July 2 (Reuters) - Wall Street's main indexes opened lower on Tuesday as megacap stocks retreated after a strong session, with additional caution creeping in ahead of jobs opening data and comments from Federal Reserve Chairman Jerome Powell later in the day.

The Dow Jones Industrial Average fell 61.27 points, or 0.16%, at the open to 39,108.25. The S&P 500 opened lower by 13.25 points, or 0.24%, at 5,461.84, while the Nasdaq Composite dropped 71.26 points, or 0.40%, to 17,808.04 at the opening bell. (Reporting by Ankika Biswas in Bengaluru; Editing by Maju Samuel)