The Canadian dollar tumbled to a three-week low during trading on Monday (October 26th) as crude oil prices retreated from a yearly high.In the US forex trading session, the loonie, as the Canadian dollar is known, dropped 1.5 per cent against the US dollar, with a statement from Bank of Canada governor Mark Carney also stifling buying activity.The central bank head reiterated concerns that the Canadian currency had grown too strong and is becoming a threat to sustained economic recovery.Speaking to Bloomberg, Paul Ferley, assistant chief economist in Toronto at Royal Bank of Canada, the nation's biggest bank, said that the depreciation of the loonie could be attributed to concerns about imminent policy decisions."The bank made it quite clear that they didn't think economic conditions warranted moving ahead with any interest-rate hikes," he said.Trading activity in the loonie was also heavily influenced by wider downward movements in crude prices, which slipped further from the $82-a-barrel mark achieved last week.