DALLAS – The peak spring home-selling season is off to a slow start, builder D.R. Horton Inc. said Tuesday, another sign that bad times in the housing market may last longer than expected. Horton, the nation’s largest homebuilder by deliveries, said Tuesday that its sales order in the most recent quarter fell 37 percent, led by even steeper declines in California and the Southwest. The grim report trumped recent indications that sales of homes, especially existing houses, had been improving. “It appeared demand had stabilized, but this throws that into question,” said Bernard Markstein, an economist for the National Association of Home Builders. Horton and other builders have been forced to throw in incentives to generate sales. They have also reduced the number of homes under construction, dumped lots and backed out of options for new land. Shares of Horton were traded down 34 cents or, 1.54 percent, to close at $21.70 Tuesday on the New York Stock Exchange. They have traded in a 52-week range of $19.52 to $35. Experts said some of the factors that overheated housing markets in the past several years – especially easy financing for buyers with marginal credit and growing use of zero-down loans to afford pricey houses – were coming back to haunt builders. People who bought homes at low teaser interest rates are now seeing their monthly payments soar. Many of them can’t afford the new payments nor can they refinance under today’s tougher underwriting standards. “These people are now putting those homes back on the market. Most of them are nearly new homes, and they’re competing with the builders,” said Bruce Norris, a longtime real estate investor in Riverside. “This is not a solvable problem anytime soon,” Norris said. “It’s going to run its course,” which he predicted won’t be over until 2010. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! Horton’s founder and chairman, Donald R. Horton, said that conditions for selling homes “continue to be challenging in most of our markets,” as the supply of unsold new and existing homes remained high. “We continue to sell more homes than any other builder, even though the spring selling season has not gotten off to its usual strong start,” he said. The Fort Worth-based company said net sales orders for the quarter ended March 31 totaled 9,983 homes, down from 15,771 a year ago. The value of the orders dropped 40 percent, to $2.6 billion from $4.4 billion a year ago. The decline in orders was sharpest in California, plunging 59 percent to 1,107 from 2,697 a year earlier. Orders in the Southwest fell 39 percent. The smallest decline: 21 percent in the Northeast. The weak quarter followed a 23 percent drop in orders during the last three months of 2006.