CHICAGO, April 15 (Reuters) - US corn futures dipped on Thursday, pressured by commercial hedging after spiking above $6 a bushel for the first time since June 2013 during the overnight trading session. Wheat futures were firmer for the third day in a row, rising to their highest since early March, with persistent concerns about dryness in the US Plains cutting into harvest prospects.

Soyabean futures also were firm. Traders said prices need to rise compared to corn to entice US farmers to plant more acres.

Overnight strength in corn triggered some country movement after the market hit targets that farmers had left with grain dealers.

“There was a little bit more farmer selling once corn hit $6, which makes sense,” said Jim Gerlach, president of US broker A/C Trading.

Additionally, a US Agriculture Department report that showed weekly export sales of corn falling below market expectations added pressure to prices for the yellow grain.

At 10:56 a.m. CDT (1556 GMT), CBOT May corn futures were down 3-1/2 cents at $5.90-1/2 after peaking at $6.01-1/2 a bushel. Concerns about production in Brazil kept the declines in check.

“I think its more of a pause than anything else,” Gerlach said. “You could see the US export market light up again real quick.”

CBOT May soyabeans were 8-1/4 cents higher at $14.18-1/4 a bushel and CBOT May soft red winter wheat was up 5 cents at $6.53 a bushel. Dry weather and a cold surge expected next week poses risk of damage to the wheat crop in the southern US Plains. “The dryness in the US spring wheat growing regions is giving rise to concerns about delays to planting,” Commerzbank said in a note. “What is more, a cold snap is looming in the southern US Plains next week, which could damage the wheat plants there.”