Utskrift
Dyrking av juletrær er en intensiv helårsproduksjon som har økt mye i omfang og profesjonalitet de siste par tiårene. NIBIO og forløper-instituttene har i denne perioden drevet forskning på mange av de utfordringene juletrenæringen har stått ovenfor.
Inger Sundheim Fløistad
Seniorforsker
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Divisjon for skog og utmark
(+47) 452 27 021 inger.floistad@nibio.no Kontorsted: Ås - Bygg H8
Målet har hele tiden vært å bistå bransjen med kunnskap som gir økt effektivitet i produksjonen og bedre kvalitet og holdbarhet på juletrærne. Derfor samarbeider vi tett med dyrkernes medlemsorganisasjon Norsk Juletre (se lenke til venstre).
Prosjektutvikling sammen med juletredyrkernes veiledningstjeneste sikrer medvirkning i prosjektene og relevante problemstillinger.
NIBIOs forskning på juletreområdet holder et høyt nivå også i et internasjonalt perspektiv. Den internasjonale forskerorganisasjonen IUFRO har et eget nettverk hvor juletreforskere og rådgivere møtes hvert annet år for å utveksle oppdatert kunnskap. Erfaringsutvekslingen gjennom forskerkollegaer i Europa og USA har bidratt til å løfte produksjonen i Norge.
Tradisjonelt ble vanlig gran (Picea abies) og noe furu (Pinus sylvestris) valgt som juletre fra foryngelsesfelt i skogen.
Edelgran (Abies) har lenge vært dyrket i stor målestokk som juletre i Danmark, og også eksportert til Norge. Etter hvert som dyrkingen ble satt i system her i landet, ble det interessant å prøve ut nye arter.
Arter fra slekten edelgran har nålefeste som gjør at nålene sitter lenger på kvisten enn på arter fra granslekta. Nordmannsedelgran (A. nordmanniana) og fjelledelgran (A. lasiocarpa) er i dag de to mest dyrkede juletre-artene i Norge, i tillegg dyrkes blant annet sibiredelgran (A. sibirica), fraseredelgran (A. fraseri) og koreaedelgran (A. koreana).
I granslekta er det også flere arter som dyrkes som juletre i tillegg vår vanlige gran, både serbergran (Picea omorika) og engelmannsgran (P. engelmanni), regnes å ha noe bedre nålefasthet enn vanlig gran, selv om holdbarheten ikke er like lang som edelgranene.
Også innen samme art varierer juletreets egenskaper etter hvor frøene er sanket. Det har vært testet mye ulikt frømateriale for å finne frem til hvilke trearter og frøkilder som egner seg for norske dyrkingsforhold.
I dag bygger Skogfrøverket videre på denne kunnskapen og har etablert egne felt for frøproduksjon av utvalgte frøkilder (lenke til Skogfrøverket under bildet til venstre).
Det er som nevnt en del variasjon mellom ulike arter på hvor mye juletrærne drysser. Heldigvis er det også en del forbrukeren selv kan gjøre for å bedre holdbarheten til trærne.
Svært mange av de dyrkingstekniske tiltakene som gjennomføres i dag, er gode også når det gjelder å forebygge skadegjørere i juletrefelt. Dette er i tråd med prinsippene for integrert plantevern (IPV) og NIBIO har laget IPV veiledere også for juletre (se lenke til venstre).
Friske småplanter sikrer god etablering og man unngår å bringe inn nye skadegjørere. Drenering gir også bedre etablering, noe som gjør juletrærne mer konkurransesterke mot ugras og reduserer risikoen for angrep av jordboende skadegjørere som Phytophthora.
Vegetasjon rundt juletrefeltene kan ha viktig betydning som le, og være et reservoar for nyttedyr og pollinerende insekter, men man bør unngå bartrær som kantvegetasjon da de kan være vertplanter for både skadedyr og sjukdomsorganismer.
Ugras tett på juletrærne fører til sterk konkurranse om vann og næring og gir redusert tilvekst og kvalitet. Visse ugrasarter kan også gi økte problemer med sykdommer i trærne. Det er derfor av stor verdi for produsentene å holde ugraset nede gjennom hele produksjonstiden.
En rekke sjukdommer har blitt kartlagt gjennom prosjekter i NIBIO. Noen av disse er nye som skadegjørere i Norge. For å kunne forebygge sjukdommer er det viktig å kjenne tidlige symptomer og spredningsmønster. På samme måte har identifikasjon av skadedyr betydning for å kunne forebygge og sette inn tiltak ved behov.
For å hjelpe med identifikasjon av skader, har NIBIO laget boka "Skader i juletrefelt –biotiske og abiotiske årsaker" som selges av Skogkurs (se lenke til venstre).
Identification of stocktype attributes that speed up field establishment has potential to reduce rotation time of Christmas tree productions. Such morphological and physiological attributes can be targeted in the nursery production. This study tested the effects of container type and nursery seedling density on stocktype attributes at planting and the effects of these on field performance over two years in Abies lasiocarpa and A. nordmanniana Christmas tree stock. Nursery conditions had a considerable impact on seedling attributes at planting. Although sets of these correlated stocktype attributes contributed to forecast field performance, the predictive power was low. No simple relationships were found between plant biomass, stem diameter or height at planting and biomass at final harvest in either of the two species under the range of stocktype variation and field conditions tested. Contrary, stem diameter and stem height at planting explained some of the responses in stem diameter and height after two years in the field. Thus, any target seedling approach would have to be based on a combined set of stocktype attributes exploring more productive stocktypes. The differences observed between stocktypes were largely due to size differences and ontogenetic drift, and stocktypes converged towards a similar field phenotype over time.
In integrated pest management (IPM), the goal is to keep the impact of damaging agents below a threshold level with reduced pesticide use. The present review is focusing on IPM of fungal diseases and Phytophthora root rot in Norwegian Christmas tree plantations. Healthy transplants are of vital importance to give the production a good establishment. Sanitation of diseased material and weeds is also very important in IPM. Management strategies will vary with the disease-causing agent in question, therefore, correct identification is necessary. The major pathogens are within the kingdom’s Fungi (e.g. Neonectria neomacrospora) and Chromista (e.g. Phytophthora spp.). They depend on relatively high humidity or free moisture to spread and infect. Any factors diminishing the duration of wet conditions will, therefore, reduce the disease pressure. Efficient weed management in Christmas tree fields will increase air circulation and thereby ensure a quicker drying after precipitation. Furthermore, certain weed species are host plants for rust fungi on Christmas trees, and thus, removal of the alternate host is a highly relevant control strategy. In Norway, fungicide use in Christmas trees is limited and only recommended during the short period from bud break to fully elongated shoots, generally the most vulnerable period concerning fungal attacks.
Norway spruce (Picea abies) is a widely used Christmas tree species in the Nordic countries. Postharvest needle retention is an important characteristic for Christmas trees and compared to many fir (Abies) species, Norway spruce has poor postharvest needle retention. This trait is one of the most important qualities in choice of natural versus plastic trees. In this study, current year shoots were cut from 30 Norway spruce seedlot sources, including the most widely used Norwegian Christmas tree provenances, and tested to identify genetic variation in postharvest needle retention. Current year shoots were collected from one field in November and December 2018, and from three fields in October, November and December 2019. The current year shoots were displayed indoors under controlled conditions and allowed to dry. Differences in postharvest needle retention were seen between seedlots, harvesting dates and locations. Our study indicates possibilities of selecting for improved postharvest needle retention in Norway spruce seed sources. Furthermore, postharvest needle retention should be considered as one characteristic to add in the ongoing Norway spruce Christmas tree breeding program.
Subalpine fir (Abies lasiocarpa (Hooker) Nuttall), which is native to western North America, is of considerable interest for Christmas tree production in northern Europe. Seedlings are usually grown from seeds under combined nursery greenhouse/outdoors conditions, but commonly show early growth cessation in the nursery, resulting in small plants for field transplanting. This increases the production time and makes the seedlings vulnerable to stressors at the planting site. Day extension with far-red (FR) light was shown to enhance elongation and delay bud set in seedlings of some woody species, but such information is limited for Abies. Here, we investigated the effects of day extension with FR, red (R), different R:FR-ratios or blue (B) light from light emitting diodes on subalpine fir seedlings grown at different temperatures. Day extension with FR or combined R-FR light, in contrast to R or B light, increased shoot elongation significantly as compared to short days without day extension, often with more growth at 18 ◦C than 24 ◦C. The FR treatments delayed terminal bud development, although bud set was not completely prevented. These results demonstrate that larger seedlings of subalpine fir seedlings for Christmas tree production can be obtained by employing day extension with FR or combined R:FR light, preferably under cool temperature.
Phytophthora cryptogea, P. gonapodyides, P. lacustris, P. megasperma, P. plurivora, P. taxon paludosa and an unknown Phytophthora species were isolated from waterways and soil samples in Christmas tree fields in southern Sweden. In addition, P. megasperma was isolated from a diseased Norway spruce (Picea abies) plant from one of the fields in Svalöv. Inoculation tests were sequentially carried out with one isolate from each of the three species P. cryptogea, P. megasperma, and P. plurivora, all known pathogens on conifers. The same three isolates were used to study a few morphological features to confirm the identification, and temperature-growth relationships were carried out to see how well the organisms fit into Swedish climatic conditions. Seedlings of Norway spruce and Nordmann fir (Abies nordmanniana) were inoculated in the roots and the stems. None of the isolates caused extensive root rot under the experimental conditions, but all three species could be re-isolated from both Norway spruce and Nordmann fir. Phytophthora root rot is currently of minor concern for Christmas tree growers in Sweden. However, the Phytophthora isolations from soil and water indicate the presence of this damaging agent, which may lead to future problems.
The fungus Neonectria fuckeliana has become an increasing problem on Norway spruce (Picea abies) in the Nordic countries during recent years. Canker wounds caused by the pathogen reduce timber quality and top-dieback is a problem for the Christmas tree industry. In this study, four inoculation trials were conducted to examine the ability of N. fuckeliana to cause disease on young Norway spruce plants and determine how different wound types would affect the occurrence and severity of the disease. Symptom development after 8–11 months was mainly mild and lesion lengths under bark were generally minor. However, N. fuckeliana could still be reisolated and/or molecularly detected. Slow disease development is in line with older studies describing N. fuckeliana as a weak pathogen. However, the results do not explain the serious increased damage by N. fuckeliana registered in Nordic forests and Christmas tree plantations. Potential management implications, such as shearing Christmas trees during periods of low inoculum pressure, cleaning secateurs between trees, and removal and burning of diseased branches and trees to avoid inoculum transfer and to keep disease pressure low, are based on experiments presented here and experiences with related pathogens.
The Christmas tree industry in Norway is increasing and Abies lasiocarpa is, together with Abies nordmanniana, the most common exotic species for Christmas tree production. A. lasiocarpa today constitutes ca. 50% of the fir sold in Norway, and there is high demand for sufficient supply of high-quality seed and knowledge of seed sources with a potential for high Christmas tree quality. Two experimental plots were established to identify seed sources with potentially high survival and satisfactory Christmas tree quality. The high variation in traits on the two sites indicates promising possibilities for further selection of A. lasiocarpa clones for growing Christmas trees in Norway. Selection for late bud break to avoid spring frost is important. Pathogens were not found in any of the studied trials, but are an important factor to consider when selecting seed sources for Christmas trees. Due to the early bud break of this species, it is also of high importance to choose planting sites with minimal risks for spring frost. Good localities are slopes where the frost drains away during cold nights. In eastern Norway, A. lasiocarpa should be used with care in districts and sites where spring frost is commonly occurring.
Det er ikke registrert sammendrag
Ten exotic Abies species were tested in two field trials, where the aim was to find suitable species and provenances for Christmas tree production in coastal and fjord areas in Norway. The material included 14 provenances of Abies nordmanniana, 3 provenances of Abies bornmuelleriana, 3 provenances of Abies koreana, 2 provenances of Abies amabilis, and 1 provenance each of Abies equi-trojani, Abies alba, Abies procera, Abies homolepis, Abies nephrolepis, and Abies forrestii. Field trials were established at Gulen in Sogn og Fjordane County and at Verdal in Nord-Trøndelag County. Christmas tree classification was done seven and eight growing seasons after establishment. The Christmas tree yield was higher in Gulen (64%) than in Verdal (45%), which is situated further north. Also, the survival and the height growth were higher in Gulen than in Verdal. A more humid climate and a longer growth season in Gulen may explain some of the differences. Of the 10 species, A. nordmanniana, A. homolepis, and A. bornmuelleriana produced the highest Christmas tree yield at Gulen, while A. homolepis and A. koreana had the highest yield at Verdal. Due to early bud burst, A. equi-trojani and A. bornmuelleriana are only suited for Christmas tree growing in the best climatic areas.
Det er ikke registrert sammendrag
