Zynga Inc. (ZNGA), maker of the social-networking games “FarmVille” and “Texas HoldEm,” tumbled the most in more than nine months after abandoning plans to enter the online-gambling business in the U.S.

The shares dropped 15 percent to $2.99 at 2:03 p.m. New York time. The stock fell as much as 19 percent earlier in the trading session, marking the biggest intraday decline since October.

“While the company continues to evaluate its real-money gaming products in the U.K. test, Zynga is making a focused choice not to pursue a license for real-money gaming in the U.S.,” the San Francisco-based company said yesterday in a statement. The stock tumbled as low as $2.81.