Aug 26 (Reuters) - Canada’s main stock index fell at the open on Thursday, with declines led by energy stocks as oil prices fell on worries about the fast-spreading Delta variant of the coronavirus. * At 9:33 a.m. ET (13:33 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 21.91 points, or 0.11%, at 20,565.41. (Reporting by Shreyashi Sanyal in Bengaluru; Editing by Amy Caren Daniel) Our Standards: The Thomson Reuters Trust Principles.