New fungal threat identified in Nordic oak forests as climate shifts
Swedish researchers have identified two distinct powdery mildew species attacking young oak trees—with one species appearing in the country for the first time. The finding matters for forestry operations and timber producers across Scandinavia, who rely on oak breeding programs to ensure healthy future harvests as growing conditions change.
Originaltitel: Powdery mildew on oak (Quercus robur and Q. petraea) saplings in Southern Sweden
Abstract Powdery mildew is a common disease of oak ( Quercus spp.) and other broadleaf forests, which have an increasing ecological, social and economic importance in Sweden and the Nordic region. However, the identity of the causal agents infecting young oak saplings has received little attention. The aim of this brief study was to identify the powdery mildew species colonizing sessile oak ( Q. petraea ) and pedunculate oak ( Q. robur ) saplings of different provenances in southern Sweden. Symptomatic leaves were sampled from five provenances of the two oak species at a common garden field trial in the Swedish breeding program. A total of 28 powdery mildew specimens were subjected to molecular identification and phylogenetic analyses. All but one specimen was identified most likely as Erysiphe alphitoides . One specimen collected from Q. petraea was identified as E. quercicola with strong phylogenetic support. These results confirm earlier findings indicating E. alphitoides as the dominant powdery mildew on oak saplings in southern Sweden, and provide the first unambiguous record of E. quercicola on Q. petraea in the country. The findings contribute to a better understanding of powdery mildew diversity on oaks in northern Europe.