Do you need to close stream reader in a using block

I have a stream reader inside a using block of code in C#. Do I need to call reader. Close as part of this to close off the process and allow GC to clean up any memory or does it happen on its own? Here is the code that I am using.

using (StreamReader reader = new StreamReader(responseStream))
{
string fileContents = reader.ReadToEnd();
reader.Close();
}