Oct 21 (Reuters) - U.S. stock indexes opened lower on Thursday as IBM and Tesla fell after their quarterly results, with investors awaiting more reports to see the impact of supply chain disruption and labor shortages on companies. The Dow Jones Industrial Average fell 89.02 points, or 0.25%, at the open to 35,520.32. The S&P 500 opened lower by 3.95 points, or 0.09%, at 4,532.24, while the Nasdaq Composite dropped 16.88 points, or 0.11%, to 15,104.80 at the opening bell. (Reporting by Devik Jain in Bengaluru; Editing by Shinjini Ganguli)