department of Agriculture. This insect community survey, using colored pan traps over the course of two growing seasons, will provide a baseline for how native bee communities respond to Russian olive removal. Collaborative research between ARS researchers at Sidney and Miles City, Montana, assessing sagebrush response to prescribed fire shows preliminary differences in mortality of resprouting sagebrush species with dormant and growing season prescribed burns. However, in the northern Great Plains, there is concern regarding fire’s impact on sagebrush, which provides important habitat for grassland wildlife species. Additional research will assess the impact of fire return interval and invasive annual grass fuel on resprouting and non-resprouting sagebrush species, as well as the potential for prescribed fire to control Russian olive seedling spread into rangelands. This research will provide information on fire frequencies, seasonality, intensity, and spatial application compatible with maintaining healthy sagebrush populations in cheatgrass-invaded rangelands. This knowledge is critical to developing fire management plans for invasive species that increase overall ecosystem health and ecosystem service delivery.

Accomplishments
1. Solar energy development impacts on pollinator and arthropod communities. Developing solar facilities with minimal ecosystem disruption has become a nationwide priority. ARS investigators in Sidney, Montana, and collaborators have conducted some of the first studies documenting the impacts solar energy development has on multiple arthropod groups, including pollinators. Physical disturbances such as site preparation activities can lead to habitat loss, particularly for non-bee flower visitors, and sustainable decision-making requires more information at the intersection of ecological planning and technology development. Consequently, ARS Sidney, Montana, and collaborators from multiple universities were recently awarded a Department of Energy grant that will be exploring further impacts on native bee pollinators and how eDNA can potentially be used for monitoring native bees within solar facilities to aid in adaptive management solutions to minimize pollinator declines.

2. Identifying targets to improve field bindweed control. Field bindweed is a declared noxious weed or regulated species in 22 U.S. states and 5 Canadian provinces. Management includes cultivation, herbicides, and biological control, but this plant remains difficult to control in a variety of habitats and is a priority problem for organic production systems. New candidate arthropod species are being investigated for classical biological control of field bindweed, but evaluating their potential for impact requires understanding the genetic variation and reproduction strategies among North American populations. ARS researchers in Sidney, Montana, found that different genetic lineages tended to be dominant in eastern versus western bindweed populations in western North America, but variation among populations was too high to predict genetic differences based on location. Many populations reproduced by both seed and vegetative spread, but some populations reproduced entirely through rhizome expansion and without seeds. Thus, proposed biological control agents that target roots and reduce vegetative reproduction may substantially limit spread of this noxious weed, providing additional non-chemical control options to bolster integrated weed management programs for bindweed control in both traditional and organic production systems.

3. New biocontrol agent for flowering rush. Flowering rush is a highly invasive aquatic weed affecting waterbodies and waterways across North America. ARS researchers at Sidney, Montana, are leading the first North American quarantine rearing program, in collaboration with Agriculture and Agri-Food Canada and the Centre for Agriculture and Bioscience International, for Bagous nodulosus, a new candidate biological control agent recently permitted for field release in Canada. Initial colony establishment has been successful, and a first generation of lab-reared insects have been shared with Canadian colleagues to develop additional rearing and research populations in anticipation of release programs. If permitted for release in the U.S., these agents have the potential to reduce the cover and abundance of flowering rush infestations and enhance water, irrigation, and recreation resources.

4. Soil responses to fire management of invasive species. Prescribed fire is an important tool for decreasing invasive grasses in rangelands and restoring ecosystem services delivery. However, fire will not be broadly adopted as a management practice if there are negative repercussions for soil health. ARS researchers at Sidney and ARS Miles City, Montana, collaborated to assess the impacts of prescribed burning for crested wheatgrass and Kentucky bluegrass management on plant available nitrogen and soil microbial biomass and composition. Prescribed fire consistently increased plant available nitrogen in the short term and did not alter the abundance or community composition of soil microbes. These data demonstrate that prescribed fire management promotes grassland nutrient cycling and release, providing a low-cost management option to reduce invasive species abundance while simultaneously enhancing soil health.

5. Identifying collection methods for pollinator assessments. Collection methods for native bees and especially non-bee pollinators are poorly understood. These collection method uncertainties make monitoring native pollinator communities challenging, and stymies efforts to quantify the effects of conservation and land management practices on pollinator communities and pollination services. ARS researchers in Sidney, Montana, compared the pollinator communities surveyed using blue vane traps, colored pan traps, and sweep netting, and how employing different collection methods affected our detection of native bees and other pollinating insects. This is one of the first comparisons of collection methods for non-bee pollinating insects. Such data are critical for improving best practices to efficiently and adequately collect and monitor native pollinators.

6. Managing crested wheatgrass with fire and grazing. Crested wheatgrass is one of the most abundant and widespread invasive species in the northern Great Plains. It reduces native species diversity and may reduce invaded grassland productivity over the long-term as it has lower root biomass than native species, reducing the amount of nitrogen and carbon in grassland soils over time. ARS researchers in Sidney and Miles City, Montana, conducted a study assessing the potential for combined fire and grazing to manage crested wheatgrass invasions. Continuous grazing, with and without burning, as well as rotational grazing with burning reduced crested wheatgrass biomass. While there was slightly lower native bunchgrass biomass in burned plots than unburned plots, there was also an increase in photosynthesis in burned plots, which lasted longer after onset of drought for native species than crested wheatgrass. This shows potential for the combination of fire and grazing to enhance native grass competition with crested wheatgrass, providing a low-cost solution for reducing crested wheatgrass monocultures, enhancing native plant diversity, and increasing forage quality in crested wheatgrass infested stands since crested wheatgrass is poor forage for cattle.

U.S. DEPARTMENT OF AGRICULTURE

Pest Management Research: Sidney, MT