Republicans chose Charles I. Ecker to take on Howard County Executive Elizabeth Bobo in yesterday's primary, while Democrats dumped an incumbent sheriff for the third primary in a row.

In other races, County Council members Shane Pendergrass (D-District 1) and Charles C. Feaga (R-District 5) defeated a pair of slow-growth candidates who had refused to accept developer donations.

Sandra H. French won one of two nonpartisan positions on the county Board of Education election. Susan J. Cook, a high school PTA president, won the second position. French and Cook will compete in the general election on Nov. 6.

Ecker, the choice of GOP party regulars, easily defeated Mount Hebron businessman Gilbert E. South.

Bobo was able to sit out yesterday's primary because her only Democratic challenger, Thomas Hartman, withdrew from the race not long after declaring his candidacy.

Ecker focused most of his attacks during the primary on Bobo and rarely mentioned South, who lost to the incumbent in 1986. The retired school administrator and former Democrat is expected to pin his hopes to his criticism of the county executive's tax and spending policies. He said last night that growth is not the main issue residents face.

"When I knock on people's doors they are worried about taxes, they are worried about where to put the landfill," Ecker said. "We don't want to cut off our economic development {because} that's going to hurt the taxpayers."

Bobo was confident of her chances last night. "We will run on our record," she said.

Noting that a small bond rating house had given the county its top bond rating, triple-A, Bobo said, "That's virtually unheard of in a county of our size. They must have confidence in what we're doing."

In the sheriff's race, retired police administrator Michael A. Chiuchiolo won easily over incumbent Herbert L. Stonesifer. Democrats voted out an incumbent sheriff in the last two primaries, removing Virginia Donnelly in 1986 and John Votta in 1982.

Stonesifer's defeat is no surprise to party insiders, who have been saying for weeks the incumbent was in trouble over his handling of two deputies accused of Nazi mimicry while on duty.

Stonesifer suspended the deputies with pay and left their fate in the hands of an independent review panel made up of law enforcement officials. Chiuchiolo said the deputies' actions showed that Stonesifer wasn't managing the department properly.

Stonesifer last night offered only two words when asked whether the situation contributed to his defeat: "No doubt."

Chuichiolo will face Republican Richmond Laney, an Ellicott City resident and Westinghouse Electric Co. engineer, in the general election.

Council members Pendergrass and Feaga turned back challenges from William C. Smith and John W. Taylor. Smith and Taylor both were counting on strong grass-roots support for their claims that the incumbents had not done enough to stem the county's growth.

Pendergrass faces a strong general election challenge from Republican Dennis R. Schrader, whom she beat in 1986. Feaga will face Democrat D. Susan Scheidt, a political newcomer who was recruited for the race by Bobo.

James B. Dudley fended off JoAnn C. Branche in a primary for Circuit Court judge. The contest marked the first time there has been a contested race in the county for the position, according to county election officials.

Republican Richard J. Kinlein defeated Joseph Fleischmann in the state's attorney race to take on incumbent Democrat William R. Hymes.

In the Republican primary for Orphans' Court judge, Charles M. Coles Jr., Ronald L. Ledford and Catherine Walters won the nomination to take on three Democrats for the three open seats.