CINCINNATI ( TheStreet) -- Kroger's ( KR) earnings report, released today, provides more proof that the supermarket sector is in for a rough second half of the year. The grocery chain cut its full-year guidance on Tuesday after missing analysts' expectations in the second quarter. The news sent shares tumbling 7.6% to $20.49 just after the opening bell Tuesday. During the quarter, the company earned $254.4 million, or 39 cents per share, down from $276.5 million, or 42 cents per share. Analysts expected the company to earn 44 cents a share. Sales slipped 2% to $17.74 billion from $18.09 billion. Kroger cut its full-year earnings guidance to $1.90 to $2 per share from a prior forecast of $2 to $2.05. The company has been viewed by analysts as the best of one of the worst economic sectors. If that is the case, it doesn't bode well for rivals like Safeway ( SWY) or Supervalu ( SVU). Traditional grocers have been struggling to retain customers who are looking to trade down to discounters like Wal-Mart Stores ( WMT), Costco Wholesale ( COST) and BJ's Wholesale ( BJ). -- Reported by Jeanine Poggi in New York Follow TheStreet.com on Twitter and become a fan on Facebook.