(Adds investor quotes and details throughout; updates prices) * TSX ends down 160.46 points, or 0.8%, at 21,037.07 * Rises 4.8% in October * Financials fall 1.4%; materials end 1.6% lower * Imperial Oil declines 7.1% TORONTO, Oct 29 (Reuters) - Canada’s main stock index retreated on Friday as indications that supply chain disruptions could weigh on the corporate earnings outlook weighed on investor sentiment, but the index still notched its biggest monthly gain since last November. The Toronto Stock Exchange’s S&P/TSX composite index ended down 160.46 points, or 0.8%, at 21,037.07. “The setup from overnight trading coming into this morning was negative based on some of the (U.S.) earnings reports that we saw,” said Allan Small, senior investment advisor of the Allan Small Financial Group with iA Private Wealth. Shares of Apple Inc and Amazon.com Inc dropped after disappointing quarterly earnings and warnings that supply-chain disruptions could weigh on the current holiday sales quarter. Wall Street seesawed before closing with modest gains. The Canadian economy most likely underperformed expectations in the third quarter amid ongoing supply chain woes and a brutal drought, official data suggested. Canadian financial shares fell 1.4%, while the materials group, which includes precious and base metals miners and fertilizer companies, lost 1.6%. Spot gold was down 0.9% at about $1,782 an ounce. For October, the Toronto market was up 4.8%, as higher oil prices boosted energy stocks and rising bond yields boosted prospects for bank profit margins. “Whenever you have a scenario like that it really bodes well for the TSX,” said Allan Small, senior investment advisor of the Allan Small Financial Group. Energy and financials combined account for 45% of the Toronto market’s value. Imperial Oil Ltd said its third-quarter profit more than doubled from the prior quarter, boosted by a rally in global crude prices, higher output and increased demand for motor fuels. Still its shares fell 7.1%, while shares of construction company Aecon Group ended 9.5% lower after it reported quarterly results. (Reporting by Fergal Smith; Additional reporting by Amal S in Bengaluru Editing by Alistair Bell)