* Corn around 8-year highs, supported by tight supplies * Wheat, soybeans at 2013 peak (Updates with closing prices) CHICAGO, April 26 (Reuters) - Chicago corn futures climbed on Monday to their highest since June 2013 as concerns about South American supplies buoyed the market. Strength in corn pulled wheat and soybeans to eight-year highs. Chicago Board of Trade most-active July corn ended limit up at $6.57-1/2 per bushel. July soybeans gained 23-1/4 cents to $15.39-1/4 per bushel after reaching $15.44-3/4 per bushel, their highest since June 2013. Wheat added 27-1/4 cents to $7.39-1/2 per bushel after reaching $7.46 per bushel, its highest since February 2013. Dryness in Brazil threatens developing second-crop corn as late planting has left the crop vulnerable to drought damage. “It’s the start of the dry season,” said Karl Setzer, commodity risk analyst at Agrivisor. “If we don’t get some rain pretty soon, that’s going to be a concern.” Slow planting across the U.S. Midwest due to a cold snap added support, as domestic supplies dwindle. Analysts expect the U.S. Department of Agriculture to report 17% of U.S. corn acres planted as of April 25 in its Monday afternoon report, with 8% of soybeans planted. Corn exports for the week ended April 22 were 1.9 million tonnes, according to the USDA, beating analyst estimates. “We’re out of corn and beans, for the most part, in the U.S. interior,” said Joe Davis, director of commodity sales at Futures International. Soybeans were supported as Argentina considers an increase in grains export taxes to control domestic food prices. Exporters sold 120,000 tonnes of new crop soybeans for delivery to unknown destinations, according to the USDA, although old-crop sales have cooled. Exporters moved 233,911 tonnes of soybeans last week, within analyst expectations. Wheat is supported by frigid weather in the United States and concerns that acres may shift to more profitable corn or soybeans. “We had freeze talk last week, but we’re a month away from seeing real damage, if there is any,” Davis said. Wheat exports beat expectations, with 564,047 tonnes inspected the week ended April 22. (Reporting by Christopher Walljasper; Additional reporting by Naveen Thukral and Michael Hogan; Editing by Peter Cooney)