Lepidium latifolium L. (perennial pepperweed, LEPLA) is an exotic invader throughout western North America. At Malheur National Wildlife Refuge (MNWR) in southeast Oregon, it has invaded about 10% of meadow habitats that are important for wildlife. This study's objective was to determine the most effective and least environmentally harmful treatment to control this weed and restore native vegetation using integrated pest management techniques. During summer 1995, nine 0.24-ha plots in three meadows infested with L. latifolium at MNWR were randomly assigned to a treatment with metsulfuron methyl herbicide, chlorsulfuron herbicide, disking, burning, herbicide (metsulfuron methyl or chlorsulfuron) then disking, herbicide (metsulfuron methyl or chlorsulfuron) then burning, or untreated. Changes in L. latifolium ramet densities and basal cover of vegetation, litter, and bare soil were evaluated in 1996 and 1997. Sheep grazing was evaluated as a treatment for reduction in flower production along roadsides and levees during summer 1997. Revegetation treatments of seeding, transplanting or natural (untreated) revegetation were attempted at plots treated with chlorsulfuron, disking, chlorsulfuron then disking, and at untreated plots from October 1996 through September 1997. Chlorsulfuron was the most effective control treatment with greater than 97% reduction in L. latifolium ramet densities two years after treatment. Metsulfuron methyl was an effective control (greater than 93% reduction) for one year. Disking was ineffective. Burning was ineffective at the one site where sufficient fine fuels existed to carry fire. Herbicide treatments were associated with increased grass and reduced forb cover. Disking was associated with reduced grass and litter cover. Disking combined with either herbicide treatment was associated with reductions in all plant cover (49 to 100%), increased bare ground, and invasion by other weedy species such as Cirsium arvense (L.) Scop. (Canada thistle, CIRAR) and Bromus tectorum L. (cheatgrass, BROTE). Ungrazed L. latifolium averaged 4513 flowers per ramet. Sheep grazing reduced L. latifolium flower production by at least 98%. Revegetation treatments were unnecessary in sites treated with chlorsulfuron and were ineffective at all treatment sites.

This is the first comprehensive identification manual for aquatic and riparian weeds west of the Rocky Mountains. This practical, easy-to-use guide covers 171 aquatic plant species -- consisting of 58 plant groups, including a full description of 82 species and another 96 plants compared as similar species, representing 42 plant families. Lavishly illustrated with over 560 photographs and weighing in at 442 pages, this is a “must-have" reference and field manual for weed control specialists, land managers, water system managers, rice growers, golf course superintendents, and landscape professionals. Anyone interested in learning more about identification of important weeds of aquatic and riparian systems should make room on their bookshelf for this guide.