S&P fell 0.9% to 3,287.15 in midday trading.
The Dow Jones Industrial Average declined 0.7% to 27,096.11 while the Nasdaq was off 1.6% to 10,787.78.
The yield on a 10-year Treasury bond was trending up 3.5% to 0.687%.
The price of gold was down 2% to $1,869.
A barrel of oil was up 0.5% to $39.98.
Chipotle Mexican Grill Inc. (NYSE: CMG) in Newport Beach rose 4% to $1,285.39 and a $36 billion market cap. The restaurant chain yesterday said it was bringing back its popular steak dish, carne asada, for a limited time. The shares have tripled since their 52-week low in March.
Irvine-based Lantronix Inc. (Nasdaq: LTRX) jumped 8.8% to $4.84 and a $138 million market cap. The company, which makes chip systems for remote management of devices, today unveiled new products for the medical, gaming and retail sectors. Shares have tripled since their 52-week low in March.