Reuters March 17, 2012 (BOGOTA) - Colombia's coffee growers' federation on Saturday urged the central bank to stop interest rate increases that are spurring currency appreciation and reducing earnings of coffee exporters as they struggle with slumping production. "Colombian (coffee) exporters have been hard hit by the appreciation of our currency and the weakening of the dollar," said Luis Genaro Munoz, head of the coffee federation, during an event in the province of Huila, which recently overtook Antioquia to become Colombia's top coffee-producing region. "We are sure that government representatives in the central bank received the instructions to revise the effectiveness" of raising rates, he added during the inauguration of a mill with capacity to process 400,000 60-kg bags. The Colombian peso has appreciated 9.35 percent so far this year and 6.7 percent in the last 12 months driven partly by the strong foreign direct inves...