* Q3 sales 1.17 bln eur vs 1.19 bln Reuters poll * Q3 EBITDA 168 mln eur vs 192 mln Reuters poll * Still sees 2013 sales of about 4.5 bln eur, lower EBITDA * Shares indicated 3.1 percent lower (Recasts, adds details on polysilicon business, shares) FRANKFURT, Oct 31 (Reuters) - Wacker Chemie's WCHG.DE third-quarter core earnings plunged by nearly a fifth, hit by low prices for polysilicon, a key material it supplies to the crisis-ridden solar industry. Wacker Chemie - the world's No.2 maker of polysilicon, used in solar cells - said its earnings before interest, tax, depreciation and amortisation (EBITDA) came in at 168 million euros ($231 million) in the third quarter. Analysts had, on average, expected third-quarter EBITDA of 192 million euros. "The prices for solar silicon remain a challenge. They were about one-third lower than a year ago," Chief Executive Rudolf Staudigl said in a statement on Thursday. Wacker kept its outlook for the current year for sales of about 4.5 billion euros and a drop in EBITDA. Through its polysilicon business, which accounted for nearly a third of nine-month core earnings, Wacker depends on the solar industry, where oversupply of cells and modules and falling government support has pushed a large number of sector players into insolvency. Polysilicon prices have plunged to below $20 per kg from a 2008 peak of almost $400, squeezing Wacker Chemie as well as major rivals Hemlock Semiconductor and Norway's Renewable Energy Corp REC.OL , triggering those in the sector to cut jobs or reduce capacity. Sector leader Hemlock Semiconductor, a joint venture between Dow Corning DOWCR.UL and Shin-Etsu Handotai SHNETB.UL , in January announced it would cut 400 jobs. ID:nL2N0AJ949 Wacker Chemie also competes with Mitsubishi Materials 5711.T , as well as Korean OCI Co Ltd 010060.KS and China's GCL-Poly Energy Holdings 3800.HK . ($1 = 0.7262 euros) (Reporting by Christoph Steitz; Editing by Victoria Bryan) ((christoph.steitz@thomsonreuters.com)(+49 69 7565 1269)(Reuters Messaging: christoph.steitz.thomsonreuters.com@reuters.net)) Keywords: WACKERCHEMIE RESULTS/