Abstract This article examines the various federal and state regulatory schemes in relation to the direct application of pesticides on estuarine tidelands, that part of estuaries covered and uncovered by the ebb and flow of the tides. It examines the proposed use of carbaryl 80 (Sevin) on the Tillamook Bay oyster tidelands to control alleged infestations of mud shrimp and ghost shrimp. The article focuses on the federal pesticide control laws in relation to a state's authority to sanction alternative uses of a federally registered pesticide. After a background of oyster cultivation in Tillamook Bay, the article reviews the authority of the Oregon Fish and Wildlife Commission, which has jurisdiction over the proposed spraying, its 1982 decision to allow the use of Sevin, and the subsequent appeals by three environmental organizations to the Oregon Supreme Court. In particular, the role of the public trust doctrine in Oregon's estuaries is explored regarding the extent to which that doctrine may be applied ...