Sirococcus – dieback of Spruce - Sirococcus conigenus
Symptoms / species
Impact / measures
Bending down of young shoots in May (mostly before longitudinal growth is finished); at first, needles in the middle of the shoot discolored greyish; later on, all needles of the shoot pale, then brown and shrivelled; in summer and autumn minute fruiting bodies visible as blackish dots emerging from the bark (hand lens!); in atumn the shoots drop; repeated infestations may cause branching anomalies, loss in increment, as well as dieback of crown parts (associated with additional microfungi); only young plants may totally die from Sirococcus-infection.
Affected tree species
Needle; Stem; Shoot/Twig/Branch;
Occurring on sites with high moisture (fog, mist, high grass, depressions) a well as in rainy years; primary infections from dry galls of spruce gall aphids. Furthermore, spruces on poor sites (nutrient deficiencies) are highly susceptible; the disease can be mistaken for Grey mould or for Spruce cone rust, which may also infect current years shoots, but here the symptoms appear later in the year (length growth nearly terminated), and there is a blackish stain of the bark.
Curative measures Balanced nutrition, avoidance of sites with high and long lasting humidity
yellowing caused by Sirococcus conigenus
Fruiting bodies on very young, dead needles of spruce
Symptoms in autumn: dried twigs with shorted shoots
heavy infestation of a young spruce
Early symptom: needles neat the shoot base discolored