A decades-long spat with the U.S. over lumber is starting to burn Canadian producers. While the first half of 2018 was marked by record prices, the picture’s now less rosy. …The result: Interfor Corp slashed output by 20 percent at its sawmills in BC… Canfor Corp curtailed output by about 10 percent and West Fraser said it will permanently shut 300 million board feet of capacity. Analysts say more cuts could be ahead. “The bite is significant,” said Susan Yurkovich, chief executive officer of the B.C. Council of Forest Industries. “When you’re in a very low price environment and you’re paying duties you get to a point where you can’t continue to operate.” …“It’s sort of a market that is unsustainably low,” Mason said by telephone. “At some point you’re going to want to stop losing money and we’ll see more downtime unless prices migrate higher.”