Rhizosphaera Needle Cast
Scientific Name:
Rhizosphaera kalkhoffi
Rhizosphaera needle cast is a foliage disease of spruce trees. It causes significant damage to trees
growing outside of their native range. Older, inner needles show symptoms first. As the disease
progresses, newer needles will exhibit symptoms. Infected needles first appear mottled or speckled with
dull yellowish blotches. Later, the needles turn brown to purplish brown. The needles are dropped (cast)
anywhere from 3 –15 months after infection depending on the variety of spruce infected. Branches
begin dying if they are defoliated in 3-4 consecutive years. Larger trees are rarely killed, however they
may become so disfigured that they lose all of their ornamental value.






Attacks: Colorado spruce, white and black hills spruce
What you will see:
- Thin trees with lower branch dieback
- Excessive thinning/ dropping of older needles
- Black dots in the stomata on the underside of the
needles
- Yellow and purple/brown needles
Life cycle:
- Needles are infected with the pathogen in spring during
wet weather
- New needles are susceptible to disease - all year long
- Fallen needles produce spores that re-infect healthy
needles
- Wet and/or humid conditions promote disease
Management of Rhizosphaera Needle Cast
Cultural practices:
- Reduce moisture adjacent to tree
- Move sprinkler heads
- Do not water foliage
- Increase air flow through canopy
- Prune out infected tissue
- Remove fallen needles
- Do not plant Colorado spruce
Chemical Treatments:
- Treat foliage with fungicide to prevent infection
- Make sure treated trees will not continue to be in contact
with moisture
- After treatment needles may continue to change color
and fall off, since infection occurred prior to treatment.