Spruce needle rust, caused by several species of the fungus Chrysomyxa, is a common disease on black, white and Colorado blue spruce in Minnesota, and occasionally Norway spruce. Spruce needle rust requires an alternate host in order to complete its life cycle. In Minnesota, the most important alternate host is Labrador tea, but other swamp heath plants such as leather leaf also serve as alternate hosts.

The alternate host produces spores in the spring which are wind blown to new growth on spruce trees. White blisters, reproductive structures, are visible on spruce needles in late summer to early fall. These blisters are filled with orange-colored spores that are wind blown to the alternate hosts, completing the life cycle.

Symptoms of spruce needle rust are yellowing of the needles in July and August, formation of white blisters filled with orange spores, and defoliation. In severe infections, up to 75% of the current year's needles may drop off the tree by September.

Spruce are seldom killed by needle rust, although repeated infections will slow tree growth. To increase tree vigor, water during dry periods, mulch, and fertilize when necessary. There are no fungicides registered for control of spruce needle rust. Choose resistant species, such as Norway spruce, whenever possible and avoid planting susceptible spruce near swamps containing Labrador tea and leather leaf. Removal of alternate hosts will reduce infection of spruce trees, but is not usually practical.

P457S
Revised 12/99
Chad Behrendt, Crystal Floyd