Finnish Nurseries Research Articles

First report of Plum pox virus on plum in Finland

In July 2014, leaves showing symptoms of a viral infection were collected from a plum tree serving as a mother tree in a Finnish nursery and found to be infected by Plum pox virus (PPV). A subsequent survey revealed additional infected trees originating from the infected mother tree. This paper provides the first report of PPV, the causal agent of the most destructive viral disease of Prunus, in Finland.

Seed soak-sorting prior to sowing affects the size and quality of 1.5-year-old containerized <i>Picea abies</i> seedlings

We studied the effect of soak-sorting Norway spruce ( (L.) H. Karst.) seeds on emergence, development and quality of container seedlings in two commercial seed lots. The seeds, separated by soaking into bottom and surface fractions, were sown in June, and the seedlings were grown during two growing seasons under typical Finnish nursery conditions. The first summer seedlings were grown in a greenhouse and outdoors for the second, full growing season. All sunken seeds were full and viable according to radiography, whereas the floating seeds contained 2% and 13% larvae-filled and 8% and 11% anatomically immature seeds, depending on the seed lot. Seedlings grown from the bottom fraction seed emerged 2.5–3.5 days earlier than seedlings of storage dry (i.e. control) seed. Height, diameter, and shoot and root dry mass of the seedlings were affected by soaking after both the first and second growing seasons. The largest seedlings originated from the bottom fraction. The proportion of saleable seedlings was four percentage points higher in the bottom fraction than in the other seedlings. The effects of soaking found in this study are more notable than as previously reported for Norway spruce seedlings. This suggests that soaking and soak-sorting may be most useful when the growing conditions are stressful, i.e. when seeds are sown in summer rather than 1-year-old seedling crops sown in spring under the climate conditions typical of Finland.Picea abies

Identity and potential pathogenicity of Phytophthora species found on symptomatic Rhododendron plants in a Finnish nursery

In this study, microbial isolations were made from symptomatic Rhododendron plants from a large Finnish nursery, known to be harbouring Phytophthora based on PCR screenings. The nearby waterways were also sampled. A diversity of common Nordic plants was screened for Phytophthora susceptibility. Isolates recovered from Rhododendron plants included P. ramorum, P. cactorum, P. plurivora, P. pini and Pestalotiopsis sp. Baits floated in water samples from nearby waterways did not become infected with Phytophthora. In infection trials, all Phytophthora detected here were pathogenic to Rhododendron but nonpathogenic to Pinus sylvestris and Quercus robur. Phytophthora plurivora infected Betula pendula, Alnus glutinosa, Picea abies, Viburnum lentago, Vaccinium myrtillus, V. uliginosum, V. angustifolium and Fragaria × ananassa, the latter four species being new host records for this pathogen. Phytophthora ramorum caused small lesions on B. pendula, A. glutinosa and V. uliginosum, and more serious symptoms in Rhododendron, Viburnum lentago, V. lantana, Vaccinium myrtillus and V. angustifolium. Phytophthora pini was pathogenic to most plants tested, including Rhododendron, V. lentago and P. abies. In spite of an annual eradication programme in the nursery, P. ramorum was detected in annual samples taken during 2004–2010. Microsatellite analysis revealed that all isolates of P. ramorum belonged to the EU1 lineage.

Environmental Risks Caused by Pesticides at Forest Nurseries in Finland

ABSTRACT Previously, various persistent pesticides were used extensively in the production of seedlings at Finnish forest nurseries. The extent and magnitude of the risks arising from the consequent environmental contamination are largely unknown. Therefore, we selected two representative nurseries for which we conducted tiered health risk assessments (HRA) using risk-based benchmarks and two calculation tools (SSL and Risc-Human software). Ecological risk assessments (ERA) involved comparisons of environmental concentrations with ecotoxicological benchmarks. Site investigations revealed that the concentration of several pesticides exceeded the Finnish soil quality guidelines in some places. The compost pile for organic residues and the pond receiving runoffs contained traces of pesticides and the maximum concentration of atrazine and terbuthylazine in groundwater exceeded the corresponding guideline for household water. Hexachlorobenzene proved to pose the highest health risks, the maximum hazard quotient being around 10 (carcinogenity-based) in the residential land use scenario. Owing to the conservative assumptions, health risks are expected to remain insignificant, however. Risks to the local terrestrial ecosystem would also remain low, while only further studies will reveal the actual risks to the adjoining aquatic ecosystem. Both calculation tools showed shortcomings that generate uncertainty in the HRA, whereas the ERA was hampered particularly by the lack of benchmarks.

Phytophthora in Finnish nurseries

International trade and travel have facilitated the spread of harmful organisms around the world. Human-mediated movement of plants and plant products is now generally accepted to be the primary mode of introduction of pathogens and pests. Species of Phytophthora, a genus of plant pathogens, are commonly spread in this way and have caused severe epidemics in silviculture, horticulture and natural systems all over the world. The objective of the study was to gather information on the occurrence of Phytophthora spp. in Finnish nurseries. Furthermore, the aim was to produce information for risk assessments for these Phytophthora spp. and establish molecular means for their detection. Phytophthora cactorum was found to persist in natural waterbodies and results suggest that irrigation water might be a source of inoculum for the disease in nurseries. In addition to P. cactorum, isolates from ornamental Rhododendron in nurseries yielded three species new to Finland: P. ramorum, P. plurivora and P. pini. The only species with quarantine status, P. ramorum, was able to persist in the nursery in spite of an annual European Commission sanitation protocol. Phytophthora plurivora and the closely related P. pini had more hosts among Nordic tree species and other plants abundant in Finnish nurseries and forest ecosystems. They were also found to have higher infectivity rates compared to P. ramorum and P. cactorum. All four species survived two weeks in -5 °C , and thus soil survival of these Phytophthoras in Finland is likely under current climatic conditions. The most common tree species in Finnish nurseries, Picea abies, was highly susceptible to P. plurivora and P. pini in pathogenicity trials. In a histological examination of P. abies shoot tissues inoculated with P. plurivora zoospores, fast necrotrophic growth was observed in nearly all tissues of the fresh shoot. The production of propagules in P. abies shoot tissue was only weakly indicated. In this study, a PCR–DGGE technique was developed for simultaneous detection and identification of Phytophthora spp. It reliably detected Phytophthora in plant tissues and could discriminate most test species as well as indicate instances of multiple-species infections. It proved to be a useful detection and identification tool either applied alone or in concert with traditional isolation culture techniques. The limitations of the method are also discussed. In conclusion, all of the introduced species of Phytophthora had properties that promote a high risk of establishment and spread in Finland. The efficient transport of Phytophthora via commercial traffic and favorable conditions due to expected climate change will increase the incidence and establishment of Phytophthora in new areas. Thus, it is probable that pathogens of this genus will be introduced and become established in Finland and other Nordic countries unless efficient phytosanitary control becomes standard practice in the international plant trade.

Fungal diseases in forest nurseries in Finland

Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and silver birch (Betula pendula) are the major tree species grown in Finnish forest nurseries where 99% of the seedlings are grown in containers first in plastic-covered greenhouses and later outdoors. The main diseases on conifer seedlings are Scleroderris canker (Gremmeniella abietina), Sirococcus blight and cankers (Sirococcus conigenum), snow blights (Herpotrichia juniperi and Phacidium infestans) and needle casts (Lophodermium seditiosum and Meria laricis). Also grey mould (Botrytis cinerea) and birch rust (Melampsoridium betulinum) are among the diseases to be controlled with fungicides. During last years Scleroderris canker has been a problem on Norway spruce, which has been since 2000 the most common species produced in Finnish nurseries. Root die-back (uninucleate Rhizoctonia sp.) on container-grown spruce and pine was a problem in the 1990s. Today the disease has become less common in modern nurseries due to improvements in hygiene and cultivation practice. Since 1991 stem lesions and top dying caused by Phytophthora cactorum has been a problem on birch. The ongoing climate change has already had effect on rusts and powdery mildews as well as other fungi infecting leaves. All diseases, which gain high precipitation and warm and long autumns. For same reasons winter stored seedlings need sprayings against grey mold. Fungal infections are also possible during short-day (SD) treatment, that is necessary for summer and autumn plantings and a beneficial step prior freezing temperatures outside or in freezer storage. Growers are encouraged to use cultural and integrated pest management techniques such as better nursery hygiene, including removing plant debris in nursery growing areas and hot water washing of containers plus removal of diseased, spore-producing seedlings and trees around the nursery.

Irrigation water and Phytophthora cactorum in a forest nursery

Phytophthora cactorum (Lebert and Cohn) J. Schröt is known to cause stem lesions on Betula pendula Roth in Finnish nurseries. It has been suggested that irrigation water may be one source of infection. Therefore, P. cactorum was baited from pond water used for irrigation and direct isolations were made from necrotic stem lesions in a forest nursery during the years 2004–2006. Morphological characteristics, as well as sequencing of the β-tubulin gene and ITS1 region, confirmed the isolates as P. cactorum. The pathogen was present in the pond every year, but no diseased seedlings were found in 2005. The cultural and morphological characteristics showed high variation among the isolates, but it was not possible to identify the origins of the isolates according to them. In random amplified microsatellite (RAMS) analysis and DNA sequencing, the isolates from the pond and from the stem lesions were genetically similar, and the tested isolates were pathogenic. The results indicate that irrigation water is one source of stem lesion disease, and the microbe can overwinter in the pond. Two separate forms of the β-tubulin gene were detected in all the studied isolates, suggesting that the P. cactorum here carries two β-tubulin gene loci in its genome.

Inoculations of eight Pinus species with Cronartium and Peridermium stem rusts

The relative susceptibility of eight Pinus species, P. sylvestris, P. mugo, P. contorta, P. peuce, P. cembra, P. strobus, P. resinosa and P. banksiana, to pine stem rusts, Cronartium flaccidum, Peridermium pini and Cronartium ribicola, was investigated by artificial inoculations. Aeciospores were collected from single aecia, bulked sample of aecia from individual lesions, and telia carrying basidiospores and used as inocula in five experiments containing a total of 6337, 1–7 years old pine seedlings. Rust disease symptoms were recorded in May–August in 2000–2006. No disease symptoms were recorded on P. contorta, P. peuce, P. strobus, P. resinosa, P. banksiana and P. cembra regardless of the rust species, spore source or pine provenance. In an experiment, 8% of the P. mugo and 13% of the 2-year-old P. sylvestris seedlings inoculated with P. pini showed disease symptoms, a northern spore source being the most virulent one. Inoculations with C. flaccidum were negative. In another experiment, significant variation in virulence occurred on Scots pine by individual P. pini spore sources from different rust populations. In a third experiment, 7–10% of the 1-year-old Scots pine seedlings inoculated with P. pini and 1% of those inoculated with C. flaccidum were infected without any differences in the disease rates between the pine provenances. In an experiment with 21 Scots pine provenances from various geographic regions, the disease symptoms developed only occasionally on very few seedlings regardless of the pine provenance or spore source. The aecia and swellings developed on over 90% of the infected seedlings inoculated with P. pini with small variation by the pine species, host provenances or spore sources. Spermatial fluid was observed only in small number of infected seedlings. Although the pine provenances commonly cultivated in Finnish nurseries proved to be very resistant to rust infection, the weather conditions at the early stage of infection had an impact on disease development. Based on the negative inoculation results, P. contorta can be recommended as an alternative to P. sylvestris for cultivation in areas suffering from severe pine stem rust epidemics in northern Fennoscandia.

First Report of Phytophthora ramorum and P. inflata in Ornamental Rhododendrons in Finland.

Phytophthora ramorum was found for the first time in Finland during the spring of 2004 on marketed plants of Rhododendron spp. originating in other EU member states. During August of 2004, the pathogen was also found in one Finnish nursery on German Rhododendron catawbiense plants and several Finnish Rhododendron spp. cultivars. P. ramorum was detected by species-specific PCR and isolated (1). It was first characterized by an abundant production of chlamydospores on PARP and V8 agar, absence of oogonia and antheridia, and elongate, ellipsoid, deciduous, semipapillate sporangia produced in soil extract water (3). A partial sequence of the β-tubulin gene was identical to that of P. ramorum deposited in GenBank. Despite strict regulations governing the movement of plants, the pathogen has been found every year since 2004 on materials transported to Finland from other EU countries. A total of 586 samples were taken from symptomatic plants of several susceptible species from 2004 to 2006. P. ramorum was detected in 51 rhododendron samples and the number of the outbreak sites was 28. In domestic plant production, P. ramorum was found in only one nursery. The infected plants in this nursery were destroyed in 2005 according to the EU regulation 2004/426/EG. During the 2006 growing season, 84 samples from trace-forward inspections and reinspections of the nursery were tested and P. ramorum was not detected in any of the samples. In 2005, surveys for P. ramorum on Finnish Rhododendron spp. cultivars with necrotic lesions on leaves and blackened tips yielded, in addition to P. ramorum, another Phytophthora sp. On V8 agar, this homothallic species showed a stellate growth pattern with sparse aerial mycelium. Oogonia had both paragynous and amphigynous antheridia, and sporangia produced in soil extract water were ellipsoid in shape and semipapillate. A 763-bp segment of the β-tubulin gene was sequenced and was identical to the β-tubulin sequence of P. inflata strain IMI342898 (GenBank), which was isolated in 1990 from Syringa sp. in the UK. It is likely that this P. inflata strain has been spreading in Europe with the ornamental plant trade. To fulfill Koch's postulates, rhododenrdon plants were inoculated (2) with P. inflata or P. ramorum, typical symptoms observed, and the pathogens were reisolated from inoculated plants. Both Phytophthora species also caused necrotic lesions on Alnus glutinosa, A. incana, and Betula pendula. Pinus sylvestris was resistant to both Phytophthora spp., whereas Picea abies was susceptible to P. inflata but not P. ramorum.

Alien Species in Finnish Nurseries, Phytophthora spp.

International trade has increased the risk of pest spread. The climatic change will also improve the establishment of introduced species into new geographical areas. Since the beginning of 1990's Phytophthora cactorum has caused losses in agriculture on strawberries and caused stem lesions on silver birch seedlings in forest nurseries in Finland. P. ramorum was found in Finland for the first time in spring 2004 on marketed Rhododendron spp. plants originating from other EU member states. In August 2004 the pathogen was also found in one Finnish nursery on German Rhododendron catawbiense plants and on several other Finnish Rhododendron spp. cultivars. Most common microbes isolated from the lesions on the Finnish Rhododendron leaves collected in 2005 were Pestalotiopsis sp., P. cactorum, P. inflata and P. ramorum. In pathogenicity trials P. inflata was capable to infect most host plants used in tests including Fragaria x ananassa, Betula pendula, Alnus glutinosa, A. incana, Picea abies and Vaccinium vitis-idea. P. ramorum caused also stem lesions on birch and alder, but was less pathogenic than P. inflata. Pinus sylvestris was resistant to both P. ramorum and P. inflata.

Optimizing the supply chain strategy of a multi-unit Finnish nursery company

This paper introduces a capacitated mixed integer programming (CMIP) model for solving an integrated production-distribution system design problem (PDSDP) in the seedling supply chain management (SCM) of a multi-unit Finnish nursery company. The model was originally developed from a strategic perspective in which a company desires to evaluate the expansion or closure of its facilities. Nevertheless, the model is also used for solving operational and tactical level problems by applying applicable constraints. The data were collected from the company studied. The results proved that economies of scale could be exploited in seedling production more than the company does today; Compared to the company’s current supply chain strategy with 5 nursery units producing seedlings, when other supply chain strategies were applied the number of nursery units decreased by 2–4 units, and cost savings in the supply chain varied from 11.3% to 21.3%.

Linear Programming and Mixed Integer Programming in Management of Seedling Transportation

In this paper, the applicability of linear programming (LP) in management of seedling transportation was compared to that of mixed integer programming (MIP). In the LP model, presented in an earlier paper, a linear objective function was used as a surrogate for the actual objective function, which is intrinsically nonlinear. In the LP model, transportation costs were determined per seedling, whereas in the MIP model they were based on vehicle loads. When the number of transported seedlings within a certain period decreased, for instance, due to planting through the growth period, the computational accuracy of the LP model was clearly lower than that of the MIP model. Despite that, differences in allocation of orders between these two models were small. Thus, in the actual business situation of Finnish nursery companies, standard LP seems to be an adequate tool for management of seedling transportation. From the standpoint of cost-efficient seedling business, planting through the growth period increased optimal transportation costs markedly. In addition to the seedling business, these results can be utilized in other types of business dealing with analogous transportation problems.

Use of pesticides in Finnish forest nurseries in 1996

In 1996 a questionnaire on seedling production and use of pesticides was sent to 33 forest nurseries in Finland. Twenty-eight nurseries answered the questionnaire; thus the survey covered about 80% of the Finnish production of forest seedlings. According to this study, the Finnish nurseries together are using about 1000 kilograms of pesticides (as active ingredient, a.i.) annually. The most used herbicide was terbutylazine (Gardoprim-Neste®), and half of the total amount of fungicide used was chlorothalonil (Bravo 500®). Three fourths of the insecticide products had permethrin as the active ingredient. The nurseries applied, on average, 1.7 kg pesticides (a.i.)/ha annually, although the amount varied considerably between nurseries. In production of container seedlings the highest mean amounts of pesticides were applied to pine seedlings (9.5 kg/ha) and the lowest to spruce seedlings (0.9 kg/ha). To the fields of bareroot seedlings the nurseries applied, on average, 3.9 kg pesticides (a.i.)/ha. Mean amounts of pesticide (a.i.) per 1000 seedlings grown in containers were almost the same for birch and pine production, 1.6 and 1.7 grams, respectively; for production of spruce seedlings the comparable values were less than 0.5 grams. For production of bareroot seedlings the nurseries used about four times more pesticides than for container seedlings.

Fertilization practice in Finnish forest nurseries from the standpoint of environmental impact

In 1996 a questionnaire concerning actualsystems and practices used in production ofseedlings was sent to 33 Finnish forestnurseries. A total of 28 nurseries answered thequestionnaire. These replies represented about80% of the total production of forestseedlings in Finland. The nurseries used about200 metric tons of fertilizers in 1996, whichwas about 25% of the fertilizer use in 1976.Explanations for the decrease in fertilizationare the shift from bareroot production tocontainer production and the decrease in totalproduction from 190 to 150 million seedlings.Finnish nurseries applied about 100 mg N and50 mg P per container seedling shipped, and820 mg N and 240 mg P per bareroot seedling.The mean annual applications of N and P in 1996were about 180 kg/ha and 90 kg/ha for containerstock and 130 kg N/ha and 40 kg P/ha forbareroot stock. However, the variation betweennurseries was large.

Variation in the electrical conductivity and acidity of preculture peat growth media used in Finnish tree nurseries

The uniformity of lime and fertilizer incorporated into commercial peat growth media was studied before these media were used for culturing of seedlings. Uniformity was estimated by measuring the acidity (pH) and electrical conductivity (EC) in water suspensions of peat samples (1 : 2.5, v/v) after the samples had soaked for 1 day and 7 days. The mean pH of the fertilized peat media was 4.5–4.8 and 4.6–5.1, and the mean EC was 0.32–0.35 and 0.43–0.49 mS cm−1 after 1 and 7 days soaking, respectively. For both pH and EC, significant differences were found between peat media, although the practical importance of these differences was considered to be small. The variation in acidity of peat media within greenhouses was also rather small. The large variation in EC suggests possible heterogeneity in the growth of seedlings grown in these media due to the effects of this variation on availability of water and nutrients.

Conifer seedling root fungi and root dieback in Finnish nurseries

Fungi were isolated from the roots and growth substrate of bare‐rooted and containerized Pinus sylvestris and Picea abies nursery seedlings displaying a root dieback. Isolations were also made from visually healthy seedlings. The potential pathogenicity of all isolated species was determined in laboratory trials. Cylindrocarpon spp., Fusarium spp. and Trichoderma viride were frequently isolated. The isolation frequency of a uninucleate Rhizoctonia‐like fungus, Pythium spp. and Phytophthora imdulatum from diseased containerized seedlings and their pathogenicity in tests suggest that these fungi are likely involved in the root dieback disease in containers. The pathogenic Rhizoctonia‐like fungus in addition to Pythium spp. was also isolated from bare‐rooted seedlings. In greenhouse tests Pythium spp. were more pathogenic to 4‐week‐old Scots pine seedlings grown before transplantation in unsterile substrate than to those seedlings grown axenically in agar. External factors are considered to have some role in the expression of disease.

Height variation of transplanted seedlings of Scots pine in Finnish nurseries

The height variation of Scots pine (Pinus sylvestris L.) seedling stock was studied using data from annual inventories of seedling crops. The heights of 240 batches of 2-year-old and 3-year-old transplanted seedling from the years 1973–1986 grown at three nurseries in southern Finland were examined. From each batch, 100 clusters of three successive seedlings were systematically located and measured. The mean heights of the seedling batches ranged from 7.8 to 27.0 cm, with a mean of 14.1 cm. Within batch standard deviations ranged from 1.7 to 7.8 cm, with a mean standard deviation of 3.7 cm. There was considerable variation in the mean heights of seedling batches both within a given year and between years. However, estimated variance components of seedling height showed that year, batch and cluster effect each accounted for about 20 percent of the total variance, while seedling effect explained the remaining 40 percent. The implications of results for single tree and batch grading are discussed.

Frost resistance and frost damage in pinus sylvestris seedlings during shoot elongation

No differences were found in the frost resistance of the different‐aged (2–7 weeks) germlings of Scots pine. The critical temperature was ‐6°C to —3°C. A temperature of ‐4°C killed half of the germlings and produced damage in one fifth of the surviving seedlings; the needles turned brown and growth ceased. The frost resistance of the previous year's shoots of two‐year‐old seedlings, measured by the impedance method, decreased during the shoot elongation period from — 10°C to — 4°C. Damage to the current shoots during shoot elongation appeared as deformation and discolouration of the needles and abnormal development or death of the apical bud. The results indicate that frost is not the cause of growth disturbances observed in Finnish nurseries.

The appearance of soil-borne viruses in Finnish plant nurseries II

In the beginning of the 1970’s, the occurrence of soil-borne viruses in 30 Finnish nurseries and experimental fields of garden plants at 3 research stations was mapped. Viruses were isolated on 26.9 % of the 672 plant and soil samples collected. The two most commonly found viruses were tobacco necrosis virus (TNV), 42.5 %, and tobacco rattle virus (TRV), 23.7 %. Tomato black ring virus (TBRV) and raspberry ringspot virus (RRSV) were isolated for the first time in Finland. The abundant occurence of TBRV in 32 samples was due to the abundance of Phlox paniculata samples. RRSV was isolated from only a few samples. The vectors of all of the above-mentioned viruses were found in many samples. The fungus vector of TNV, Olpidium brassicae, was investigated by examining the roots microscopically. The vector of TRV, the Trichodorus sp. nematodes, and the vector of TBRV and RRSV, the Longidorus sp. nematodes, were isolated from soil samples. In addition to the foregoing, tobacco mosaic virus was isolated from 31 samples of 6 nurseries and 2 experimental fields. Viruses were isolated from many weed samples, especially from roots of Senecio vulgaris and Stellaria media. Perennials proved to be virotic. All of the above mentioned viruses, especially TBRV and TRV, were isolated from Phlox paniculata; TBRV was also found in an Astilbe x arendsii sample. Dicentra spectabilis, like Phlox, was commonly infected with TRV. No clear results could be obtained from control experiments.

Ultrastructural aberrations referring to viruses in the needles of young growth disturbed pine seedlings

AbstractUltrastructural abnormalities in phloem albuminous cells of needles of young pine seedlings from two Finnish nurseries suffering from the growth disturbances of conifer seedlings were studied. Needle samples were taken from growth disturbed seedlings and from healthy looking nursery seedlings as well as from naturally born forest seedlings. The results are discussed in relation to the possibility of virus disease in growth disturbed seedlings. The first trials to observe the viruslike particles from abnormal seedlings will be discussed, too.