Et krafttak mot frukttrekreft

The project ?KreftKamp? (canker-fight) has research activities in Norway, Germany and Finland with four parts; 1: spore release and infections, 2: cultivar responses on infections, 3: improved treatments; and 4: dissemination. 1: Spore dispersal patterns for Neonectria ditissima are investigated by monitoring the development of spore structures and continuous spore trapping in all three countries. There was a clear effect of the weather during the growing season growing season on the development of perithecia and release of ascospores. In Northern Germany, the first ripe perithecia with spores oozing out were observed in mid-October 2017, while in subsequent years it was later. In Germany a first peak of ascospore discharge occurred in December and January, and a second, larger peak in spring. After that the perithecia disappeared in Germany. In contrast, in Norway and Finland mature perithecia were found all year round. Trap catch data in Norway confirm this. Climatic conditions in the locations are different. The number of days with precipitation during the four observations years were about similar in Finland, Germany and eastern Norway, but there were 40 more days with precipitation in western Norway. Days with mean temperatures between 10 and 20°C, ideal for fungal development, numbered 124 per year in Finland, 44 more in Germany, and Norway in between. It seems that temperature is important for development of spore structures after the infection has become established. 2: Cultivar differences are assessed by inoculation of cut shoots inside in spring and autumn, and in 2020 outside. The development on green shoots on the trees was so fast that no differences between cultivars could be observed. On cut shoots observations of different characters gave fewer differences between cultivars than expected. Trees of different cultivars for assessment of natural infections were planted spring 2018 in two sites in Northern Germany and two in Southern Norway. After three growing seasons 3 % of the trees in Norway had developed canker, and in Germany 1-10 cankers per tree on average. In Norway the infection was higher on cv. Santana, but due to nursery infections. There were no differences between cultivars in infections initiated after planting in Norway. The experiment with natural infections in Germany is still ongoing Leaf fall period and phenological development in spring were assessed in selected cultivars of apple and crabapple in four locations in Southern Norway. Cultivar Julyred started the leaf fall as early as the crab apple cultivars, Summerred was the earliest of the main cultivars, while Aroma was the latest. The mean length of leaf fall period was 30 days. ? 3: Spraying experiments with copper-based products and other chemicals with effect on European canker are ongoing in Germany. German experiments with spraying in the leaf fall period has shown that the copper dose could be reduced without higher risk of infections. The development time from infections in leaf fall period until the onset of visible cankers is shorter in Germany than in Norway and it is easier to relate infections to spraying treatments. Spraying experiments with effects on fruit infections in Norway have not shown differences in fruit rot after storage or incidence of blossom end rot due to N. ditissima. It can be concluded that fruit infections of Neonectria are of minor importance in Norway. Infections on newly planted trees have been assessed in Norway. The incidence of European canker was low in the year of planting. In the following years it increased, whereby particularly high canker incidences occurred on the rootstock B9. The most commonly observed canker on imported trees was on the main trunk in branch angles. Cankers in wounds from support systems and wires were commonly found on both the main trunk and on side branches in orchards in the years after planting. Specifically made or commercial trees were inoculated in spring and summer in 2019. In mean of 10 cultivars 10% of the trees inoculated in heading back wounds before growth start, and 25% of trees inoculated in wounds after manipulating of branch angles in season developed canker. Trees inoculated at planting in pruning cuts or wounds after bending side branches developed canker on 70 and 97% of the trees. 4: The knowledge network is between fruit growers, importers of apple trees, The Elite plant station, Nordox, advisors and researchers. So far this has involved visits of nurseries in the Netherlands and Belgium, grower plots in Norway and Finland (mainland and Åland), Northern Germany and planning meetings. In addition a network about Neonectria both in horticulture and forestry has had a meeting with field visits in Sweden and Denmark. In November 2020 both advisors and researchers participated in a webinar arranged of an international canker working group.

Den spesifikke kunnskapen oppnådd i prosjektet har dokumentert at for så klimatilpassa sykdommer som frukttrekreft er det avgjørende å gjøre undersøkelser i ulike klima. Disse forskjellene har bidratt til en dypere forståelse av soppen sin biologi og klimaforskjeller som vil bli utnyttet videre i det internasjonale samarbeidet. Fokus på tidlig innsats og målrettede tiltak mot frukttrekreft antas å gi langsiktige virkninger på helsetilstand og avlingsnivå. En effekt av det er mer realisme i å nå de politiske målene om høyere andel norskprodusert frukt og grønt på norsk marked. Høyere avlingsnivå og bedre effektivitet i eplehager vil gi bedre produsentøkonomi. En effekt av det er bedre økonomisk grunnlag for bosetning og landbruk i hele landet og grunnlag for å sikre rekruttering til fruktnæringen.

Prosjektsamvirket Oslofjorden frukt og bær har i sitt mandat å fremme forskning som har relevans og høy nytteverdi for å bedre vilkårene for frukt- og bærdyrking og produsentøkonomien. I epledyrking i det nordvestre Europa er frukttrekreft en av de mest alvorlige sjukdommene. Våre dyrkere prioriteter en kamp mot frukttrekreft som det aller viktigste å ta fatt i. De ønsker forskning som kan minimere dette problemet. Vi søker derfor prosjektet KreftKamp som gjennom forskningsarbeid i Norge, Tyskland, Danmark og Finland vil gi ny grunnleggende kunnskap om biologien til Neonectria ditissima, soppen som er årsak til frukttrekreft. Det skal bygges kunnskap om sporespredning og infeksjoner, og det skal arbeides med flere eplesorter, også nye sorter, for å få bedre grunnlag for å forstå biologien og responser på sykdomsangrep. Denne kunnskapen sammen med utprøving av nye tiltak og god agronomi vil gi et løft i håndteringen av frukttrekreft. Kunnskapen skal formidles gjennom feltforsøk i våre frukthager, i demonstrasjonsfelt og gjennom erfaringsgrupper og kunnskapsnettverk på tvers av landegrensene i Nord-Europa. Kunnskapsnettverket og erfaringsutvekslingen skal foregå mellom fruktdyrkere, importører av epletrær, den norske eliteplantestasjonen, rådgivere og forskere, med et felles mål: å intensivere kampen mot frukttrekreft basert på et betydelig kunnskapsløft. Vi vil utnytte våre lokalklimatiske fordeler og dyrke epler til det norske markedet på friske trær med høyt avlingspotensiale. KreftKamp vil gi oss og hele den norske og nord-europeiske fruktdyrkingen et nødvendig løft i kampen mot denne alvorlige sykdommen. Vi forventer en økt verdiskaping fra vårt område med minst 10 millioner årlig og fra norsk epledyrking med mer enn 40 millioner årlig.