It was therefore planned from the start not merely to demonstrate the possibility of controlling apple insects and diseases but also to determine whether they could be controlled profitably. To accomplish this it was necessary to know: exactly what it cost to spray, what sprayed fruit yielded, and what it was worth in comparison with unsprayed fruit from the same orchards. In every spraying demonstration the time spent in mixing and applying the materials and the quantity of material used were recorded. The cost of labor of men and teams per hour was taken at the orchard owners\u27 estimates and the cost of materials was charged at the prices actually paid by the orchardists. In every orchard a block was set apart for the demonstration spraying, and another block, in every way comparable with the first, was left without spraying as a check on the results of spraying. The exact yields of both marketable and unmarketable fruit from the sprayed and from the unsprayed blocks, or from considerable parts of them, were noted. The net value of the fruit was determined by deducting from the actual prices received by the owners the estimated cost of picking, grading, packing, hauling, etc. The net value, therefore, was what the fruit was worth on the trees