2022 CTRE: Rhizoctonia butinii on spruce Christmas trees

Rhizoctonia spp. are soilborne fungi that may attack both woody and herbaceous plants, among them conifer species. In Norway, a Rhizoctonia sp. used to be an aggressive pathogen on Norway spruce (Picea abies) seedlings in forest nurseries (Roll-Hansen & Roll-Hansen 1968), a problem that ceased when the production was shifted from bareroot to plug plants.

However, in Denmark serious attacks by Rhizoctonia have recently been observed in Norway spruce Christmas trees in western Jutland, Denmark. Sequencing (ITS rDNA) revealed that the damage was caused by Rhizoctonia butinii. This fungus has also been reported on white spruce (P. glauca) in Slovenia (Hauptman & Piškur 2013) and on several conifers in the USA (Chastagner & LeBouldus 2018).

A laboratory inoculation test with R. butinii on Norway spruce seedlings confirmed the aggressiveness. In an ongoing trial in a growth chamber at NIBIO, soil from beneath heavily infected Danish Christmas trees has been used for both Norway spruce seed germination and as growth medium for seedlings obtained from a Norwegian forest nursery.

Chastagner, G.A. & LeBouldus, J. 2018. Web blight. Compendium of conifer diseases, second edition, APS press, Minnesota, USA. P 128-130.

Hauptman, T. & Piškur, B. 2013. A new record of Rhizoctonia butinii associated with Picea glauca ‘Conica’ in Slovenia. Forest pathology 46(3):259-263.

Roll-Hansen, F. & Roll-Hansen, H. 1968. A species of Rhizoctonia DC. ex FR. damaging spruce plants in nurseries in southern Norway. Meddel. fra Det Norske Skogf. 82:421-440.