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.

PLoS ONE

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.

 

Molecular identification and pathogenicity assessment of a rust fungus infecting common ragweed (Ambrosia artemisiifolia) in its native North American range

Citation: Kassai-Jáger E, Seier MK, Evans HC, Kiss L. 2015. Molecular identification and pathogenicity assessment of a rust fungus infecting common ragweed (Ambrosia artemisiifolia) in its native North American range. European Journal of Plant Pathology 145:81-87.

SpringerLink

Abstract: A rust fungus collected from common ragweed (Ambrosia artemisiifolia) in Texas, USA, was identified as belonging to the Puccinia xanthii morphospecies based on its nrDNA ITS sequence. Pathogenicity studies carried out with this rust accession under quarantine conditions in the UK showed that the fungus was highly virulent on A. artemisiifolia plants from Australia. Recently, P. xanthii has been proposed as a potential classical biological control agent (CBCA) for common ragweed in its invasive range, focusing on Europe, despite previous doubts about its biocontrol potential. The results of the pathogenicity tests reported here support the suitability of this pathogen as a CBCA for common ragweed.