Trehelse i steinfrukt

In the Treehealth-project it is both new knowledge and communication of existing knowledge. All parts in the value chain from the nursery in the Netherlands, via nurseries in Norway importing trees to Norway, plant protection producer to advisors and growers cooperates with researchers in Norway and the Netherlands participate. Bacterial canker (Pseudomonas syringae) is the most important disease in the project. In sweet cherry orchards in Lærdal it was observed bacterial canker on both newly planted trees and in older plantings. It was differing amount of decay, but in some orchards the incidence was high. Newly planted orchards have been followed in 2015-2018 by counting symptoms. Development differed with orchard, cultivar and between trees. It was not possible to give a clear recommendation to the growers which trees that should be discarded at planting. It was less bacterial canker observed in newly planted plum orchards. In older orchards it could be a higher incidence. Isolations of bacteria identified with fatty acid analysis have shown that all isolations from symptomatic tissue was Pseudomonas syringae pv. Syringae (Pss). From trees without symptoms also Pseudomonas syringae pv. morspronorum (Psm) was isolated. Experiments with following bacterial canker symptoms during a storage period was started in the Dutch nursery. It was symptoms on the trees next spring and isolated both Pss and Psm. A new experiment was initiated were trees without symptoms were marked. In spring 2017 it was symptoms on some of them, but not possible to isolate bacteria. In the nursery a wound protection experiment started at heading back in spring 2016. The results showed no difference and the experiment was repeated in 2017, also with no differences, indicating that the bacteria was present in the trees before heading back. In order to gain more knowledge about how fast symptoms of bacterial canker develop, trees were inoculated. It was grafted trees of different cultivars and inoculated with bacteria at time of grafting. No sweet cherry trees started to grow and only 14% of the plum trees. It was isolated Pss from the bud wood and rot in rootstock. Plum trees were inoculated at heading back and after four months an internal rot had developed 2 to 16 cm down. Pss was isolated from the rot. A similar experiment was conducted in 2017 and bacteria was isolated. Spraying experiments in plum against plum pocket showed that spraying with copper had a good effect. Based on three years of experiments an earlier spraying than now is recommended. Effect of copper applications in sweet cherry against bacterial canker might be difficult to document although the symptoms are diverse and varying from tree to tree. A molecular method for quantification of leaf populations of Pss is established. The results showed more differences between the samples than between treatments. Further tests was promising, but it is still unclear if the method is suitable. Phytophthora incidence in small streams and water from ditches has been investigated in fruit orchards and there have been findings of the pathogen, but low incidence of diseased trees.

Eit auka fokus på sjukdomar på steinfrukttre har ført til at fruktdyrkarar har sett meir krav til trea ved mottak og dei har byrja å kjøpa tre frå andre leverandørar.

Dyrking av steinfrukt (plomme og søtkirsebær) er viktig for Norsk landbruksrådgiving på Vestlandet. Medlemer i NLR Sogn og Fjordane og Norsk fruktrådgiving Hardanger driv meir enn 70% av steinfruktarealet i Noreg. I regionen er det ein klår strategi å auka volumet av begge steinfruktartane med mellom 50 og 100%. Det kan ikkje skje utan at trea er friske. Gjennom eit forprosjekt finansiert av RFFVEST i 2013 vart det avdekka at 1-20% av trea går ut dei første åra etter planting og at det i alle ledd i verdikjeda er eit stort potensiale for å handtera trea betre for å redusera risiko for sjukdomsutvikling. Det manglar kunnskap om biologien til viktige sjukdomar, korleis dei skal handterast optimalt og korleis dyrkingstekniske tiltak påverkar trehelse og sjukdomsutvikling. I prosjektet TreHelse skal det byggjast kunnskap og kommuniserast eksisterande kunnskap. Alle ledda i verdikjeda frå planteskulen i Nederland, via planteskulane som importerer tre til Noreg, produsent av plantevernmiddel til rådgivarar og fruktdyrkarar vil samarbeida med forskingsinstitusjonar i Noreg og Nederland. Dette er første gong alle desse partane i eksportør- og importørlandet samarbeider om ein strategi for sjukdomsfritt plantemateriale. Hovudmålet i prosjektet TreHelse er å auka utbytet i steinfruktdyrking. Tiltak tilrådd på bakgrunn av ny kunnskap og samanfatting av eksisterande kunnskap skal redusera risikoen for utvikling av sjukdomar på trea etter planting og totalt sett gje friskare fruktfelt med større avlingspotensiale. Gjennom kunnskapsbasert rådgiving skal dyrkarane få grunngjevne og rette råd til rett tid. Det vil heva kunnskapsnivået i alle ledd og sikra høgare avlingar av steinfrukt. TreHelse vil auka verdiskapinga i vestnorsk steinfruktdyrking. Potensialet er høgt, og eit forsiktig estimat på 20% høgare avling vil årleg gje ein auke i førstehandsverdi på minst 10 millionar kr for steinfruktdyrkarane på Vestlandet. Resultat frå prosjektet kjem heile norsk fruktdyrking til gode.