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Title: Natural enemies of perennial pepperweed, lepidium latifolium L., in its introduced range

item Williams, Livy
item Tonkel, Kirk
item PITCAIRN, MICHAEL - California Department Of Food And Agriculture

Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2014
Publication Date: 5/19/2014
Citation: Williams III, L.H., Tonkel, K.C., Pitcairn, M. 2014. Natural enemies of perennial pepperweed, lepidium latifolium L., in its introduced range. International Symposium on Biological Control of Weeds. p. 132.

Interpretive Summary:

Technical Abstract: Perennial pepperweed, Lepidium latifolium L., is a member of the Brassicaceae native to Eurasia. It was unintentionally introduced to North America in the early 1900s, where it has since spread over millions of acres. This weed is an aggressive invader of wetlands, meadows, roadsides, and agricultural fields where soil conditions are slightly alkaline or saline. Control of this weed presents a challenge: physical and chemical control strategies are generally not effective and have adverse consequences. Biological control is also problematic, due to the relatively close phylogenetic relationship between L. latifolium and cruciferous crops (e.g., broccoli, cabbage, canola) and several native Lepidium species, which could also be impacted by an L. latifolium biological control agent. However, foreign exploration in regions where perennial pepperweed co-occurs with other Lepidium species may nevertheless yield promising candidate agents. A better understanding of the natural enemy complex of perennial pepperweed in its introduced range would help guide future control efforts because it would characterize current levels of suppression, help identify existing natural enemies that might be enhanced, and determine the potential for interference, or perhaps synergistic effects, between candidate agents and natural enemies that are already present. Results of a 3-year study in Nevada and California showed that perennial pepperweed is attacked by several above-ground natural enemies, including weevils, flea beetles, leafhoppers, and white rust. Herbivore attack on L. latifolium roots was rare. Site-specific differences in natural enemy attack were observed. Our results provide baseline information that will aid foreign exploration and agent selection.