Mostly older needles turn dull green, later on yellow brown and finally are cast. In case of heavy infestation needles often remain attached to the twigs by threads (similar to conifer spinning mites!). In Picea pungens often the distal half of the needle breaks off, leaving the inner half on the twig. The minute black and ball-shaped fruiting bodies emerge from the stomata and appear on the surface as numerous black dots, which carry the wax of the stoma as a white "cap“ on their top.
Affected tree species
Especially Rhizosphaera kalkhoffii is a nearly ubiquitous coloniser of needles of spruce and fir species, which have been weakened by weather-conditions as frost, high precipitation following drought periods or by light or nutrient deficiencies. The species also play a role as primary colonizers of senescent needles. Epidemic occurrence is rare. The symptoms may be mistaken for those by sooty moulds or sooty coatings.
Curative measures Measures at most in nurseries and Christmas tree cultures – avoidance of the weakening factors