A former associate of Boesky pleaded guilty.

Michael Davidoff, the former head trader for Seemala Corp., a brokerage controlled by stock speculator Ivan F. Boesky, admitted taking part in a scheme to violate the securities law designed to insure that brokerages have adequate capital to meet their obligations. He also admitted trying to conceal the shortfall by putting bogus trades on Seemala’s books during a four-month period last winter. He faces a maximum penalty of five years in jail and $250,000 when he is sentenced March 19.