Muskrats, originally native to only two small areas of California, are now widespread in their distribution, where they can cause damage to some crops, but are of particular concern because of their burrowing in structures of irrigation canals and ditchbanks, waterways, and levees. Methods of canal and waterway construction can reduce or prevent damage, as can use of materials that exclude muskrat burrowing. Some materials have been shown to be repellent to muskrat burrowing when used to treat the soil near waterways. Reduction or elimination of weedy plant growth can be a deterrent in situations where no other food sources are nearby. Muskrat populations can be reduced or controlled by use of traps, burrow fumigants, shooting, or use of toxic bait; details of recommendations for use of these methods are included.