Rhizosphera Needle Cast

Rhizosphera Needle Cast, rhizosphera kalkhoffi is a fungal disease that affects the foliage of spruce trees. It is perhaps the most common needle disease affecting spruce trees in Wisconsin.  Trees that are stressed from drought and mechanical factors, such as poor planting practices and improper fertilization tend to be more likely to suffer from Rhizosphaera needle cast.

Affected trees:  Colorado blue spruce, Picea pungens, happen to be highly susceptible to this disease, while white spruce (including Black Hills spruce), P. glauca, is intermediate in susceptibility, and Norway spruce, P. abies, is relatively resistant.

Noticeable Signs

Common signs of rhizosphera tend to show:

  • older, inner, needles show symptoms first, followed by newer growth as the disease progresses.
  • needles will appear modeled with dull yellow blotches, later turning brown.
  • black spots can be seen through a magnified glass in the stomata on the underside of the needles.
  • infected branches will exhibit noticeable signs of branch thinning, especially on the lower canopy and move upward as the disease progresses.
  • needle cast (drop) can happen anywhere from 3-15 months after infection, depending on the species.

Treatment/ Management 

Reduced moisture along with increased airflow through proper pruning will help control the progression Rhizosphera Needle Cast. Proper sanitation of dropped needles can generate a healthier tree.

We suggest a two application fungicidal spray program beginning just after the new growth emerges and the second spray roughly three weeks later.

Informational Packet (PDF)