NEW YORK (Reuters) - U.S. mortgage applications fell last week as interest rates hit their highest in over four years, an industry trade group said on Wednesday. ADVERTISEMENT The Mortgage Bankers Association said its seasonally adjusted index of mortgage application activity for the week ended June 23 decreased 6.7 percent to 529.6 from the previous week's 567.6. Borrowing costs on 30-year fixed-rate mortgages, excluding fees, averaged 6.86 percent, up 0.13 percentage point from the previous week, its highest level since April 12, 2002 when it reached 6.92 percent. The MBA's seasonally adjusted purchase mortgage index fell 6.2 percent to 389.0....