Armstrong Tire Co. will close its Iowa plant.

Armstrong, a subsidiary of Armtek Corp., said its Des Moines, Iowa, plant will be closed in six months and 1,050 jobs will be eliminated because attemts to cut costs were unsuccessful. The company said it had needed to reduce the cost of operating the 43-year-old plant to remain competitive with the Firestone Tire & Rubber Co. plant in Des Moines, where workers faced with a similar threat have agreed to wage and benefit concessions.