Greater Des Moines foreclosure rates increased slightly in April, according to real estate research firm CoreLogic Inc. The rate of foreclosures among outstanding mortgage loans was 2.57 percent, compared with 2.27 percent in April 2010, CoreLogic said. Foreclosure activity in Greater Des Moines remained below the national rate, which was 3.47 percent in  April 2011. The percent of mortgage loans that were 90 days or more delinquent dropped to 4.55 percent in April from 4.9 percent in April 2010, CoreLogic said.