Copper sulphate is sprayed in roses for

Copper sulphate is sprayed in roses for Defoliation.
Defoliation is to deprive leaves especially prematurely by the attack of black spot fungus in roses. Thus copper sulphate antifungal is sprayed on the infected plants.
The effect of such a copper sulphate fungicide is preventing fungal infections on healthy plant tissue or the reduction of active fungal infections that can disease or destroy the plant.