2013 Annual Report
1a.Objectives (from AD-416):
Objective 1. Conduct foreign exploration and biological evaluation for biological control agents of weeds of western rangelands such as the annual grass medusahead rye and perennial pepperweed.
Sub-objective 1.1: Conduct foreign exploration for natural enemies of medusahead rye and perennial pepperweed.
Sub-objective 1.2: Conduct host-specificity testing and impact evaluation to assess biological control candidates of target weeds for risk to non-target organisms.
Objective 2. Understand the ecology, biology and genetic variation of invasive weeds such as saltcedar, perennial pepperweed, and medusahead rye, and their natural enemies.
Sub-objective 2.1: Conduct ecological studies of seed predators and other natural enemies of medusahead rye in the native and invaded ranges.
Sub-objective 2.2: Characterize genetic variation of Lepidium latifolium (perennial pepperweed) in its native and invaded ranges.
Objective 3. Determine the effects of integrated weed suppression (particularly saltcedar) and woody plant removal (pinyon and juniper) on ecosystem processes such as water and carbon cycling, and on long-term successional processes (including plants and wildlife), insect impacts on invasion, and restoration processes to facilitate science-based rehabilitation and restoration of lands invaded by these weeds.
Sub-objective 3.1: Long-term monitoring of the effects of Diorhabda carinulata (northern Tamarisk beetle) on ecosystem functions, tree mortality and wildlife populations in areas affected by saltcedar biological control.
Sub-objective 3.2: Determine guidelines for secondary control methods and restoration planning.
Sub-objective 3.3: Determine the effects of two pinyon and juniper removal treatments on the hydrologic budget, particularly soil moisture, as well as understory composition.
Objective 4. Develop restoration methodologies to prevent the invasion of annual grasses (such as cheatgrass, medusahead rye, and/or red brome) following destructive events (such as fire) in rangeland ecosystems.
1b.Approach (from AD-416):
Over the next five years we will conduct research to develop appropriate strategies to control exotic weeds and encroaching native species in western rangelands and riparian areas. Control measures will focus on using classical biological control to find insect enemies of exotic weeds, as well as other control measures, such as mechanical treatments. Genetic analyses of exotic weed species will determine the diversity of populations in the invaded range and identify similar populations in the native range to improve our ability to select effective control agents. There is little research on the ecosystem impacts of control measures; we will determine the impacts of control measures on ecosystem functions including carbon and water cycling, plant community composition and small animal diversity. We will also conduct research to determine appropriate restoration strategies for these ecosystems, by testing planting techniques and novel seed mixtures. These investigations will include basic and applied studies using hypothesis-driven experiments conducted in the laboratory, greenhouse, and field. Formerly 5325-22000-023-00D (June, 2011).
Due to agency-wide restrictions on funding for travel and cooperative agreements, a limited amount of foreign exploration for natural enemies of target weeds in their native ranges and subsequent testing for host-specificity and impact was possible (done in collaboration with colleagues in Europe under project, 5370-22000-023-01S). Studies of the ecology and insect diversity are ongoing in medusahead (Taeniatherum caput-medusae), juniper (Juniperus spp.) and saltcedar (Tamarix spp.). Molecular genetic studies of medusahead and cheatgrass (Bromus tectorum) are continuing. Germplasm from cheatgrass populations was collected across the northern Great Basin for genetic analyses. Cheatgrass specimens with seed-killing smut disease were collected from California, Idaho, and Oregon and sent to collaborators at University of California, Riverside, for identification. Medusahead populations in Nevada were sampled in collaboration with the Nevada Department of Agriculture to survey for the presence of endophytic fungi that may affect medusahead invasiveness. Seed ecology of invasive native juniper species was studied through identification of insect species reared from juniper berries collected in the western Great Basin. In collaboration with US Forest Service, we identified and preserved insect fragments from wood rat middens that are 400-10,000 years old to estimate the impact of pre-industrial climate change on insect species distributions.
In continued work to measure ecosystem effects of saltcedar biological control by the northern tamarisk beetle, Diorhabda carinulata, we measured ecosystem exchanges of carbon dioxide and water, tree mortality and monitored small mammal diversity in response to ongoing herbivory at sites where beetles have been established for multiple years. Wildlife monitoring was mandated as part of the permit for the release of Diorhabda. Annual monitoring of small mammal populations at saltcedar sites undergoing biological control conducted at 3 sites, 2 of which have been monitored since before the beetles were released. One site that was previously monitored was lost as a research site, as biological control has progressed sufficiently that the landowner cleared the site of dead saltcedar trees and put the area back into alfalfa production. This work is essential to continuation of the saltcedar biological control program, which has currently been discontinued by the US Fish & Wildlife Service due to concerns about effects on the endangered southwestern willow flycatcher. We expanded instrumentation in a pinyon and juniper encroached watershed in central Nevada. We added additional instrumentation to monitor the water use of individual trees and sagebrush shrubs. Additionally, we are conducting detailed studies on which water sources these trees use and the ability of these trees to redistribute rainfall. We continued to measure the interactions between native annual species and cheatgrass. ARS scientists completed the field portion of the experiment which assessed the interaction between native annual species and cheatgrass at the level of both the individual and the population under different precipitation regimes.
A model species was identified to study the genetics of eriophyid mite host specificity. The Eriophyidae is a family of plant-feeding mites that is considered to be among the most promising sources of biocontrol agents for invasive annual grasses, due to often extreme host specificity. An ARS researcher in Reno, Nevada, in collaboration with scientists at Adam Mickiewicz University, in Poznan, Poland, discovered a complex of cryptic lineages with broadly divergent host ranges within Aceria tosichella, a species of eriophyid mite that was previously thought to be a monophyletic generalist feeder. By comparing host-acceptance bioassay data with DNA sequence data from populations of A. tosichella collected from a variety of wild and domesticated grass species, lineages were identified with host ranges that varied from highly host-specific to highly polyphagous. In addition to producing results with important agricultural implications (some A. tosichella lineages are worldwide pests of wheat, barley, and other cereals, as well as vectors of cereal diseases), these researchers are developing this species complex as a novel model system to study the evolution and genetics of host-specificity in this family of plant-feeding mites with great potential as biocontrol agents of invasive grasses.
The effects of weather variability were identified for plant establishment. ARS researchers in Reno, Nevada, measured population-level performance of native species when grown in competition with low and high densities of cheatgrass under drought conditions compared to wet conditions. Preliminary data analysis suggests that while restored native populations might be viable in the near-term, they may be less so in the long-term and that seeding native plants in high density cheatgrass sites in dry years has little chance of short- or long- term success. Initial results also suggest that there is a significant interaction between water availability and cheatgrass density such that in wet years, native plants can successfully establish, even where cheatgrass density is high. This has implications for restoration guidelines for both seeding density and seeding timing prescriptions.
The ecosystem effects of pinyon and juniper treatments were identified in Porter Canyon, Nevada. In response to stakeholder concerns, ARS scientists in Reno, Nevada, in conjunction with University Nevada, Reno (UNR), and Smith Creek Ranch established the first instrumented watershed in Nevada to study the effects of timber practices for encroaching pinyon and juniper in areas formerly dominated by sagebrush. There is a high degree of concern over the water use of pinyon and juniper, reductions in viable forage, reductions in sage grouse habitat and the effects of harvesting on the water budget and future plant community composition. In support of this project, the Bureau of Land Management (BLM) conducted a regional environmental assessment that produced the larger scale “Desatoya Mountains Habitat Resiliency, Health and Restoration Project” that will have 32,000 acres of direct treatment. To date, this is the first instrumented watershed in Nevada and this large-scale project has resulted in: a national BLM conservation award to the landholder, Smith Creek Ranch (2010); fostered productive relationships with the BLM, other agencies and University partners; and put the ARS on the forefront of research designed to improve habitat for both the sage grouse and sustainable grazing of livestock.
Bateman, H.L., E.H. Paxton, and W.S. Longland. 2013. Tamarix as wildlife habitat. In: Sher, A., Quigley, M.F., editors. Tamarix: A case study of ecological change in the American west. New York, NY: Oxford University Press. p. 168-188.
Gaskin, J.F., Schwartzlander, M., Hinz, H., Williams III, L.H., Gerber, E., Rector, B.G., Zhang, D. 2013. Genetic identity and diversity of perennial pepperweed (Lepidium latifolium) in its native and invaded ranges. Journal of Invasive Plant Science and Management. 6(2):268–280.
Harizanova, V., Stoeva, A., Rector, B.G. 2012. Host range testing and biology of Abia sericea (Cimbicidae), a candidate for biological control of invasive teasels (Dipsacus spp.) in North America. Journal of Hymenoptera Research. 28:1-11. DOI: 10.3897/JHR.28.3044.
Skoracka, A., Szydio, W., Rector, B.G., Kuczynski, L. 2013. Wheat curl mite, a global pest of cereals, is a complex of biotypes with divergent host ranges and variable pest potential. Biological Journal of the Linnean Society, London. 109:165-180.
Uselman, S.M., Snyder, K.A., Blank, R.R. 2013. Impacts of insect biological control on soil N transformations in Tamarix-invaded ecosystems in the Great Basin, USA. Journal of Arid Environments. 88:147-155.