Impressive teenage midfielder Jay Spearing was involved in their two other best attacking moves of the half, firstly forcing keeper Krul into a low save with a 25-yard shot and then later provided a superb pin-point cross from the right which Lucas headed straight at the United keeper from 10 yards out.
Ruth, followed with a decisive pin and, in the second round, capped a string of three straight pins for the Nittany Lions while extending his winning streak to 65.