The 'charge' for treason IS "treason.".
TREASON - A betrayal, treachery, or breach of allegiance. The Constitution of the United States, Art. III, defines treason against …the United States to consist only in levying war against them, or in adhering to their enemies, giving them aid or comfort. This offense is punishable by death..
See: http://www.lectlaw.com/def2/t103.htm (MORE)