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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICALLY AND ECOLOGICALLY BASED KNOWLEDGE FOR INTEGRATED WEED MANAGEMENT SYSTEMS Title: Mutualism between common earthworm (Lumbricus terrestris) and giant ragweed (Ambrosia trifida) varies between Ohio and Illinois

Authors
item Davis, Adam
item Regnier, Emilie - THE OHIO ST UNIVERSITY
item Harrison, Kent - THE OHIO ST UNIVERSITY
item Liu, Jianyang - THE OHIO ST UNIVERSITY
item Schutte, Brian - THE OHIO ST UNIVERSITY
item Luschei, Ed - UNIVERSITY OF WISCONSIN

Submitted to: Weed Science Society of America Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 17, 2007
Publication Date: February 20, 2008
Citation: Davis, A.S., Regnier, E., Harrison, K., Liu, J., Schutte, B., Luschei, E. 2008. Mutualism between common earthworm (Lumbricus terrestris) and giant ragweed (Ambrosia trifida) varies between Ohio and Illinois. Weed Science Society of America Meeting Proceedings. 47(1):63.

Interpretive Summary: In previous work, burial of giant ragweed seeds by common earthworm in central Ohio (OH) was found to protect them from being eaten after dispersal from the mother plant. The objective of this study was to examine the association between these species across the geographic area where giant ragweed is most troublesome in field crops. A survey of giant ragweed and common earthworm co-occurrence was performed in 2007 at 8 no-till soybean fields in central Illinois (IL) and OH. At all fields, giant ragweed and common earthworm occurred together more frequently, and the proportion of giant ragweed seedlings germinating within middens was greater, than would be expected if the two were randomly associated. However, the association between the species was weaker in IL than OH, with less than 30% of giant ragweed seedlings emerging from middens in IL, compared to more than 80% in OH. Differences in the strength of the association were not explained by earthworm behavior or soil properties in the two study areas. Better understanding of the mechanisms underlying this interaction may help identify management practices that retain soil-improvement activities of earthworms while reducing their facilitation of giant ragweed seedling recruitment.

Technical Abstract: Seed caching of giant ragweed by common earthworm has been found to contribute to giant ragweed recruitment success in Ohio (OH) by protecting the seeds from postdispersal predation at a depth in the earthworm midden that is also suitable for germination. The objective of this study was to quantify the strength of the giant ragweed/common earthworm association in the geographic area where giant ragweed is most troublesome in field crops. A survey of giant ragweed and common earthworm co-occurrence was performed in 2007 at 8 no-till soybean fields in central Illinois (IL) and OH where giant ragweed had been observed previously. At all fields in both IL and OH, giant ragweed and common earthworm occurred together more frequently, and the proportion of giant ragweed seedlings germinating within middens was greater, than would be expected if the two were randomly associated. Although the association between giant ragweed and common earthworm existed in both IL and OH, less than 40% of giant ragweed seedlings germinated within middens at the IL sites, whereas over 80% of giant ragweed seedlings germinated within middens at the OH sites. The difference in the strength of the association was not explained through comparative assays of earthworm seed caching behavior or soil physical resistance to seedling germination in IL and OH. The mutualism between giant ragweed and common earthworm appears to facilitate the invasion of no-till agricultural fields by giant ragweed in a large geographic area within the north central region. Better understanding of the mechanisms underlying this interaction may help identify management practices that retain soil-improvement activities of earthworms while reducing giant ragweed seedling recruitment.

Last Modified: 12/27/2014
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