BISMARCK, N.D., Aug. 4, 2022 /PRNewswire/ — MDU Resources Group, Inc. (NYSE: MDU) today reported second quarter earnings of $70.7 million, or 35 cents per share, compared to second quarter 2021 earnings of $100.2 million, or 50 cents per share. For the six months ended June 30, 2022, MDU…