General Motors will cut production at a Baltimore plant by a third starting in August and lay off some workers because of declining sales of the minivans the factory builds, Bloomberg News reported. Output of Chevrolet Astro and GMC Safari minivans will drop to more than 200 a day starting on August 4 from more than 300 now, spokesman Dan Flores told the news agency. GM hasn't decided how many of the plant's 1,300 employees will be laid off, he said.