The historic selloff in Target Corp's stock /zigman2/quotes/207799045/composite TGT -3.40% is casting a pall on the retail sector, as shares of 90 of the S&P 500's /zigman2/quotes/210599714/realtime SPX -2.01% 92 consumer discretionary and staples companies are trading lower. Target's stock was the weakest of the bunch, tumbling 24.7% toward an 18-month low, as well as the biggest one-day plunge since Black Monday (Oct. 19, 1987), after a hugely disappointing earnings report. The SPDR Consumer Staples Select Sector ETF /zigman2/quotes/200697959/composite XLP -1.34% slumped 4.7%, with all 32 components losing ground, while the SPDR Consumer Discretionary Select Sector ETF /zigman2/quotes/200844504/composite XLY -3.99% , of which Target is a component, also dropped 4.7% with 58 of 60 components falling. Among some of the more sympathetic losers, shares of fellow discount retailers Dollar Tree Inc. /zigman2/quotes/203712248/composite DLTR -2.27% tumbled 17.2% and Dollar General Corp. /zigman2/quotes/200691429/composite DG -1.29% slid 12.2%, while membership-based warehouse retailer Costco Wholesale Corp /zigman2/quotes/201191698/composite COST -2.73% sank 11.6%. Drug store chain and health care services company Walgreens Boots Alliance Inc.'s stock /zigman2/quotes/203410933/composite WBA -2.92% dropped 6.6%, and was the Dow Jones Industrial Average's /zigman2/quotes/210598065/realtime DJIA -1.56% biggest decliner. Walmart Inc.'s stock /zigman2/quotes/207374728/composite WMT -1.41% slumped 5.9%, after tumbling 11.4% on Tuesday on the back of disappointing earnings. The two retail gainers were shares of discount retailers TJX Companies Inc. /zigman2/quotes/203136811/composite TJX -3.90% , which rallied 9.1% after an earnings beat, and Ross Stores Inc. /zigman2/quotes/202639496/composite ROST -4.66% , which tacked on 2.6%.