Tip burn and early blight, the two most common foliage troubles of the potato in Iowa, are of enough economic importance in the corn belt to be dealt with profitably thru the use of the bordeaux spray. Five seasons of spraying experiments at the Iowa Agricultural Experiment station point to that conclusion. These tests also suggest that under Iowa conditions five applications of bordeaux mixture per season are likely to be most profitable. That number gave an average annual crop increase of 20 bushels of potatoes per acre and an average annual increased profit of $9.62 per acre. Three applications gave an average annual increase of only 10 bushels per acre and an average annual increased profit of only $2.07 per acre, which seemed too little to be profitable. Seven applications gave an average annual increase of 22 bushels per acre in the yield and of $5.96 in profit representing a diminishing net return.