Gary Mankulish of Prince Georges Country Club remained the only Washington, D.C., area survivor after today's second round of the U.S. Amateur golf championship at Aronimink Golf Club.

Mankulish defeated H.B. Warren II of Tulsa, Okla., 2 and 1, this morning to complete Wednesday's rain-delayed match. The Maryland and District of Columbia amateur champion then won 5 and 4, over James Rowse of San Jose, Calif.

Mankulish was 4 up at the turn then lost the 10th hole. He captured the 12th and 13th holes with birdies and won the match when the 14th hole was halved.

Mike Toomey of Alexandria, Va., who upset Walker Cup standout Vance Heafner Thursday, lost, 3 and 1, to Charles Van Dyne of Lawrence, Kan. Toomey was 1 down at the turn before losing 13th and 14th. He won the 16th hole but Dyne took the 17th for the victory.

Marty West of Columbia Country Club, Chevy Chase, Md., bowed, 1 up, to Doug Fischesser of Connersville, Ind. Fischesser birdied the par-five, 542-yard 16th hole to take the lead and the remaining holes were halved.

Gary Cowan of Kitchener, Ontario, who won this tournament in 1966 and 1971, ousted Dave King of Bethesda, Md., 4 and 2. Cowan was 4 up after nine and won with a birdie on the 16th hole.

Defending champion Bill Sander defeated Rik Jones, the 1956 NCAA champion, 2 and 1. Scott Simpson and Mike Brannan were among U.S. Walker Cup players who advanced. Peter McEvoy, the British Amateur champion from Birhingham, England, also advanced.

Vinnie Giles of Richmond, Va., the 1972 Amateur champion who has also finished second three times, defeated Dan Croonquist of St. Paul, Minn., 3 and 2.