* Apple biggest drag on S&P, Nasdaq
* Exxon, Chevron fall as crude prices slide
* Valeant slumps as CEO goes on medical leave
* Disney up as latest Star Wars film rakes in $1 bln
* Indexes down: Dow 0.21 pct, S&P 0.34 pct, Nasdaq 0.39 pct (Updates to afternoon)
By Noel Randewich
Dec 28 (Reuters) - Wall Street fell on Monday, hurt by a steep drop oil prices as well as a dip in Apple shares, pushing the S&P 500 back into negative territory for 2015.
The S&P 500 energy sector lost 1.7 percent, easily the worst performer as a 3 percent drop in oil prices led investors to sell unload shares of Exxon Mobil, down 0.7 percent, and Chevron, which fell 1.68 percent.
"It's mostly on crude. That's more the issue than anything else," said Paul Nolte, senior vice president and portfolio manager at Kingsview Asset Management in Chicago.
U.S. stock indexes have closely tracked crude prices in the past several weeks.
Last week, the three major indexes logged their strongest week since mid-November thanks to a short-lived surge in energy stocks. But with Monday's losses, the S&P 500 was down marginally for 2015.
"It's been a real wrestling match this year and some people are okay with the market ending where it is or down a little to give 2016 a little more of a better look," said Frank Davis, director of sales and trading at LEK Securities in New York.
At 1:47 p.m. (1847 GMT), the Dow Jones industrial average was down 0.21 percent at 17,514.47 and the S&P 500 had lost 0.34 percent at 2,053.93. The Nasdaq Composite had fallen 0.39 percent to 5,029.05.
Apple lost 0.94 percent and was the biggest drag on the S&P and Nasdaq. The company's stock has lost 9 percent in the past month with investors worried that annual iPhone sales could decline for the first time in 2016.
Trading volumes are expected be subdued through the week, which is likely to exacerbate volatility.
Valeant was down 10.79 percent after the Canadian drugmaker said Chief Executive Michael Pearson was going on medical leave.
Fitbit rose 4.6 percent after reports that the wearable gadget maker's iOS app was the most downloaded after Christmas, suggesting strong holiday demand.
Dow component Walt Disney gained 1.3 percent after the company's latest Star Wars installment topped $1 billion in ticket sales.
Declining issues outnumbered advancing ones on the NYSE by 2,038 to 981. On the Nasdaq, 1,887 issues fell and 896 rose.
The S&P 500 index showed no new 52-week highs and no new lows, while the Nasdaq recorded 32 new highs and 37 new lows. (Additional reporting by Abhiram Nandakumar in Bengaluru; Editing by Meredith Mazzilli)