In an effort to thwart the spread of orange rust fungus in the coffee plantation, Heber and I have taken to using a solution of mandarin lemon juice , 1 liter, to 19 liters of water. The first application was last week. This mornings coffee inspection has revealed that the current outbreak of fungus has stopped. The usually bright orange spores have dried and are white powder, indicating that they are dead. It seems that a possible means of fungus control on coffee could be as simple as citric acid at the right concentration. 1: 19 is the formula.