(Close): A late rally saw the major US indexes end the day in positive territory, just.
Analysts at Wells Fargo Advisors warned the indexes were "signalling another round of profit taking".
DuPont shares fell 3.3% after the company said its second-quarter earnings would be lower than a year earlier and below analysts' forecasts.
The chemicals giant said disappointing corn seed sales and seed inventory write-downs were to blame for the lower earnings forecast.
Elsewhere, Nike shares were 1% higher after it reported earnings late on Thursday that were ahead of analysts' expectations.
The sportswear group reported earnings per share of 78 cents after higher sales offset the impact from a 36% rise in marketing expenses ahead of the World Cup.
Discount retailer Dollar General fell 7.3% after chief executive Richard Dreiling announced his plan to retire in May 2015, or earlier should the company find a successor.