Modelling the impact of ragweed management meeting

grouppictureA trio representing SMARTER WG1, 2, and the TF Population Dynamics met 1-3 August in Nijmegen, Nefigure effect of mowingtherlands, enforced by a fourth participant through skype.

They worked on the integration of experimental data on roadside mowing regimes into demographic models of ragweed across Europe to project long-term effects of such management.

Preliminary results will be presented at the final SMARTER meeting in Luxembourg.

A small excursion to a nearby park with one of the few Dutch ragweed populations revealed that there were only 10 plants left. They will likely be pulled out by some biologists working nextdoor soon…

Modelling the introduction and spread of non-native species: international trade and climate change drive ragweed invasion

Citation: Chapman DS, Makra L, Albertini R, Bonini M, Páldy A, Rodinkova V, Šikoparija B, Weryszko-Chmielewska E, Bullock JM (2016) Modelling the introduction and spread of non-native species: international trade and climate change drive ragweed invasion. Glob Chang Biol.:22(9):3067-79. doi: 10.1111/gcb.13220.

Wiley Online Library

Abstract: Biological invasions are a major driver of global change, for which models can attribute causes, assess impacts and guide management. However, invasion models typically focus on spread from known introduction points or non-native distributions and ignore the transport processes by which species arrive. Here, we developed a simulation model to understand and describe plant invasion at a continental scale, integrating repeated transport through trade pathways, unintentional release events and the population dynamics and local anthropogenic dispersal that drive subsequent spread. We used the model to simulate the invasion of Europe by common ragweed (Ambrosia artemisiifolia), a globally invasive plant that causes serious harm as an aeroallergen and crop weed. Simulations starting in 1950 accurately reproduced ragweed’s current distribution, including the presence of records in climatically unsuitable areas as a result of repeated introduction. Furthermore, the model outputs were strongly correlated with spatial and temporal patterns of ragweed pollen concentrations, which are fully independent of the calibration data. The model suggests that recent trends for warmer summers and increased volumes of international trade have accelerated the ragweed invasion. For the latter, long distance dispersal because of trade within the invaded continent is highlighted as a key invasion process, in addition to import from the native range. Biosecurity simulations, whereby transport through trade pathways is halted, showed that effective control is only achieved by early action targeting all relevant pathways. We conclude that invasion models would benefit from integrating introduction processes (transport and release) with spread dynamics, to better represent propagule pressure from native sources as well as mechanisms for long-distance dispersal within invaded continents. Ultimately, such integration may facilitate better prediction of spatial and temporal variation in invasion risk and provide useful guidance for management strategies to reduce the impacts of invasion.

Working Group 4 Meeting “Ragweed: impact and management”

The Working Group 4 meeting “Ragweed: impact and management” took place during the 6th European Symposium on Aerobiology held in Lyon, France on 19 July 2016. It brought together members of WG1, WG3 and WG4, as well as representatives of the International Ragweed Society (IRS), the European Aerobiology Society (EAS), the International Association for Aerobiology (IAA), and members of other organisations such as the European Academy of Allergy and Clinical Immunology (EAACI). The meeting took the form of workshop that was open to all participants of the 6th ESA.

Bruno Chauvel gave an interesting talk on the difficult choices that have to be made in managing Ambrosia. Other COST SMARTER members presented their work, such as current trends in Ambrosia pollen distribution in Europe and the accidently introduced biocontrol agent for ragweed Ophraella communa in Italy: its host range and its impact on Ambrosia plants and pollen.  The final part of the afternoon was dedicated to short presentations of posters.

The session ended with a lively discussion on what should be considered “a positive result of good ragweed management“. This discussion is to be continued at the final meeting in September in Luxembourg.

The meeting was held in the historic city of Lyon

The meeting was held in the historic city of Lyon

Letty de Weger

Certified Crop Advisors’ Perceptions of Giant Ragweed (Ambrosia trifida) Distribution, Herbicide Resistance, and Management in the Corn Belt

Citation: Regnier, E. E., Harrison, S. K., Loux, M. M., Holloman, C., Venkatesh, R., Diekmann, F., Taylor, R., Ford, R. A., Stoltenberg, D. E., Hartzler, R. G., Davis, A. S., Schutte, B. J., Cardina, J., Mahoney, K. J. and Johnson, W. G. (2016). Certified Crop Advisors’ Perceptions of Giant Ragweed (Ambrosia trifida) Distribution, Herbicide Resistance, and Management in the Corn Belt. Weed Science 64(2), 361-377.

Weed Research

Abstract: Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitative data regarding its pattern and mechanisms of spread in crop fields are lacking. To address this gap, we conducted a Web-based survey of certified crop advisors in the U.S. Corn Belt and Ontario, Canada. Participants were asked questions regarding giant ragweed and crop production practices for the county of their choice. Responses were mapped and correlation analyses were conducted among the responses to determine factors associated with giant ragweed populations. Respondents rated giant ragweed as the most or one of the most difficult weeds to manage in 45% of 421 U.S. counties responding, and 57% of responding counties reported giant ragweed populations with herbicide resistance to acetolactate synthase inhibitors, glyphosate, or both herbicides. Results suggest that giant ragweed is increasing in crop fields outward from the east-central U.S. Corn Belt in most directions. Crop production practices associated with giant ragweed populations included minimum tillage, continuous soybean, and multiple-application herbicide programs; ecological factors included giant ragweed presence in noncrop edge habitats, early and prolonged emergence, and presence of the seed-burying common earthworm in crop fields. Managing giant ragweed in noncrop areas could reduce giant ragweed migration from noncrop habitats into crop fields and slow its spread. Where giant ragweed is already established in crop fields, including a more diverse combination of crop species, tillage practices, and herbicide sites of action will be critical to reduce populations, disrupt emergence patterns, and select against herbicide-resistant giant ragweed genotypes. Incorporation of a cereal grain into the crop rotation may help suppress early giant ragweed emergence and provide chemical or mechanical control options for late-emerging giant ragweed.

Is There Any Evidence for Rapid, Genetically-Based, Climatic Niche Expansion in the Invasive Common Ragweed?

Citation: Gallien, L., Thuiller, W., Fort, N., Boleda, M., Alberto, F. J., Rioux, D., Laine, J. and Lavergne, S. (2016). Is There Any Evidence for Rapid, Genetically-Based, Climatic Niche Expansion in the Invasive Common Ragweed? PLoS ONE 11(4), e0152867.


Abstract: Climatic niche shifts have been documented in a number of invasive species by comparing the native and adventive climatic ranges in which they occur. However, these shifts likely represent changes in the realized climatic niches of invasive species, and may not necessarily be driven by genetic changes in climatic affinities. Until now the role of rapid niche evolution in the spread of invasive species remains a challenging issue with conflicting results. Here, we document a likely genetically-based climatic niche expansion of an annual plant invader, the common ragweed (Ambrosia artemisiifolia L.), a highly allergenic invasive species causing substantial public health issues. To do so, we looked for recent evolutionary change at the upward migration front of its adventive range in the French Alps. Based on species climatic niche models estimated at both global and regional scales we stratified our sampling design to adequately capture the species niche, and localized populations suspected of niche expansion. Using a combination of species niche modeling, landscape genetics models and common garden measurements, we then related the species genetic structure and its phenotypic architecture across the climatic niche. Our results strongly suggest that the common ragweed is rapidly adapting to local climatic conditions at its invasion front and that it currently expands its niche toward colder and formerly unsuitable climates in the French Alps (i.e. in sites where niche models would not predict its occurrence). Such results, showing that species climatic niches can evolve on very short time scales, have important implications for predictive models of biological invasions that do not account for evolutionary processes.