Tenacity of Copper Fungicide Deposits

Copper fungicides are purely protectant in action. They prevent germination of fungal spores and germ tube penetration into the plant. Discrete droplets and "continuous" films of spray liquid dry to form a fungicide deposit on the foliar surface. This initial deposit subsequently becomes the effective deposit when all but the fungicide in direct contact with, and adhering to, the plant surface sloughs off. The effective deposit becomes a residue as fungicide is removed by weathering, metabolic degradation, abrasion and dislodgement by growth movement. The transient deposit may be effective while present (Furmidge 1962; Ebeling, 1963).