The recent rout of U.S. Treasury bonds, which has pushed the 10-year yield to a 4 1/2-month high of 2.36 percent, signals bad times ahead for that market, says Larry Hatheway, chief economist at UBS Investment Bank.

The surge in rates "marks a secular turning point for bond markets," he writes in a research note obtained by The Wall Street Journal. "We believe a long-term bear market has commenced."

The market lost its bullishness last Tuesday, when the Federal Reserve signaled that with the economy gaining a bit of steam, it won’t increase its bond purchases as some traders had hoped.

The bull market for Treasurys goes way back. It began after the 10-year yield hit a peak of 15.84 percent Sept. 30, 1981. Almost 30 years later, Sept. 22, 2011, it hit a record low of 1.72 percent.

"Mark that date in your calendars," Hatheway writes. "That is the day the secular bear market in U.S. Treasurys began." UBS raised its year-end forecast for the 10-year yield to 2.7 percent from 2.4 percent.

Without another bond buying program from the Fed, yields will keep rising, many experts say.

But not everyone is as dour as Hatheway.

Pimco bond king Bill Gross tells Yahoo that while the bull market is probably over, “it doesn’t mean the beginning of a bear market.” Indeed, he’s still buying Treasurys for Pimco Total Return Fund.