First report of Diplodia tip blight on Scots pine in Finland

Abstract

Diplodia sapinea (Fr.) Fuckel causes shoot blight on Scots pine (Pinus sylvestris L.). This fungus has been discovered in Finland as a saprophyte in 2015 on Scots pine cones. The endophytic mode of this fungus was later discovered in healthy Scots pine twigs. In 2021 the disease, Diplodia tip blight was observed on Scots pine in Finland. Currently, the disease symptoms are poorly identified so the role of D. sapinea in disease outbreaks in Finland are easily overlooked. The identification of the fungi is challenging in field conditions and requires targeted identification in laboratory. In this research note I report the first Diplodia tip blight outbreaks observed in Finland, the typical disease symptoms, and methodology for the species identification. Samples were collected from symptomatic trees based on observations made by the citizens. Diplodia sapinea was isolated from defoliated and surface sterilized twigs. The species identification by morphological characters was further confirmed with sequencing of ITS region of rDNA and with species-specific primers. A pathogenicity test confirmed that D. sapinea was the disease agent causing shoot blight. This is the first report of Diplodia tip blight on Scots pine in Finland.

First report of Diplodia sapinea causing Diplodia tip blight on Juniperus communis subsp. communis in Finland

“…The disease agent, D. sapinea, was previously found in Finland on Scots pine cones collected from the ground (Müller et al, 2019) and from healthy Scots pine twigs (Terhonen et al, 2021). Besides J. communis reported here, D. sapinea has been recently demonstrated to cause Diplodia tip blight in Finland on Scots pine (Terhonen, 2022).…”

“…, 2021). Besides J. communis reported here, D. sapinea has been recently demonstrated to cause Diplodia tip blight in Finland on Scots pine (Terhonen, 2022). Diplodia sapinea can be endophytic and may turn pathogenic in drought‐stressed trees (Blumenstein et al.…”

“…communis ) in coastal Finland. The sites were previously confirmed to contain Scots pine ( Pinus sylvestris ) trees with Diplodia tip blight disease, caused by Diplodia sapinea (Terhonen, 2022) (Fig. 1).…”