The members of the NKJ-SNS network project “Neonectria cankers on trees” has gathered for a second meeting. The meeting took place in two participating countries, Sweden (hosted by SLU in Alnarp) and Denmark (hosted by KU at the arboretum in Hornsholm, Denmark).
A brief update on the status of the ongoing research projects in the participating countries as well as on the significantly improved epidemiological situation in apple orchards in Åland was accompanied by a fruitful discussion and knowledge exchange in the network “Neonectria cankers on trees – meeting of changed climatic conditions and increased problems in Scandinavian horticulture and forest production by interdisciplinary networking”.
Since the network is dedicated to the three Neonectriaspp; N. ditissimaon broad leaf trees (especially fruit trees) and N. neomacrosporaand N. fuckelianaon fir (Abies spp.) and spruce (Picea spp.), respectively, the meeting included on-siteexperience of infections on both, horticultural and forest crops.
The participants visited a commercial apple orchard where they could observe damages caused by N. ditissima in a range of apple cultivars differing in their levels of resistance. The observations and discussions were dedicated to the diversity of the symptoms as well as to the diversity of the defence reactions among cultivars. The attention was also drawn to the differences in the severity of damages related to differences in growing conditions within the same orchard as well as to the differences in the age of the trees. The participants stressed on the importance of good orchard hygiene for the improvement of the epidemiological situation in the apple orchards.
In the Arboretum in Hørsholm the focus was on symptoms of N. neomacrospora on different fir species. Abies lasiocarpa and A. concolor show severe infection, whereas traditional forest tree species such as A. alba and A. grandis are less affected. Symptoms of N. fuckeliana on spruce and N. ditissima on broadleaves have not been observed in the Arboretum, and only a few cases have been reported from Danish forests, however no systematic surveys have been carried out. An important discussion was to which degree aphids on needles, shoots and bark facilitate the entry of these pathogens in the hosts.
During the excursion in the Arboretum we looked at a spore sampler experiment and discussed whether this method could be used for other Neonectria species than N. ditissima, since several participants had experienced difficulties with obtaining spores.
An important task of the network is to bring all the collected information on biology, epidemiology and control of the three pathogens, including better utilization of the intrinsic host resistance by combining of breeding resistant genotypes with improved practices to the scientific community though a review paper. The participants agreed on the content and structure of the paper. The important knowledge exchange between the horticulture and forestry as well as a positive and open atmosphere within the group indicate good prospects for further collaborations and join projects.