First report of barley yellow dwarf luteovirus onMiscanthus in the United Kingdom

Barley yellow dwarf luteovirus (BYDV) was detected in field grownMiscanthus sacchariflorus propagated from root cuttings. Inoculation of BYDV toM. sinensis plants grown from seed had an adverse effect on shoot growth and leaf development.     

Recent advances in the biological control of fusarium wilts

Studies of soils suppressive to fusarium wilts have indicated that the phenomenon is fundamentally microbiological in nature, resulting from complex microbial interactions between the pathogen and all, or a part of, the saprophytic microflora. Many groups of micro-organisms have been proposed as having a role in this process. The most consistent results show that non-pathogenic Fusarium oxysporum and fluorescent pseudomonads are the main agents for biological control. Each group has been effective in reducing the severity of fusarium diseases in several crops under experimental conditions. All the problems associated with application of antagonists have not yet been solved, but special situations exist where biological control could be applied soon. In Europe, the present development of soil-less systems to grow tomatoes, cucumbers, carnations and a few other species of flowers and vegetables in greenhouses, offers a unique opportunity to use antagonists. A strain of non-pathogenic Fusarium isolated from soil from Chǎteaurenard can be established in the soil-less substrates, or in the potting mixtures, before transplanting the plants and in these conditions can prevent colonization of the substrates by the pathogens. It gave good control of fusarium wilts of tomatoes, carnations and cyclamens, and of crown and root rot of tomatoes due to F. oxysporum f.sp.radicis lycopersici. This non-pathogenic strain, produced by liquid fermentation and mixed with talc, is easy to introduce into soil-less substrates after having been suspended in water or in liquid fertilizer. Experiments have been under way in commercial greenhouses for several years, but it will be necessary to wait at least two more years to complete all the tests required for the registration of the product as a biopesticide. Similar experiments have been conducted with a strain of fluorescent pseudo-monad also isolated from the soil of Chǎteaurenard, which shows poor antagonistic effect when applied alone but consistently improves disease control when applied in combination with the non-pathogenic Fusarium. In fact, application of both antagonists together always gave total control of the diseases, the yield in the treated plots being equal to that in the healthy control. These experiments show that combining antagonists can improve the consistency of biological control.     

The Viability of Metapopulations: Individual Dispersal Behaviour Matters

Metapopulation models are frequently used for analysing species–landscape interactions and their effect on structure and dynamic of populations in fragmented landscapes. They especially support a better understanding of the viability of metapopulations. In such models, the processes determining metapopulation viability are often modelled in a simple way. Animals’ dispersal between habitat fragments is mostly taken into account by using a simple dispersal function that assumes the underlying process of dispersal to be random movement. Species-specific dispersal behaviour such as a systematic search for habitat patches is likely to influence the viability of a metapopulation. Using a model for metapopulation viability analysis, we investigate whether such specific dispersal behaviour affects the predictions of ranking orders among alternative landscape configurations rated regarding their ability to carry viable metapopulations. To incorporate dispersal behaviour in the model, we use a submodel for the colonisation rates which allows different movement patterns to be considered (uncorrelated random walk, correlated random walk with various degrees of correlation, and loops). For each movement pattern, the landscape order is determined by comparing the resulting mean metapopulation lifetime T_m of different landscape configurations. Results show that landscape orders can change considerably between different movement patterns. We analyse whether and under what circumstances dispersal behaviour influences the ranking orders of landscapes. We find that the ‘competition between patches for migrants’ – i.e. the fact that dispersers immigrating into one patch are not longer available as colonisers for other patches – is an important factor driving the change in landscape ranks. The implications of our results for metapopulation modelling, planning and conservation are discussed.     

Winter embolism,mechanisms of xylem hydraulic conductivity recovery and springtime growth patterns in walnut and peach trees

Xylem vessels of Prunus persica Batsch (peach) and Juglans regia L. (walnut) are vulnerable to frost-induced embolism. In peach, xylem embolism increased progressively over the winter, reaching a maximum of 85% loss of hydraulic conductivity (PLC) in early March. Over winter, PLC in walnut approached 100%, but the degree of xylem embolism varied during the winter, reflecting the ability of walnut to generate positive xylem pressures in winter and spring. In contrast, positive xylem pressures were not observed in peach. Controlled freeze-thaw experiments showed that frost alone is insufficient to increase embolism in peach; evaporative conditions during thawing are also required. However, when both species were protected from frost, PLC was zero. At bud break, there was complete recovery from embolism in walnut, whereas PLC remained high in peach. Three mechanisms responsible for the restoration of branch hydraulic conductivity were identified in walnut: the development of stem pressure, the development of root pressure and the formation of a new ring of functional xylem, whereas only one mechanism was observed in peach (new functional ring). The climatic conditions necessary for the manifestation of these mechanisms were investigated.     

Which grow better under the canopy of Norway spruce planted or sown seedlings of European beech?

Direct seeding and planting of European beech (Fagus sylvaticaL.) are two common techniques for the conversion of pure Norwayspruce (Picea abies [L.] Karst.) stands into mixed stands. Thisstudy tested whether the growth of sown beech seedlings differsfrom that of planted seedlings of two stock types. Thereforeat two experimental sites repeated measurements were made ofheight, stem and first order branch diameter on sown and plantedseedlings over a period of nine years. The results showed thatthe growth responses of planted and sown seedlings to the environmentalconditions below the canopy of overstorey Norway spruce wererather similar. No differences between planted and sown seedlingswere found in their diameter and their estimated abovegrounddry weight. For all three batches the ratio between the estimatedbranch dry weight and the estimated main stem dry weight (branch-shoot-ratio(BSR)) was increased with age. Due to intraspecific competitionBSR was lowest for the sown seedlings irrespective of theirage. Differences in growth dynamics between planted and sownseedlings were found. For example, differences in the heightor the estimated aboveground woody dry weight between sown andplanted seedlings at a given age were not constant. Height,diameter and estimated dry mass of the seedlings in relationto age could be modelled precisely by a second-order polynomialfunction in the hitherto studied period.     

Versuche mit Toxaphen-Staub zur Festsfellung der Bienengefährlichkeit und der Wirkung gegen Kohlschotenrüßler und Rapsglanzkäferler und Rapsglanzkäfer

Zusammenfassung Es wurden Versuche zur Kl?rung der Bienenungef?hrlichkeit und der Wirkung des Kontaktinsektizids Toxaphen angelegt. In orientierenden Laborversuchen konnte eine 100% ige Abt?tung von Kohlschotenrü?lern und Rapsglanzk?fern auch mit der H?lfte der normalen Aufwandmenge (20 kg/ha) erreicht werden. In Freilandversuchen waren die Abt?tungsziffern beider genannten Sch?dlinge als befriedigend bis gut zu beurteilen. Bienenverluste traten troB St?ubung w?hrend des Bienenfluges nicht ein. VorausseBung für den Erfolg scheint nach den bisherigen Feststellungen eine Trockenperiode von mindestens 8 bis 10 Stunden zu sein, da das Mittel eine geringere Anfangswirkung besiBt. Weitere Versuche sind geplant.     

Durability of thermally modified timber from industrial-scale processes in different use classes: Results from laboratory and field tests

Material from four common European processes of industrial heat treatment of timber was examined comparatively with reference to biological laboratory standard tests and field tests in soil contact and above ground. The thermally modified timber (TMT) used in the study was: Plato wood from the Netherlands, ThermoWood from Finland, New Option Wood (NOW) from France, and oil-heat-treated wood (OHT) produced in Germany. Tests of resistance to basidiomycetes (EN 113, 1996) and tests of resistance to soft rotting microfungi and other soil-inhabiting microorganisms (EN 807, 1997) showed substantially lower mass losses of TMT compared with controls. Only slight differences in mass loss were found between the four thermally modified materials. Based on results from laboratory standard tests all tested heat-treated materials were classified as durable to moderately durable [durability class (DC) 2-4], analogous to the classification of natural durability (EN 350-1, 1994). In contrast, the classification of TMT samples after 5.5 years' exposure in soil contact, in accordance with EN 252 (1990), was slightly durable to not durable (DC 4-5), whereas the classification obtained after 5.5 years' exposure in double layers in European hazard class (EHC) 3 (EN 335-1, 1992) was very durable to moderately durable (DC 1-3). On the basis of 5.5 years' field testing, thermally modified material (independent of the treatment process and supplier) appears not to be suitable for in-ground contact application. However, the suitability of TMT for use out of ground in EHC 3 was ascertained and is recommended.     

Decay-influencing factors: A basis for service life prediction of wood and wood-based products

The need for a reliable database and a corresponding methodology to predict service life of wood and wood-based products emanates from the European Construction Products Directive, as well as from a strong interest by the building industry. A literature review on decay-influencing factors and on previous approaches to implement methods and tools for service life estimations was the basis for a concept for service life prediction of wooden components. The effect of various indirect decay factors was found to be reducible to a few direct decay factors, with material resistance, as well as wood moisture content, wood temperature and their dynamics among the key factors for fungal decay. Approaches that consider only indirect factors, e.g. climate indices, suffer from poor correlation with service life or decay rates. Therefore, the overall consideration of all possible influences, reduced on the key direct decay factors in first instance, is recommended. To fill a theoretical model with a reliable database, various data sources need to be considered, in decreasing order of priority: in-service performance, field test data, laboratory test data, survey analysis and expert opinion.