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United States Department of Agriculture

Agricultural Research Service

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Location: European Biological Control Laboratory

2012 Annual Report

1a. Objectives (from AD-416):
Objective 1: Characterize the basic biology of target weeds, such as hoary cress, swallow-worts, medusahead, and guineagrass, and their natural enemies. Sub-objective 1.A. Characterize the genetic diversity and basic biology of target weeds and determine their regions of origin. Sub-objective 1.B. Conduct foreign exploration in Europe, Asia, and Africa for natural enemies of U.S. target weeds. Objective 2: Elucidate plant-natural enemy interactions and identify potential candidates for U.S. introduction. Sub-objective 2.A. Conduct preliminary host-specificity and effectiveness testing and facilitate U.S. introduction through prioritization and rearing of agents for target weeds, including, but not limited to giant reed, and swallow-worts. Sub-objective 2.B. Evaluate plant-insect interactions in evolutionary and ecological contexts – the role of visual ecology in host plant finding, selection and acceptance by candidate agents; evolution of differential host specificity in a biological control agent; efficacy of multiple vs. single weed biological control agents.

1b. Approach (from AD-416):
We have adopted a “weed management pipeline” approach to our research that answers essential questions for successful classical biological control. A significant focus of this research is aimed at understanding the basic biology of target weeds, especially characterization of the genetic diversity of targets in their native and adventive ranges. This work will help identify the target’s region of origin, as well as the region(s) from which populations of the target have been introduced into the U.S. Foreign exploration for natural enemies will be conducted concurrently with these studies on target biology; this exploration will provide candidate biological control agents for the following studies. These investigations address target weed-natural enemy interactions, which will include host-specificity and effectiveness testing to facilitate introduction to the U.S., as well as experiments aimed at developing a mechanistic understanding of the evolutionary, ecological, and physiological factors of plant-insect interactions relevant to weed biological control. Successful control of a target weed usually requires decades of research effort, and the research proposed here will be an important step towards ecologically-rational management of some of the most important invasive weeds in the U.S.

3. Progress Report:
Progress was made on both objectives and their subobjectives. Under subobjective 1a, we developed neutral inter-sample sequence repeats (ISSRs) for silverleaf nightshade and began genetic analyses to compare native populations to Greek populations. We obtained samples of native populations from Mexico and Arizona. Results suggest that Greek populations of silverleaf nightshade are the result of multiple introductions. We continued to analyze sequences of two chloroplast regions in Guinea grass (modern African and Texan samples), as well as historical specimens in the CIRAD collection, some dating back to 1944. Samples of giant reed infested by a leaf mining cecidomyiid fly were collected to inventory fungi present in the fly’s galleries to identify a possible insect-fungal symbiosis. DNA extraction yielded 16 species (51 strains) of fungi from 25 localities in Spain, France, Sicily, and Crete. Under subobjective 1b, we conducted foreign exploration in Ukraine to collect medusahead seeds; these seeds were included in a host specificity study that evaluated the impact of a smut using native and North American medusahead seeds. Our rangeland weed research is supported by Projects 0212-22000-023-10R and 013R (USDI-BLM) and 023-14S (BBCA in Italy). We continued mass collections of two giant reed biological control agents in Spain and France for shipment to our collaborator in Texas. More than 5 million specimens were shipped, and one of the agents is now well-established in the Rio Grande Valley. American Farm School MOU 0212-22000-023-11M gives our Greek substation lab and office space, facilitating exploration and field work in the Balkans. We initiated work at our Greek substation to evaluate epidemiology of plant diseases on Canada thistle, milk thistle, and silverleaf nightshade. Under subobjective 2a, we made significant progress toward understanding plant-herbivore trophic relationships, insect oviposition and feeding behavior, and bionomics. A field experiment was conducted in Turkey to evaluate damage by a chloropid fly on medusahead seed production; this is a newly discovered host association for the fly. Host specificity, life history, and behavioral studies were conducted with two potential biocontrol agents of swallow-worts; one of these insects shows promise for future swallow-wort control. Host specificity and dispersal tests were conducted with a psyllid, a potential biocontrol agent of French broom, under field conditions at EBCL. A petition for release of a candidate agent of hoary cress was submitted. Field studies were conducted to identify and evaluate the factors affecting leafy spurge invasiveness, and develop an integrated control strategy for this weed. Research was planned to study the impact of a chloropid fly on common reed at our Greek substation. Under subobjective 2b, we began characterizing spectral reflectance curves of weeds to be used in future host finding studies. We developed microsatellites for a weevil that is a potential biocontrol agent of hoary cress and shipped weevil samples to our ARS collaborator. We established a field experiment to assess Rhizoctonia-weevil-hoary cress interactions.

4. Accomplishments

Review Publications
Berner, D.K., Smallwood, E.L., Cavin, C.A., Eskandari, F., Tunali, B., Buyuk, O., Yildirim, A., Mukhina, Z., Kolomiets, T., Matveeva, T., Bogomaz, D., Kassanelli, D., Souissi, T., Mejri, D., Latiri, K., Kashefi, J., Lagopodi, A. 2011. Mutual benefits through formalized international collaboration on biological control of weeds with plant pathogens. Tunisia Journal of Plant Protection. 6(1):49-74.

Bon, M., Guermache, F. 2012. First report of black swallow-wort as an alternate host of the two-needle pine stem rust pathogen, Cronartium flaccidum (Alb & Schwein.) G. Winter, in France. Plant Disease. 96 (4),585.

Williams III, L.H., Hagler, J.R., Tonkel, K.C. 2011. Retention of immunolabels by Diorhabda carinulata (Coleoptera: Chrysomelidae), a biological control agent of saltcedar. Entomologia Experimentalis et Applicata. 141:154-162.

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.

Guggisberg, A., Welk, E., Sforza, R., Horvath, D.P., Anderson, J.V., Foley, M.E., Rieseberg, L.H. 2012. Invasion history of North American Canada thistle, Cirsium arvense. Journal of Biogeography. 39/10:1919-1931. doi:10.1111/j.1365-2699.2012.02746.x.

Guermache, F., Rodier-Gaud, M., Caesar, A.J., Heraud, C., Bon, M. 2012. Bi-fluorescence imaging for estimating accurately the nuclear condition of Rhizoctonia spp.. Letters in Applied Microbiology. 54, 568-571. doi:10.1111/j.1472-765X.2012.03245.x.

Last Modified: 10/16/2017
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