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Wrap up from the base at least 3 feet (0.9 m). This will keep the beavers from being able to eat or use the trees. You will need to check your trees to make sure that the beavers are leaving them alone. You can also make wire fences to prevent beavers from entering a specific area (especially around a pond). You can also put mesh coverings over culverts and the like to keep beavers away from them. Sometimes completely destroying the beaver's dam or lodge, as well as eliminating access to its habitat can discourage the beaver. You have to make sure that you carry away all of the dam, so that the beaver can't access it in order to rebuild.  Use a sturdy potato rake and work from the downstream side, to completely destroy the dam or lodge. You will want to keep checking the dam or lodge area to make sure that the beaver is not rebuilding and that there is no material available for rebuilding. There is only one repellant that has been proven to be effective in eliminating beavers and beaver damage. This is Thiram. You'll need to apply the repellant directly to the leaves and shrubs that the beaver has been using as a food source.  Again it's good to use this method in conjunction with the other methods, such as destroying the dams and lodges and then spraying the food sources with Thiram. There are other repellants and sprays you can use to discourage beavers from coming into the area if they haven't already, but only Thiram gets rid of them if they're already there. There are a couple different ways to control the water level so that it doesn't become conducive to beaver habitation. You can create a drain so that the water level stays down or you can keep the water clear of debris or anything that might prevent water flow.  Get a drain pipe by fitting two plastic sewer pipes together and perforate one of them. Depending on the volume of the water in the stream the diameter of the pipes can be 10, 15, 20 or 25 cm (4, 6, 8 or 10 in.). Dig a hole in the beaver dam along the original stream channel. Set three-quarters of the pipe at almost any level in the dam, and extend the perforated edge into the beaver pond (upstream). Attach a weight to one end of the pipe. Allow around one quarter of the pipe to extend out on the downstream side of the dam. Add about a 1 inch elbow or turndown to the perforated side of the pipe so that you discourage plugging of the upstream end of the pipe.

Summary:
Wrap trees with chicken wire or other heavy metal sheeting or wire. Destroy the dam or lodge. Use a repellant. Control the water level.