Compass penetrates the plant surface but does not significantly move through the plants vascular system. This allows the fungicide to bind very tightly to the surface of the plant and is therefore very resistant to weather. No longer is morning dew your enemy as dew not only aids Compass' redistribution by spreading and penetration, but also by additional redistribution in the vapor phase. Excellent control of blackspot with 14-21 day spray intervals. Very inexpensive when you consider the usage rate of 1/4 to 1/2 teaspoons per gallon. Package is 16 oz. Shipping Free to Lower 48 States.