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United States Department of Agriculture

Agricultural Research Service


Location: Pest Management Research

2012 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. BSL-2, 11/12/2010 (PMRU, Sidney, MT); BSL-3, 3/15/2010 (MSU Bozeman, MT).

3. Progress Report:
Invasive hawkweeds: We devised a successful protocol for testing how effective the pathogen Puccinia hieracii from Europe is on its original host populations of meadow hawkweed. Through field studies, we discovered the first occurrence of Pilidium concavum as a soilborne pathogen of meadow hawkweed in Europe. We also developed DNA markers that can distinguish the various species of invasive hawkweed, which are often hard to identify morphologically. This information will help researchers move towards effective biological control agents for this set of invasive weeds. Invasive hoary cress: We initiated field plots at the ARS European Biological Control Laboratory to investigate interactions of the disease Rhizoctonia solani and the candidate biological control agent Ceutorhynchus assimilis, a weevil with high potential as a control agent for invasive weed hoary cress. We now have C. assimilis in our Sidney, MT quarantine facility for rearing. We are also rearing virgin C. obstrictus adults so that we can test if the two weevil species hybridize, which would impair the use of C. assimilis as a biological control agent. Invasive Russian olive: To increase the utility of our study of post-biocontrol of Russian olive restoration project, we added comparison plots in south-central MT, WY, and SD. These plots will be monitored for weed succession and restoration after manual/chemical removal of Russian olive trees. We also conducted a survey of insect fauna in existing Russian olive to determine baseline insect diversity before Russian olive removal. We performed an overwintering study of Russian olive seed to determine loss of seed to herbivores, and viability rate of seeds after one year. We screened our Russian olive DNA microsatellite library and found 12 markers that will help us distinguish the various USA invasive strains, and pinpoint their origins in Eurasia, so that researchers can find potential biological control agents for this noxious weed. Invasive oxeye daisy: Oxeye daisy belongs to a group of more than 14 similar-looking species and ornamental hybrids found in the USA and Eurasia. To distinguish oxeye daisy from other species and ornamentals, we sequenced DNA from over 150 collections of USA and Eurasian plants. This information will determine how many species, genotypes and hybrids are invading the USA, and that information has been passed on to researchers to enhance exploration of biological control agents. Sandberg bluegrass: Our field study on maternal effects in Sandberg bluegrass, a valuable restoration species, has been completed, and plants are now being grown in the greenhouse with and without cheatgrass competition. The initial data collection for research on maternal effects in restoration plantings is almost complete. Commercially-produced seeds had greater germination rates than wild-collected bluegrass seeds. A follow-up experiment to examine the progeny of competition-grown and naïve bluegrass plants has been designed and will be executed this fall.

4. Accomplishments
1. Successful inoculation of invasive hawkweed. Hawkweed is an invasive species for which biological control agents are being sought. ARS researchers in Sidney, MT developed an inoculation method for Puccinia hieracii, a rust found on populations of meadow hawkweed, completing proof of pathogenicity. Successfully developing a means of inoculating hawkweed with spores of this rust is critical to assessment of disease impact to U.S. populations of meadow hawkweed, host range and comparative virulence tests, all important data to support eventual release of the fungus for biological control of this invasive range weed.

2. Molecular identification of invasive knotweed species. Japanese, Giant and Bohemian knotweed species are highly invasive in North America, especially in the Pacific Northwest USA and western Canada. These species hybridize and are thus difficult to distinguish with morphology. Biological control agents currently being developed attack each species, and certain hybrids, but control agents exhibit different levels of efficacy. ARS researchers at Sidney, MT responded to requests by Oregon State University, University of Idaho, and Agriculture and AgriFood Canada to determine the identities of local invasions and distributions of knotweed species across western North America. Molecular tools were used on over 900 plants from 132 locations in nine states and provinces to meet the goal. This information will be used to ensure that representative knotweed genotypes are adequately screened in biological control testing, and that biological control agents are distributed only in regions where they will be effective.

3. Pathogen for invasive hawkweed. Hawkweed is an invasive species for which biological control agents are being sought. ARS researchers in Sidney, MT proved Pilidium concavum, typically a foliar pathogen, to be a root pathogen of European meadow hawkweed. In characterizing an apparent complex of pathogens of meadow hawkweed, Pilidium concavum was isolated from roots of stunted and chlorotic plants in stands of the weed in its native range, and found to cause root lesions in pathogenicity tests. Such findings contribute to a fuller understanding of the diversity of natural enemies limiting the size of hawkweed stands in the native range and thereby improve the basis of more ecologically-informed invasive weed biocontrol.

Review Publications
Piesek, D., Wenda-Piesek, A., Kotwica, K., Lyszczarz, A., Delaney, K.J. 2011. Gastrophysa polygoni herbivory on Rumex confertus: Single leaf VOC induction and dose dependent herbivore attraction/repellence to individual compounds. Journal of Plant Physiology. 168(17): 2134-2138.

Delaney, K.J., Klypina, N., Maruthavanan, J., Lange, C., Sterling, T.M. 2011. Locoweed dose responses to nitrogen: Positive for biomass and primary physiology, but inconsistent for an alkaloid. American Journal of Botany. 98(12): 1956–1965.

Caesar, A.J. 2011. The Importance of Intertrophic Interactions in Biological Weed Control. Pest Technology. 5(Special Issue 1): 28-33.

Delaney, K.J. 2012. Nerium oleander indirect leaf photosynthesis and light harvesting reductions after clipping injury or Spodoptera eridania herbivory: High sensitivity to injury. Plant Science. 185-186: 218-226.

Piesik, D., Wenda-Piesik, A., Ligor, M., Buszewski, B., Delaney, K.J. 2012. Dock leaf beetle, Gastrophysa viridula Deg., herbivory on Mossy Sorrel, Rumex confertus Willd: Induced plant volatiles and beetle orientation responses. Journal of Agricultural Science. 4(1): 97-103.

Caesar, A.J., Lartey, R.T., Caesar, T. 2012. First report of a root and crown disease of the invasive weed Lepidium draba caused by Phoma macrostoma. Plant Disease. 96(1):145.

Gaskin, J.F. 2012. Tamaricaceae. In: Baldwin, B.G., Goldman, D.H., Keil, DJ, Patterson, R., Rosatti, T.J., Wilken, Dieter, D.H., editors. The Jepson Manual: Vascular Plants of California, Second Edition. Berkeley, CA: University of California Press. pp. 1259-1261.

Sainju, U.M., Caesar, T., Caesar, A.J. 2011. Comparison of soil carbon dioxide flux measurements by static and portable chambers in various management practices. Soil and Tillage Research. 118:123-131.

Vallotton, A.D., Murray, L.W., Delaney, K.J., Sterling, T.M. 2012. Water deficit induces swainsonine of some locoweed taxa, but with no swainsonine-growth trade-off. Acta Oecologica. 43: 140-149. Available:

Gaskin, J.F., Birken, A.S., Cooper, D.J. 2012. Levels of novel hybridization in the saltcedar invasion compared over seven decades. Biological Invasions. 14(3):693–699.

Kulpa, S., Leger, E., Espeland, E.K., Goergen, E. 2012. Postfire seeding and plant community recovery in the Great Basin. Rangeland Ecology and Management. 65(2): 171–181.

Gaskin, J.F., Schwarzlaender, M., Williams, L., Gerber, E., Hinz, H. 2012. Minimal genetic diversity in the facultatively outcrossing perennial pepperweed (Lepidium latifolium) invasion. Biological Invasions. 14:1797–1807. Available: DOI.10.1007/s10530-012-0190-4.

Zhang, D., Shi, X., Wang, J., Liu, H., Gaskin, J.F. 2011. Breeding system and its consequence on fruit set of a rare sand dune shrub Eremosparton songoricum (Fabaceae: Papilionoideae): implications for conservation. Journal of Arid Land. 3(4):231-239.

Guermache, F., Rodier-Goud, M., Caesar, A.J., Héraud, C., Claude-Bon, M. 2012. Bi-fluorescence imaging for estimating accurately the nuclear condition of Rhizoctonia spp.. Letters in Applied Microbiology. 54(6): 568–571.

Last Modified: 05/26/2017
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