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United States Department of Agriculture

Agricultural Research Service


Location: Pest Management Research

2011 Annual Report

1a. Objectives (from AD-416)
Objective 1: Determine proper taxonomic identification and/or knowledge of evolutionary relationships of key emerging invasive plant species, including perennial pepperweed (Lepidium latifolium), Russian olive (Elaeagnus angustifolia), dyer’s woad (Isatis tinctoria), Dalmatian toadflax (Linaria spp.), common tansy (Tanacetum vulgare), oxeye daisy (Leucanthemum vulgare) and their potential biological control agents. (Gaskin and Delaney) Objective 2: Investigate reproductive strategies of key emerging invasive plant species, including perennial pepperweed (Lepidium latifolium) and hawkweeds (Hieracium spp.), and use this information in decision tools for selecting potential biological control agents. Objective 3: Develop insect and pathogen biological control agents, and synergies of these agents, for invasive plants of the Northern Great Plains, including saltcedar (Tamarix spp.), whitetop or hoary cress (Lepidium draba), leafy spurge (Euphorbia esula), and hawkweeds (Hieracium spp.). Objective 4: Investigation of the pathogenicity to native forbs and grasses of Fusarium spp. isolates associated with Tamarix biomass. Objective 5: Determine the effects of biological control on restoration efforts of rangeland and public land and develop restoration protocols that complement future biological control efforts.

1b. Approach (from AD-416)
Exotic invasive weeds cause about $35 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, but improvements in methodology are warranted. We propose that by better understanding invasive plant taxonomy, evolutionary relationships, origins, population structure and reproductive biology, we can identify more effective and lower risk insect and pathogen biological weed control agents. Additionally, understanding ecological interactions between insect and pathogen agents will let us employ their synergistic action. Biological control of weeds is a step towards returning to desired landscapes, with significantly reduced densities of noxious weeds and increased cover of native or other desired species. Establishing desired species cover in previously infested areas may require the application of successful restoration programs. We will examine the ecological and evolutionary processes that maintain desired communities, and then use this knowledge to improve rates of success in restoration. Additionally, successful biological control can leave a legacy of increased inoculum of soilborne pathogens, and we will investigate if this inhibits restoration efforts. This more holistic view of invasive weed management, starting with a better understanding of the basic biology of the invasion, including ecological and evolutionary studies of the biological control and restoration processes, will enhance our ability to replace invaded areas with ecologically sound and economically useful landscapes.

3. Progress Report
This is the report for the new project #5436-22000-017-00D “Reducing the Impact of Invasive Weeds in Northern Great Plains Rangelands through Biological Control and Community Restoration,” which started on February 1, 2011 and replaced the bridging project #5436-22000-015-00D terminated on January 31, 2011. Additional information relevant to the ongoing work associated with this current project includes thirteen published works recorded in old project 5436-22000-015-00D. Russian Olive Invasion: We finished DNA collections of invasive trees in the western USA, and now have a microsatellite library with which we can DNA fingerprint these trees and eventually find their origins in Asia. That information will help us to find effective biological control agents, such as insects and diseases, in the tree’s native range, which can be tested for use in the USA. For the Russian olive restoration project we completed tree removal and performed our first round of vegetation monitoring. The removal resulted in almost zero resprouting and, even at this early stage of the project, our research is impacting regional removal recommendations for this species. Reproductive Strategy of Invasive Weeds: We collected DNA from western USA and European perennial pepperweed populations, and performed our DNA fingerprinting study to determine if the plant reproduces primarily from seed or root fragments. This information will help determine if we need to focus on biocontrol agents that attack roots or seeds. Saltcedar Invasion: We monitored saltcedar attack by biological control agents in WY, but found the tamarisk beetle present only at barely detectable levels. Unprecedented flooding blocked monitoring access to all MT sites, and we still have no known established beetle populations in MT. We are initiating new beetle releases in WY in August. We also analyzed DNA from saltcedar trees at ages spanning from seedlings to 80 years old in a major invasion on the Green River in UT. We found that even the oldest plants, which correlate with the first regional invasion, were novel hybrids of the two main species of saltcedar from Asia. These hybrids may not be as susceptible to biological control as their parental species. Biological Control Using Pathogens: We initiated studies on the effects of soil-borne plant pathogens on post-biocontrol restoration of native forbs and grasses. We discovered two new soil-borne pathogens of invasive hoary cress which can work with root-attacking insects released for biocontrol to increase efficacy. We also achieved unexpectedly rapid progress in disease tests of soil-borne fungi on native forbs when the forbs are in the salty soil under invasive saltcedar trees. Biology of Restoration Plants: We finished experiments on adaptive maternal effects of environment on seed germination rate in Sandberg bluegrass, a commonly used restoration grass. We found that one generation of agronomic production of the bluegrass seed does not affect western wheatgrass germination, but does increase native needle and threadgrass germination under restoration conditions.

4. Accomplishments
1. Removal of invasive Russian olive for habitat restoration. Russian olive is an invasive tree species in wet areas of arid climates in the west. The invasion decreases landscape productivity by reducing forage value and negatively impacting hunting and recreation. Government agencies and land managers are gearing up to control this invasive tree, but studies of best removal and restoration practices are lacking. ARS researchers at Sidney, MT, in collaboration with many government agencies and the National Wild Turkey Federation, investigated best practices for Russian olive removal and revegetation. They identified a method for successful removal with almost no resprouting. The USDA Natural Resources Conservation Service and a chemical company are thus changing their recommendations for tree control and the new method creates savings for land managers by avoiding unnecessary and costly re-spraying of herbicides.

2. Restoration using annual cover crops. Annual cover crops can be planted with perennial grasses so that forage can be immediately available to cattle and soil can be stabilized. However, some land managers have suggested that these annuals might prevent successful establishment of perennials by competing for resources. ARS researchers in Sidney, MT, determined that planting annual cover crops with perennial grasses does not competitively inhibit perennial grass establishment or early growth, and under some conditions they may facilitate perennial establishment. Thus, cover cropping, such as is considered by the North Dakota Department of Agriculture in their recent large pipeline project, is a viable strategy for restoration.

3. Plant invasion found to be clonal. Perennial pepperweed is a noxious weed in many habitats; pastures, deserts, wetlands, salt water estuaries and along rivers of the western and northeastern US. The shrub was thought to be genetically diverse, because it can spread by sexually produced seeds that would typically be different from the mother plant (as happens in humans). ARS researchers in Sidney, MT, used DNA fingerprinting to determine that the invasion contains only three genotypes, not millions of genotypes as was expected. All seed produced is identical to the mother plant it came from, and vast regions only contain one genotype. This is good news for the ongoing perennial pepperweed biological control project, as researchers now don’t have to worry about there being much chance for the invasion to contain genetic resistance to new biological control agents. In fact, ARS researchers have provided the biological control project with three batches of seed, representing all of the US genetic diversity, which will save the project much time and money when compared to testing new biocontrol agents on dozens of accessions of perennial pepperweed from different habitats around the US.

Last Modified: 06/21/2017
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