Anticipate the future needs of the mature tree and consider whether the site has the potential of supplying the water requirements of a 50-60' tall specimen. Prune infected branches. Rhizosphaera needlecast Year-old needles turn lavender in color and have tiny black fungal fruiting structures in rows on either side of the midvein on the underside of the needle. Large bare areas develop on the tree as needles fall. Blue and Engelmann spruce are highly susceptible.
White spruce are somewhat susceptible.
Norway spruce are relatively resistant. Rhizosphaera Space trees and provide good weed control to insure free air circulation around the tree. Some locations have an additional infection period in September and October. Needle Rust Year-old needles are cast after turning rust colored in the spring. Blue spruce is very susceptible.