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The effect of steam thermotherapy on Botrytis spp. populations in strawberry transplants was evaluated. Tray plants rooted in 0.2 L peat plugs of seasonal flowering cvs. Falco, Sonsation, and Soprano, and everbearing cvs. Favori and Murano were pre-treated with steam at 37 °C for 1 h, followed by 1 h at ambient temperature and air humidity, and then 2 or 4 h steam treatment at 44 °C. Except for one cultivar with a slight reduction in yield, there were no negative effects on plant performance. Compared to untreated transplants, mean incidence of Botrytis on the five cultivars was reduced by 43 and 86% with the 2 and 4 h treatments, respectively. Within cultivars the reduction was significant in 2 and 3 experiments following the 2 and 4 h treatments, respectively. Sclerotia from four different isolates of Botrytis were subjected to treatment including 4 h of steam thermotherapy and subsequently tested for viability. Following 14 days of incubation, 90 to 100% (mean 97%) of treated sclerotia failed to produce mycelial growth compared with untreated sclerotia, which all germinated and produced mycelia. Botrytis isolates recovered from both treated and untreated strawberry transplants were tested for resistance to seven fungicides, including boscalid, fenhexamid, fludioxonil, fluopyram, pyraclostrobin, pyrimethanil and thiophanate-methyl. Multiple fungicide resistance was common; 35.5% of isolates were resistant to fungicides from at least three FRAC groups. Results indicate that steam thermotherapy treatment strongly reduces populations of Botrytis spp., including fungicide-resistant strains, in strawberry transplants with negligible negative impacts on the transplants.

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Control of grey mould, caused by Botrytis spp., is a major challenge in open field strawberry production. Botrytis was isolated from plant parts collected from 19 perennial strawberry fields with suspected fungicide resistance in the Agder region of Norway in 2016. Resistance to boscalid, pyraclostrobin and fenhexamid was high and found in 89.1%, 86.0% and 65.4% of conidia samples, respectively. Multiple fungicide resistance was common; 69.6% of conidia samples exhibited resistance to three or more fungicides. Botrytis group S and B. cinerea sensu stricto isolates were obtained from 19 and 16 fields, respectively. The sdhB, cytb, erg27 and mrr1 genes of a selection of isolates were examined for the presence of mutations known to confer fungicide resistance to boscalid, pyraclostrobin, fenhexamid and pyrimethanil plus fludioxonil, respectively. Allele-specific PCR assays were developed for efficient detection of resistance-conferring mutations in cytb. Among B. cinerea isolates, 84.7%, 86.3% and 61.3% had resistance-conferring mutations in sdhB, cytb and erg27, respectively. A triplet deletion in mrr1, resulting in ΔL497, commonly associated with the multidrug resistance phenotype MDR1h, was detected in 29.2% of Botrytis group S isolates. High frequencies of resistance to several fungicides were also detected in Botrytis from both imported and domestically produced strawberry transplants. Fungicide resistance frequencies were not different among fields grouped by level of grey mould problem assessed by growers, indicating factors other than fungicide resistance contributed to control failure, a fact that has important implications for future management of grey mould.

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In this study, we investigated if a steam treatment program used to produce disease-free strawberry transplants has the potential to also eliminate strawberry mite (Phytonemus pallidus) and two-spotted spider mite (Tetranychus urticae). Crowns of strawberry plants collected in a commercial field, containing young, folded leaves with all life stages of P. pallidus, and strawberry leaf discs on water agar with T. urticae with non-diapausing adult females and eggs from a laboratory rearing, were exposed to warm aerated steam in a steam cabinet in a series of four experimental runs over 2 years. The steam treatments constituted of a 1-h pre-treatment with 37 °C steam followed by a 1-h recovery period at 21–25 °C, and then a main steam treatment at 44 °C for either 2, 4 (both P. pallidus and T. urticae) or 6 h (the more heat tolerant T. urticae only). After steaming, the plant material with P. pallidus or T. urticae were incubated at 21–25 °C until survival was assessed after 1–6 days, depending on the mite species and life-stage. Non-steamed plant material with mites was used as controls. The 4-h treatment killed all P. pallidus eggs, larvae and adults, and the 2-h treatment killed all individuals in all three stages except for one egg in one of the runs. There were no or minor effects of the steam treatments on T. urticae adult and egg survival. Based on these results, the tested steam treatments may be used to eliminate the strawberry mite but not the two-spotted spider mite from strawberry planting material.

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Strawberry powdery mildew, caused by Podosphaera aphanis, can be particularly destructive in glasshouse and plastic tunnel production systems, which generally are constructed of materials that block ultraviolet (UV) solar radiation (about 280 to 400 nm). We compared epidemic progress in replicated plots in open fields and under tunnels constructed of polyethylene, which blocks nearly all solar UV-B, and two formulations of ethylene tetrafluoroethylene (ETFE), one of which contained a UV blocker and another that transmitted nearly 90% of solar UV-B. Disease severity under all plastics was higher than in open-field plots, indicating a generally more favorable environment in containment structures. However, the foliar severity of powdery mildew within the tunnels was inversely related to their UV transmissibility. Among the tunnels tested, incidence of fruit infection was highest under polyethylene and lowest under UV-transmitting ETFE. These effects probably transcend crop, and the blocking of solar UV transmission by glass and certain plastics probably contributes to the widely observed favorability of greenhouse and high-tunnel growing systems for powdery mildew.

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Det ble i 2020 utført forsøk mot soppsjukdommer i grønnsaker, potet, plomme, bringebær og korn. I potet ble det gjort forsøk mot tørråte, i plomme mot plommepung og i bringebær mot rust. I korn ble det testet nye sprøytestrategier mot bladflekksjukdommer i bygg og vårhvete, og i grønnsaker ble det gjort forsøk mot lagringssjukdommer i gulrot og løk. Det er utført et forsøk med biologiske og kjemiske skadedyrmidler mot kålmøll i kinakål og et forsøk med pluggbehandling av kålplanter (hodekål) før utplanting for beskyttelse mot kålflueangrep. Det er også utført forsøk med kjemiske middel mot bringebærbille i bringebær, kirsebærmøll i kirsebær og mot plommevikler i plomme. I tillegg har NIBIO utført forsøk for å vurdere om feromonforvirring kan brukes som planteverntiltak mot eplevikler og sju andre viklerarter i økologisk epleproduksjon.

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Meldugg, forårsaket av soppen Oidium anacardii, er en viktig sykdom ved produksjon av cashewnøtter. I dette arbeidet er det sett på effekten av ‘bio-spray’ (en blanding av utvalgte mikoorganismer og sirup fra casheweple og/eller sukkerrør) mot meldugg og for å finne den optimale konsentrasjonen av middelet mot sykdommen. To forsøk ble gjennomført; i et skygge-hus med småplanter av cashew og på friland i en ordinær planting. Det var fire behandlinger med ulike konsentrasjoner av bio-spray (10%, 15%, 20% and 25%), i tillegg til behandlinger med sirup (uten mikroorganismer tilsatt) i 5% konsentrasjon eller standard fungicider. Et kontroll-ledd var helt ubehandlet, mens et annet var behandlet med vann. I skyggehuset ble plantene inokulert med smitte fra andre planter, mens forsøkene på friland ble lagt i et felt som tidligere hadde hatt mye meldugg. I skyggehuset ble det foretatt to behandlinger med 15 dagers mellomrom bortsett fra fungicid som ble brukt en gang. På friland ble det foretatt fem behandlinger med enten bio-spray, sirup eller vann med 15 dagers mellomrom, mens standard fungicidbehandling ble utført tre ganger med 21 dagers mellomrom. Prosent blad med angrep og angrepsgrad ble registrert i skyggehuset. På friland ble i tillegg fenologisk stadium og avlingseffekter undersøkt. I skyggehuset ble det lite angrep av meldugg, mens det var betydelig angrep på friland. Det såkalte arealet under sykdomskurven (AUDPC) viste at de ulike konsentrasjonene av bio-spray ikke reduserte meldugg sammenlignet med kontroll-leddene. Det var noe bedre effekt av 15% konsentrasjon sammenlignet med 25%. Behandling med fungicider var signifikant bedre enn de andre behandlingene og var det eneste forsøksleddet som gav god kontroll av meldugg.

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We designed and deployed an apparatus to apply UV light for suppression of powdery mildew in open field production of strawberry. The unit was evaluated in a commercial production field for one season, and for two additional seasons in open field research plots at the University of Florida Gulf Coast Research and Education Center. The apparatus contained two 180-cm-long hemicylindrical arrays of twenty 55-W low-pressure discharge UV-C lamps (operated at 30 W; peak wavelength = 254 nm) backed by polished aluminum reflectors covering two adjacent beds of the strawberry planting. The lamp arrays were suspended within a steel carriage that was tractor-drawn through the planting at 2.3, 4.6, and 5.6 km h−1. Nighttime applications of UV-C at doses ranging from 65 to 170 J⋅m−2 either once or twice weekly provided suppression of foliar and fruit disease that was consistently equal to or better than that provided by a commercial calendar-based fungicide spray program.

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I denne rapporten presenteres resultater fra biologisk veiledningsprøving av soppmidler i bygg, hvete, setteløk, gulrot og solbær. Det er også presentert et forsøk med skadedyrmidler mot kålmøll i kinakål. I tillegg er det rapportert et forsøk mot bringebærbarkgallmygg og ferskenbladlus, et forsøk med kairomonfeller mot skadedyr i eple, og et forsøk med vekstregulering av juletrær.

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In a number of pathosystems involving the powdery mildews (Erysiphales), plant stress is associated with decreased disease susceptibility and is detrimental to pathogen growth and reproduction. However, in strawberry, anecdotal observations associate severe powdery mildew (Podosphaera aphanis) with water stress. In a 2017 survey of 42 strawberry growers in Norway and California, 40 growers agreed with a statement that water-stressed strawberry plants were more susceptible to powdery mildew compared with nonstressed plants. In repeated in vitro and in vivo experiments, we found that water stress was consistently and significantly unfavorable to conidial germination, infection, and increases in disease severity. Deleterious effects on the pathogen were observed from both preinoculation and postinoculation water stress in the host. Soil moisture content in the range from 0 to 50% was correlated (R2 = 0.897) with germinability of conidia harvested from extant colonies that developed on plants growing at different levels of water stress. These studies confirm that P. aphanis fits the norm for biotrophic powdery mildews and hosts under stress. Mild water stress, compared with a state of optimal hydration, is likely to decrease rather than increase susceptibility of strawberry to P. aphanis. We believe it is possible that foliar symptoms of leaf curling due to diffuse and inconspicuous infection of the lower leaf surfaces by P. aphanis could easily be mistakenly attributed to water stress, which we observed as having a nearly identical leaf curling symptom in strawberry.

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Powdery mildews can be controlled by brief exposure to ultraviolet (UV) radiation with devastating effect on their developmental stages including conidia germination. The treatment effect can be impaired by subsequent exposure to UV-A/blue light. UV-A/blue light-activated photolyase may be responsible for this and therefore we tested the function of three cryptochrome/photolyase family (CPF)-like genes (OINE01015670_T110144, OINE01000912_T103440, and OINE01005061_T102555) identified in the obligate biotrophic fungus Pseudoidium neolycopersici, the cause of tomato powdery mildew. A photolyase-deficient mutant of Escherichia coli transformed with coding sequence of OINE01000912_T103440 and exposed to brief (UV)-C treatment (peak emission at 254 nm) showed photoreactivation and cell survival when exposed to subsequent blue light, indicating complementation of photolyase activity. In contrast, the same photolyase-deficient E. coli transformed with the coding sequences of other two CPF-like genes did not survive this treatment, even though their expression were confirmed at protein level. This confirmed that OINE01000912_T103440 is a gene encoding photolyase, here named PnPHR1, with functionality similar to the native photolyase in E. coli, and classified as a class I cyclobutane pyrimidine dimer (CPD) photolyase. Modeling of the 634-amino acid sequence of PnPHR1 suggested that it is capable of binding flavin adenine dinucleotide (FAD) and methenyltetrahydrofolate (MTHF). However, spectroscopic data of the protein produced in an E. coli expression system could only reveal the presence of a reduced form of FAD, i.e., FADH– as an intrinsic chromophore. Within the tested wavelength range of 365–525 nm, the survival of photolyase-deficient mutant E. coli transformed with PnPHR1 showed a broad action spectrum from 365 to 454 nm. This was very similar to the previously characterized action spectrum for survival of P. neolycopersici conidia that had been treated with UV-C. Quantitative RT-PCR revealed that the expression of PnPHR1 in P. neolycopersici conidia was induced by UV-C, and peak expression occurred 4 h after brief UV-C treatment. The expression of PnPHR1 was repressed when incubated in red light after the UV-C treatment, but not when incubated in UV-A/blue light. The results may explain why the disease-reducing effect of short wavelength UV is impaired by exposure to UV-A and blue light.

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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.

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Resistens mot kjemiske plantevernmidler hos skadedyr, plantepatogene sopper og ugras er et alvorlig problem i flere matkulturer. Resistens oppstår som følge av for hyppig og ensidig bruk av plantevernmidler med samme biokjemiske virkemåte. Resistente skadegjørere kan også spre seg over landegrensene ved immigrasjon eller ved at de følger med importert plantemateriale. Vi har hatt mistanke om at immigrerende kålmøll og gråskimmel som følger med importerte småplanter av jordbær kan være resistente mot kjemiske plantevernmidler som brukes til å bekjempe disse skadegjørerne i Norge. I 2016 immigrerte store mengder kålmøll (Plutella xylostella) til Norge, og det ble påvist resistens mot insektmiddelet (insekticidet) lambda-cyhalotrin hos kålmøll-larver som ble samlet inn fra to kålfelt i Viken og Trøndelag. I 2019 var det en ny kålmøllinvasjon, og vi samlet inn og testet kålmøll-larver fra tre kålfelt i Rogaland og Viken. Larvene på alle de tre stedene var resistente mot lambda-cyhalotrin.

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Infections of Neonectria ditissima, the cause of European fruit tree canker, may be initiated during propagation. In a survey of 19 commercial apple orchards in southern Norway in the year of planting or the following year, the graft-union area of 15,270 trees was examined. The disease was found in 53% of the orchards, at a low incidence (<10%) with two exceptions (13 and 42%). Scion wood from mother trees with no, a few or several cankers were used to propagate trees that were surveyed for up to 38 months. In total 20 out of 1116 (1.8%) trees developed canker. The higher the number of cankers was on the mother trees, the higher was the number of trees developing canker after grafting. Infections developed on both cultivars (Discovery, Summerred) and all three rootstocks (Antonovka, B9, M9), but more so on grafted than T-budded trees, and more in 2015 than in 2014. When the scion wood was inoculated at the time of T-budding or grafting, disease development went faster and to a higher incidence on T-budded (94%) than on grafted trees (50%). Dipping the scion wood end in a spore suspension prior to grafting resulted in more infections than when a suspension droplet was placed on the bud and bark surface of the scion wood after grafting. The present investigation documents that scion wood may harbour inoculum of N. ditissima. Furthermore, infections may be initiated at time of propagation, and management practices of both scion wood production and nurseries should encounter that fact.

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In many areas where spring is wet, fungicides are applied in relation to rain events that trigger ejection of ascospores of Venturia inaequalis, which cause primary infections of apple scab. Past studies established the rate of ejection during rain in relation to light and temperature, and determined the wetting time required for infection. Simulation software uses this information to calculate risk and help time sprays accordingly. However, the distribution of the infection time required by a population of spores landed on leaves was never studied, and assumptions were used. To estimate this, we inoculated ascospores of V. inaequalis on potted trees at different temperatures for specific wetting times. Lesions were enumerated after incubation. Lesions increased with wetness time and leveled off once the slowest spores infected the host, closely matching the monomolecular model. Wetness hours were best adjusted for temperature using the Yin equation. The minimum infection time on the youngest leaves was about 5 h, matching results from previous studies, whereas half the lesions appeared after 7 h of infection. Infection times for leaves with ontogenic resistance were longer. Our results improve current software estimates and may improve spraying decisions.

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For å følge opp mistanke om og tidligere påvisninger av plantevernmiddelresistens, ble følsomheten for plantevernmidler undersøkt i 2018 hos: (1) glansbiller i seks felt med oljevekster i Akershus og Østfold, (2) veksthuspinnmidd i to jordbærfelt i Hedmark og Vest-Agder og tre bringebærtunneler i Vest-Agder og Sogn og Fjordane, (3) gråskimmel fra seks eplehager i Buskerud og Hordaland, (4) stivdylle i en kornåker i Akershus og (5) linbendel i to kornåkre i Akershus og Trøndelag. Tre av fem glansbillepopulasjoner var moderat resistente eller resistente mot Karate (lambda-cyhalothrin), fire av seks populasjoner var moderat resistente mot Mavrik (tau-fluvalinat), og tre av fire populasjoner hadde nedsatt følsomhet for Biscaya (tiakloprid). Ingen av glansbillepopulasjonene var resistente mot Avaunt (indoksakarb). Vi fant indikasjoner på at veksthusspinnmidd fra jordbær og bringebær kan være i ferd med å utvikle resistens mot Envidor (spirodiklofen), Floramite (bifenazat) og Danitron (fenpyroksimat). Med enkelte unntak ble det ikke påvist alvorlig grad av resistens hos veksthusspinnmidden, men undersøkelsen har vært av begrenset omfang, og bør utvides. Ingen av veksthusspinnmidd-populasjonene var resistente mot Vertimec (abamektin). Hos gråskimmel fra eple ble moderat resistens og resistens mot Topsin (tiofanatmetyl) påvist hos nesten halvparten av de 44 isolatene som ble testet, mens 18 % av 56 isolater var resistente mot Teldor (fenheksamid), og mellom 12 og 8 % var moderat resistente og/ eller resistente mot Scala (pyrimetanil), boskalid, Comet (pyraklostrobin) og Rovral (iprodion). Multiresistens ble funnet hos 15 % av isolatene. Det ble ikke funnet resistens mot fludioksinil. Det ble påvist resistens mot ALS-hemmerne Express (tribenuronmetyl) og Hussar OD (jodsulfuron-metyl-natrium) hos stivdylle i kornåkeren i Akershus, og mot Express, Hussar OD og Primus (florasulam) hos linbendel i kornåkrene i både Akershus og Trøndelag.

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Sweet cherry fruit delivered at three packinghouses over two years in southern Norway was assessed for postharvest fungal decay after being graded in a line with water containing 2 ppm chlorine, in comparison with non-graded fruit. Assessment of decay was carried out after cold storage of the fruit for ten days at 2°C, followed by two days at 20°C. In mean of all assessments, there was no difference in total decay after storage between fruit graded in a water line or non-graded fruit, however, the first year there was a higher total incidence of fruit decay on water-graded fruit after storage. The grading-water was not changed during the day, but time of grading during the day did not seem to influence the amount of decay. Mucor rot and grey mould accounted for 80 and 19%, respectively, of the decay averaged for all assessments, and there was no significant difference in decay of the two diseases if graded in water or not. For blue mould and brown rot, the incidence was lower in water graded fruit, while it was the opposite for Cladosporium rot. On average, fruit decaying fungi developed on PDA from 57 and 17% of water samples from grading lines in the two years, respectively. On pieces with filter paper wetted in different locations of the grading line, 87% contained fruit decaying fungi when placed on PDA, and Mucor sp. was the most prevalent pathogen. Fruit cooled in a hydro-cooler containing either 2, 10 or 50 ppm chlorine, all reduced decay with about 75% compared to non-chlorinated water. Although the grading water may contain spores of pathogenic fungi, the present results indicated that water containing 2 ppm chlorine does not significantly increase fruit decay. Thus, only a slight chlorination of grading water may be sufficient to reduce postharvest contamination.

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I denne rapporten presenteres resultater fra biologisk veiledningsprøving av soppmidler i jordbær, bringebær, hvete, setteløk, gulrot og gran i skogplanteskoler. Det er også presentert et forsøk med skadedyrmidler mot bladlus i erter til konserves. I tillegg er det rapportert et forsøk med kairomonfeller mot skadedyr i eple.

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Introduction and purpose: The ability of apple rootstocks to become infected by Neonectria ditissima, the cause of European canker, was studied over two years. Materials and methods: Rootstocks B9 and M9 with a size suitable for grafting (6-10 mm stem diameter, termed rootstocks), and smaller sized rootstocks (<5 mm stem diameter, termed transplants) of B9, M9, M26, MM106 and Antonovka were inoculated with N. ditissima at different times, either with contaminated map pins or with spore suspensions. In addition, the rootstocks were either defeathered (side shoots removed), topped (top shoot headed) or both, to create wounds that would normally occur during propagation, while wounds on transplants were made by removing leaves. Results and discussion: One month after inoculation, slightly sunken canker lesions had developed around the inoculation points of the map pins or wounds. No lesions developed on the non-inoculated controls. Map pin inoculation resulted in 30% to 89% infection and spore suspension sprayed on wounds from 5% to 45% infection. When the cankered areas were split open, brown lesions with necrotic tissue due to infection by N. ditissima appeared. The transplants of M9, M26 and MM106 inoculated with contaminated map pins in 2014 developed necrosis on 40% to 67% of the plants, but there were no differences in the incidence or severity among the different types. On the transplants of B9, Antonovka and M9 inoculated in 2015, there was more necrosis on B9 (42%) than on Antonovka (11%) and more sporulating lesions on B9 (29%) than on M9 (9%) or on Antonovka (4%). Conclusion: It can be concluded that rootstocks used for apple trees may become infected by N. ditissima, and wounds should thus be protected during propagation.

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Cultivars and cultivating methods for organic strawberry production were studied in experiments in open fields and high plastic tunnels during four cropping seasons in southern Norway. In open fields, flowers and fruits were attacked by grey mould when the flowering and harvest seasons were wet, and marketable yield was reduced by up to 20%. Production in high tunnels showed a potential of high yields of fruits of good quality when strawberry powdery mildew was controlled. Berry size varied significantly among the cultivars. ‘Frida’ had the largest fruits followed by ‘Sonata’ and ‘Florence’, while ‘Polka’, ‘Korona’ and ‘Iris’ had the smallest fruits. All cultivars yielded well, but due to fruit decay caused by grey mould the marketable yield was significantly reduced, especially in open field. Grey mould was the most important factor influencing marketable yields. Fruits from matted rows were largest, while the highest yield was obtained on woven polyethylene. There were no effects of mulching methods on marketable yield or the amount of fruits with grey mould. High tunnels with good control of pests and diseases showed a potential of high and stable yields of good quality.

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Nighttime ultraviolet (UV) radiation, if applied properly, has a significant potential for management of powdery mildews in many crop species. In this study, the role of growth light duration, irradiance, a combination of both (daily light integral) and light spectral quality (blue or red) on the efficacy of UV treatments against powdery mildew caused by Podosphaera xanthii and the growth performance of cucumber plants was studied in growth chambers. Increasing daily light integral provided by high-pressure sodium lamps (HPS) decreased efficacy of nighttime UV treatments against P. xanthii, but it increased plant growth. Furthermore, the efficacy of nighttime UV decreased when day length was increased from 16 to 20 h at a constant daily light integral. The efficacy of nighttime UV increased if red light was applied after UV treatment, showing the possibility of day length extension without reducing the effect of UV. Increasing the dose of blue light during daytime reduced the efficacy of nighttime UV in controlling the disease, whereas blue deficient growth light (< 6% of blue) caused UV mediated curling of young leaves. Furthermore, application of blue light after nighttime UV reduced its disease control efficacy. This showed the importance of maintaining a minimum of blue light in the growth light before nighttime UV treatment. Findings from this study showed that optimization of nighttime UV for management of powdery mildew is dependent on the spectral composition of the photosynthetically active radiation.

Sammendrag

Production of inoculum of Colletotrichum acutatum from both previously infected and overwintered tissue, as well as newly developed plant tissue of sour cherry (Prunus cerasus), was studied in southern Norway. Plant parts were sampled from commercial, private, or research orchards, and incubated for 2 to 14 days (time depended on tissue type) in saturated air at 20°C. In early spring, abundant sporulation was found on scales of overwintered buds and shoots. A mean of 35% infected buds in four cultivars was observed, with a maximum of 72% of the buds infected in one of the samples. Over 3 years, the seasonal production of overwintered fruit and peduncles of cv. Fanal infected the previous year was investigated. In all three years, the infected plant material was placed in the trees throughout the winter and the following growing season; in two of the years, fruit and peduncles were also placed on the ground in the autumn or the following spring. Old fruit and peduncles formed conidia throughout the season, with a peak in May and June. Spore numbers declined over the season, but the decline was more rapid for plant material on the ground than in the trees. On average over 2 years, 68.7, 24.0, or 7.3% of the inoculum came from fruit placed in the trees, placed on the ground in spring, or placed on the ground the preceding autumn, respectively. The number of fruit and peduncles attached to the trees in a planting of cv. Hardangerkirsebær was followed from February to July one year, and although there was a decline over time, fruit and/or their peduncles were still attached in substantial numbers in July, thus illustrating their potential as sources of inoculum. In observations over 2 years in a heavily infected orchard of cv. Stevnsbær, 75 and 47% of flowers and newly emerged fruit, respectively, were infected. Artificially inoculated flowers and fruit produced conidia until harvest, with a peak in mid-July. It may be concluded that previously infected and overwintered, as well as newly emerged tissue of sour cherry, may serve as sources of inoculum of C. acutatum throughout the growing season.

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Det er per i dag påvist resistens eller nedsatt følsomhet mot kjemiske plantevernmidler hos flere skadedyr, plantepatogener og ugras i norske jord- og hagebrukskulturer. Hos skadedyr er resistens mot pyretroider og nedsatt følsomhet for tiakloprid vanlig hos rapsglansbille i oljevekster. Resistens mot pyretroider er påvist hos ferskenbladlus og potetsikade fra potet, gulrotsuger fra gulrot, ferskenbladlus fra persille, kålmøll og ferskenbladlus fra kålvekster, jordbærsnutebille fra jordbær, og ferskenbladlus, bomullsmellus, veksthusmellus og sør-amerikansk minerflue fra veksthus. Det er også funnet resistens mot pirimikarb hos ferskenbladlus og nedsatt følsomhet for imidakloprid hos ferskenbladlus og bomullsmellus. I jordbær og bringebær er det indikasjoner på begynnende resistensutvikling mot flere av middmidlene. Hos plantepatogener er resistens mot QoI-fungicider påvist hos gråskimmel fra jordbær, bringebær og gran i skogplanteskoler, hos mjøldoggsopper i jordbær og veksthusagurk, og hos bladflekksopper i hvete. Resistens mot triazoler er funnet i flere bladflekksopper i hvete. Resistens mot hydroksyanilid- og SDHI-er utbredt hos gråskimmel fra jordbær og bringebær, og i skogplanteskoler er det påvist resistens mot tiofanater.....

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På grunn av uventa avlingssvikt i jordbær forårsaket av gråskimmel på Sørlandet i 2016, ble det tatt ut prøver fra 20 jordbærfelt i Agder etter høsting for å undersøke mulig resistensforekomst hos gråskimmelsoppen mot kjemiske soppmidler. Totalt ble 148 til 157 soppisolater fra 19 felt analysert for resistens mot alle de kjemiske gruppene av virksomme stoffer som brukes mot gråskimmel; boskalid (SDHI), fenheksamid (hydroksyanilid), iprodion (dikarboksimid), pyrimetanil (anilinopyrimidin) og pyraklostrobin (QoI/strobilurin). Vi fant at 89,7, 86,0 og 65,0 % av isolatene var resistente mot henholdsvis boskalid, pyraklostrobin og fenheksamid. Videre var 25,0 % resistente mot pyrimetanil og 2,6 % resistente mot iprodion, mens ingen av soppisolatene var resistente mot fludioksonil. Kun 8,9 % av soppisolatene var sensitive overfor alle de virksomme stoffene, mens 5,1 % var resistente mot ett stoff (kjemisk gruppe). De øvrige isolatene var multiresistente mot to (21,0 %), tre (43,9 %), fire (19,1 %) og fem (1,9 %) virksomme stoffer. Resulatene stemmer godt med tidligere funn både i Norge og andre land. Høy grad av resistens mot boskalid, fenheksamid og pyraklostrobin er alvorlig, fordi disse har vært svært viktige for å bekjempe gråskimmel i jordbær. Dårlig virkning av disse midlene kan gjøre bekjempelse av gråskimmel framover svært vanskelig for produsentene. Det er viktig å understreke at det var relativt stor variasjon i resistensforkomst mellom de ulike jordbærfeltene, og at det er mange andre faktorer i tillegg til resistens (som værforhold, sprøyteteknikk og dyrkingssystem) som vil påvirke hvor mye avlingstap gråskimmel forårsaker.

Sammendrag

Fungi within the Colletotrichum acutatum species complex occur asymptomatically on plant parts of many different plant species. Leaves from apple orchards in southern Norway were sampled, frozen for five hours and incubated for six days to reveal presence of asymptomatic infections of C. acutatum. Number of leaves (incidence) and leaf area covered (severity) with conidial masses of C. acutatum were assessed biweekly on cv. Aroma from late May to late September during three growing seasons. The first finding of conidial masses occurred in the second half of July, and there was a higher incidence occurring in August and September. Sampling of leaves from fruit spurs and vegetative shoots of cvs. Aroma and Elstar showed that conidial masses of C. acutatum developed on leaves on both shoot types, and there was no difference in incidence between these two types. The fungus was detected on leaves from six of eight commercial orchards of cv. Aroma over three years, with a mean incidence of 5.5 %. After storage, bitter rot was found on apple fruit from all eight orchards. There was no correlation between incidence of conidial masses of C. acutatum on leaves and on fruit. In all orchards and seasons investigated, incidence and severity on leaves varied from 0 to 67%and 0 to 85 %, respectively. The discovery of apple leaves containing conidial masses of C. acutatum clearly indicate for leaves as a potential source of inoculum for fruit infections.

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Oidium neolycopersici, the cause of powdery mildew in tomato, was exposed to UV radiation from 250 to 400 nm for 1, 12, or 24 min. Radiation ≤ 280 nm strongly reduced conidial germination, hyphal expansion, penetration attempt and infection of O. neolycopersici. From 290 to 310 nm the effect depended on duration of exposure, while there was no effect ≥310 nm. There were no significant differences within the effective UV range (250–280 nm). Conidial germination on a water agar surface was b20% or around 40%, respectively, if samples were exposed for 1 min within the effective UV range followed by 24 h or 48 h incubation. Twelve or 24 min exposure reduced germination to close to nil. A similar trend occurred for germination of conidia on leaf disks on water agar in Petri dishes. The effective UV range significantly reduced all subsequent developmental stages of O. neolycopersici. There was no cytoplasmic mitochondrial streaming in conidia exposed to the effective UV range, indicating that there may be a direct effect via cell cycle arrest. There was no indication of reactive oxygen species involvement in UV mediated inhibition of O. neolycopersici. Optical properties of O. neolycopersici indicat- ed that the relative absorption of UV was high within the range of 250 to 320 nm, and very low within the range of 340 to 400 nm. Identification of UV wavelengths effective against O. neolycopersici provides a future basis for precise disease control.

Sammendrag

Effects of controlled atmosphere (CA) conditions on physiological disorders and fungal fruit decay on apple ‘Aroma’ were investigated. Fruit from three growing seasons were stored at 1% or 2% O2 (both at 2% CO2) at either 1°C or 3°C in small research units; controls were kept in the same ventilated rooms at the two temperatures (ambient air). The fruit were removed from storage after four or six months and assessed for fruit decay immediately afterwards and after two weeks at 20°C. Fruit quality parameters were recorded at the end of storage. On a three-year average, fruit stored in CA was less ripe at the end of storage. After both four and six months storage, CA reduced total decay (physiological disorders and fungal decay) by on average 70% and 45%, respectively, compared to storage in ambient air. Senescent breakdown was lower after CA storage for four months, but not after six months and not after simulated shelf life. Soft scald was lower when stored in CA both after cold storage at 1°C and simulated shelf life. After storage at 3°C there was lower incidence of soft scald when stored in CA after four months, but not after six months. For fungal fruit decay in general, there was no effect of low oxygen, however, 2% O2 gave slightly less bitter rot (Colletotrichum acutatum) than 1% O2 and significantly less than ambient air after simulated shelf life. Averaged over all oxygen levels, 1°C gave significantly less bitter rot than 3°C. It may be concluded that use of CA for storage of ‘Aroma’ is a good way of reducing development of physiological disorders. However, development of bitter rot seemed to be more influenced by temperature and storage time than by low O2.

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Sammendrag

Disease-suppressive effects of nighttime applications of ultraviolet-B (UV-B) were investigated at two irradiance levels (1.6 or 0.8 W/m2) in strawberry and rosemary plants inoculated with Podosphaera aphanis or Golovinomyces biocellatus, respectively. Plants were exposed to each irradiance level every third night for either 9 or 18 min, every night for either 3 or 6 min, or three times every night for either 1 or 2 min. Thus, over time, all plants received the same cumulative dose of UV-B, and severity of powdery mildew was reduced by 90 to 99% compared with untreated controls in both crops. Use of polished aluminum lamp reflectors and UV-B reflective surfaces on greenhouse benches significantly increased treatment efficacy. An automated apparatus consisting of an adjustable boom with directed airflow was used to move UV-B lamps over greenhouse benches at 25 or 50 cm/min. Directed airflow moved leaves on the subtending plants to better expose upper and lower surfaces to UV-B but directed airflow actually decreased the efficacy of UV-B treatments, possibly by dispersing conidia from lesions before they were exposed to a lethal dose of UV-B. Results indicate broad applicability of nighttime applications of UV-B to suppress powdery mildews, and that cumulative UV-B dose is an overriding factor determining efficacy. Finally, enhanced suppression on shaded or obscured tissues is more likely to be affected by reflective bench surfaces than through attempts to physically manipulate the foliage.

Sammendrag

I desember 2006 ble soppen Herpotrichia parasitica (syn. Trichosphaeria parasitica) funnen på nordmannsedelgran (Abies nordmanniana) i et juletrefelt på ei øy i Rogaland. I april året etter ble det registrert store skader av den samme soppen på tyrkeredelgran (A. bornmuelleriana) hos en juletredyrker på fastlandet i Rogaland. Rundt 70 % av trærne var smittet. Noen trær hadde så sterke angrep at de måtte fjernes fra feltet. Soppen hadde til da ikke blitt funnet i juletrefelt, men den var ikke ny i landet. Soppen ble registrert på vanlig edelgran (A. alba) i Hordaland i 1974 (Robak 1976). I 2004 ble det funnet sterke angrep av soppen på vanlig edelgran i Njåskogen i Time kommune på Jæren). Fra Tyskland er det rapportert at soppen hovedsakelig angriper vanlig edelgran, men nordmannsedelgran, nobeledelgran (A. procera), veitchedelgran (A. veitchii) og granarter (Picea spp.) kan bli skadet når smittepresset er stort. I Danmark er soppen blant annet registrert på nobel- og nordmannsedelgran. De fleste innmeldte funn av H. parasitica i Nord-Amerika er ikke bekreftet.

Sammendrag

Edelgrannålesopp (Phaeocryptopus nudus) er funnet på korkedelgran (Abies lasiocarpa var. arizonica) og fjelledelgran (A. lasiocarpa) i Norge. I USA er soppen rapportert fra juletrær av nobeledelgran (A. procera) og kjempeedelgran (A. grandis).

Sammendrag

For vel 15 år siden ble det rapportert at edelgranskuddsjuke så langt var funnet på vanlig edelgran (Abies alba), gresk edelgran (A. cephalonica), fjelledelgran (A. lasiocarpa), korkedelgran (A. lasiocarpa var. arizonica), nordmannsedelgran (A. nordmanniana), spansk edelgran (A. pinsapo), nobeledelgran (A. procera) og sibiredelgran (A. sibirica) i Norge (Solheim 1999), men ikke på juletrær. Noen av disse funnene skriver seg langt tilbake i tid. I juletrefelt har vi så langt funnet angrep på sibiredelgran, nordmannsedelgran, fjelledelgran og tyrkeredelgran (A. bornmuelleriana). Edelgranskuddsjuke har vært mest problematisk på Nord-Vestlandet, men de siste årene har vi også sett sterke angrep på Østlandet. Vi har erfart er at fjelledelgran er spesielt utsatt. Edelgranskuddsjuke er også rapportert på fjelledelgran fra Nord-Amerika.

Sammendrag

Granbarstripesopp ses ofte på vanlig gran (Picea abies), men andre granarter kan også få angrep. Soppen er vanlig i Sør-Norge, og den er funnet nord til Nordland. På enkeltnåler av kjempeedelgran (Abies grandis) og nordmannsedelgran (A. nordmanniana) har vi funnet sporehus som ligner Lirula, men uten å finne sporer som kan fastslå dette sikkert. Fra Nord-Amerika er det kjent at Lirula abietis-concoloris angriper ulike edelgranartar.

Sammendrag

Sporene sprer seg med vannsprut fra sporehus på overvintra, sjuke nåler. Infeksjon kan forekomme fra april til oktober, men de kraftigste angrepene får man under fuktig vær etter knoppsprett. Det er særlig de nye, myke nålene som blir angrepet, men også eldre nåler er utsatte når trærne er svekka. Infeksjonsprosessen går relativt sakte. Optimal temperatur for soppen er 25 ˚C. Da tar det 48 timer med fuktige forhold før soppen klarer å etablere seg i nålene. Ved lavere temperatur tar det lenger tid, men særlig på Vestlandet er det sjelden mangel på lange, fuktige perioder. Etter nedbør og doggfall vil det ofte holde seg fuktig lenge inne i tette juletreplantinger eller på småplanter som er nedgrodde i ugras, noe som vil være gunstig for infeksjon.

Sammendrag

Rotkjuke er den mest vanlige råtesoppen som fins i norsk skog. Den forårsaker rotråte på løv- og bartrær, særlig på gran. Infiserte, eldre stubber er ofte infeksjonskilder for nye småplanter. Råtesoppen kan spres både ved sporer og rotkontakt.

Sammendrag

Sydowia polyspora er en sopp som er årsak til to ulike sjukdommer på edelgran. I plantevernleksikonet er det to artikler om soppen, denne og artikkelen om nekrotiske årsnåler.

Sammendrag

Forsøksresultatene som presenteres i denne rapporten er biologisk godkjenningsprøving av soppmidler utført på oppdrag fra Mattilsynet i 2014. Inkludert i rapporten er også forsøk eller egne forsøksledd som grupperes som biologisk utviklingsprøving. Forsøkene er utført etter GEP-kvalitet1 hvis ikke annet er nevnt. Dette innebærer at det er utarbeidet skriftlige prosedyrer for nesten alle arbeidsprosesser. Disse prosedyrene, kalt standardforskrifter (SF’er), er samlet i en kvalitetshåndbok. Denne er delt ut til alle personer som arbeider med utprøving av plantevernmidler. De samme personene har også vært med på et endagskurs i GEP-arbeid.