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Perennial Pepperweed Control in Tidal Wetlands

CLIENT: US Fish & Wildlife Service
PARTNERS: The Bay Institute


Lepidium latifolium, commonly known as perennial pepperweed, is an invasive wetland weed native to various regions of the Eastern Hemisphere.  Believed to have been brought to the U.S. in contaminated seed stock, it is spreading throughout the Western Hemisphere, invading and biologically degrading wetland and marsh habitats.  Once established, this plant is incredibly difficult to remove due to its extensive root structure.  Given that up to 40% of perennial pepperweed's biomass can occur in its roots, and that it is capable of sprouting from very small sections of the root, the plant is virtually impossible to remove on a large scale via mechanical means, though it is susceptible to some herbicide treatments.

In 2005 the U.S. Fish and Wildlife Service began landscape level control of perennial pepperweed throughout the San Pablo Bay National Wildlife Refuge, an important relic tidal salt marsh habitat for the endangered Salt Marsh Harvest Mouse and California Clapper Rail as well as many other species of shorebirds and waterfowl.  After several years of coarse aerial treatments, Shelterbelt was hired in 2010 to provide finer scale control of remaining small stands of perennial pepperweed in sensitive tidal marsh habitat.  Crews used a variety of means to treat the remaining populations, ranging from hiking through the marshes with backpack sprayers, to using a truck-mounted spray rig, to employing small boats to reach stands surrounded by water.  The work required careful identification skills as there were a number of native species with a similar appearance to young perennial pepperweed.


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