In early summer 1 – several yellow cross-bands on the needles; from August on spore cushions in the bands (aecidia), which later on release high numbers of orange-yellow (aecidio-)spores. The cushions are surrounded by whitish sheets. Needles drop.
Affected tree species
Periodically common at the upper tree line, more rarely in lowlands, only, where spruces and Rhododendron species are growing in close vicinity, since the spread of the fungus requires both hosts. The number of spores developing in Rhododendron-leaves in spring is probably the triggering factor for outbreaks on spruce, since these spores infect new needles following especially mild winters. Up to now even repeated intense attacks didn't cause loss of spruces, with the exception of very young plants. Further information (in German) see Gehölzkrankheiten in Wort und Bild (TUM Weihenstephan)
Curative measures Measures are not known, any eradication of the main host (Rhododendron) is impossible due to nature protection laws in the alpine areas.
Symptoms on Picea abies, intense infestation
Needle of Picea abies with aecidia
Symptoms on Picea abies, moderate infestation
Spruce needle rust: uredo-form on leaves and shoots of Rhododendron