Increase in the content of nitrogenous compounds at lumber surfaces during drying and possible biological effects

Summary Nitrogen contents have been determined at different depths from the surface of dried pine (Pinus sylvestris) and spruce (Picea abies) lumber. The effects of factors such as time of felling, storage of the timber, and drying process for the lumber, have been studied. Part of the selected lumber was characterized by surfaces which were yellowish after drying. At such surfaces, to a depth of about 2 mm, a high accumulation of nitrogen was always found. Yellowing is enhanced in lumber from wet-stored timber but also occurs in other lumber. Some possible contributive factors are suggested. More research in this field is proposed. The nitrogen gradients in outer sapwood without a yellow surface and in inner sapwood and in heartwood were much weaker. The effect which enrichment of nitrogenous compounds at surfaces may have on timber with regard to its disposition towards moulding is discussed. Although attention is drawn to the fact that strong nutrient gradients may occur, it must be emphasised that in most lumber nutrient gradients are weak and probably without practical consequence for its susceptibility towards fungal attack.     

Untersuchungen zur Wirkung eines Kernpolyedervirus ausNeodiprion sertifer (Geoffr.) auf andere Blattwespenarten

A virus strain of the European pine sawfly (Neodiprion sertifer [Geoffr.]) NsNPV was tested against 7 species of sawflies. This strain was pathogenic forN. sertifer, M. pallipes andD. pini. After infection, retardation of the growth of the larvae and high mortality were observed. The speciesD. similis, G. laricis, P. abietina andC. abietis didn't show any susceptibility. The virus formed inclusion bodies in the midgut-cells of theN. sertifer-larvae; no polyhedra could be detected in dead larvae ofM. pallipes andD. pini. Extracts of infected larvae of these two species applicated toN. sertifer caused a typical polyhedrosis again.     

Chemical and physical changes required for producing dimensionally stable wood-based composites

Summary The springback of compressed wood caused by built-up internal stresses results in excessive thickness swelling of wood-based composites when exposed to moisture. Steam pretreatment can cause partial hydrolysis of hemicellulose for both hardwoods and softwoods which markedly increases the compressibility of wood and in turn significantly reduces the build-up of internal stresses in composites during hot pressing. This steam pretreatment process is a very effective method for producing dimensionally stable wood-based composites. Mild steam pretreatments (e.g. 3 to 4 min at 1.55 MPa) cause a significant reduction of the water insoluble xylan content in hardwoods and the amount of xylan, mannan and galactan in softwoods without any apparent changes in the cellulose or lignin content.The authors wish to thank G. Bastien and B. S. Lethbridge for technical assistance. W. Schwald is grateful to the Fonds zur Förderung der wissenschaftlichen Forschung, Vienna, Austria for granting an Erwin-Schrödinger scholarship (Proj. No. J0128C)     

Gradation der Nonne (Lymantria monacha L.) in Polen von 1978 bis 1984

Zusammenfassung Berichtet wird in Einzelheiten über die Nonnenkalamität, die zwischen 1978 und 1984 in Polen Bekämpfungsmaßnahmen auf insgesamt mehr als 6,3 Mill. ha notwendig machte und damit eine der schwersten bekannten Katastrophen dieser Art überhaupt darstellt.Ausbruch und Fortgang der Kalamität werden im einzelnen geschildert. Betroffen waren ganz überwiegend (zu rd. 80% der Befallsfläche) Kiefern-Reinbestände aller Altersklassen, erst mit Abstand—und im fortgeschrittenen Stadium der Kalamität—folgten Mischbestände und reine Fichte. Die Mechanismen zur Selbstregulation durch Antagonisten kamen offenbar erst spät in Gang und hatten angesichts der weiten Verbreitung sehr hoher Schädlingsdichten keine erkennbare Wirkung.Technische Einzelheiten werden über die Nonnen-Prognose unter den gegebenen Bedingungen berichtet, sowie über die Bekämpfungsmaßnahmen. Erfolgreich eingesetzt wurden vor allem Pyrethroide verschiedener Herkunft. Die Ausbringung erfolgte überwiegend mit Luftfahrzeugen. Auf dem Höhepunkt der Kalamität 1982 waren 159 Flugzeuge und 23 Hubschrauber im Einsatz.Schließlich werden einige Beobachtungen über die Erholung geschädigter Bestände mitgeteilt. Totalverluste—vor allem an Fichte—beschränkten sich auf den erstaunlich geringen Anteil von rd. 0,5% der Gesamtschadfläche.

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Outbreak of Nun Moth (Lymantria monacha L.) in Poland between 1978 and 1984

The paper reports details on the outbreak of Nun Moth (Lymantria monacha L.) in Poland during 1978/1984. Chemical control was necessary on more than 6.3 mill. ha making this outbreak one of the most serious ever noticed.Start and expansion of the outbreak are described in detail. Above all pure stands of Scots pine were affected (80% of the infestation area), only during the advanced stages of the out-break followed by mixed stands and pure Norway spruce.Mechanisms of self regulation by antagonists started obviously late and produced no visible effect upon the wide spread high densities of the pest.Technical details are reported about the Nun Moth survey and control measures in Poland. Pyrethroids of various sources proved to be most successful chemicals for control. The applications were mainly made by air. On the peak of the outbreak in 1982 159 airplanes and 23 helicopters were in action.Finally some observations on the regeneration of damaged stands are reporeted. Total losses—mainly of Norway spruce —were found to be of surprising low dimensions (about 0.5% of the infestation area).

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Mit einer Abbildung und einer Tabelle     

Über Borkenkäfer (Col., Scolytidae) in Zweigen der Zirbe (Pinus cembra) in Südtirol

In dead twigs ofPinus cembra taken from two localities above 2000 m in South Tyrol in 1984Pityogenes bistridentatus, three species ofPityophthorus (henscheli, knoteki, pityographus) and one species ofIps (amitinus) were found. Informations are given on taxonomy, host preference and bionomy of these bark beetles.     

Antagonismus in vivo von fluoreszierenden Pseudomonaden gegenüber Rhizoctonia solani und Pythium aphanidermatum an Gurken und Buschbohnen

Zusammenfassung Fluoreszierende Pseudomonaden, die sich als Antagonistenin vitro gegenüberRhizoctonia solani undPythium aphanidermatum erwiesen haben, wurden an Gurken und Bohnen auf Antagonismusin vivo untersucht. Die Effizienz der Antagonisten in Auflaufversuchen gegenüberR. solani war niedriger als beiP. aphanidermatum. Die besten Isolate konnten in mitR. solani verseuchter Erde Auflaufraten von 30–40% erzielen, gegenüberP. aphanidermatum dagegen 40–60%. Die Wirkung der Antagonisten zur Verhütung von Spätinfektionen der Pflanzen war deutlich besser. So konnten 16 Isolate eine Schädigung durchR. solani an Bohnen zwischen 90 und 100% reduzieren. An Gurken konnten 12 Isolate eine Schädigung durchP. aphanidermatum auf 70–80% reduzieren.

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Fluorescent pseudomonads, which showed antagonism in vitro against Rhizoctonia solani and Pythium aphanidermatum, were investigated for antagonism in vivo using bean and cucumber. The efficiency of the antagonists in germination tests against Rhizoctonia solani was lower than against Pythium aphanidermatum. In soil infected with Rhizoctonia solani the germination rates of the seeds remained between 30 and 40%, whereas against Phytium aphanidermatum some Pseudomonas-strains caused germination rates of 40–60%. The preventive effect of the antagonists against fungal infection after the germination was better. 16 isolates reduced the damage caused by Rhizoctonia solani to bean between 90 and 100%. Damage caused by Pythium aphanidermatum to cucumber was reduced by 12 antagonists between 70 and 80%.

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Mit 4 Abbildungen     

High-yield pulping of aspen wood: Relation between pulp properties and fibre characteristics by multiple linear regression

Summary High-yield pulps have been obtained by means of steam explosion pulping. This process was carried out as follows: 1) chips soak impregnation (60 °C, 24 h, L/C = 6) in solutions containing 8% Na₂SO₃ and a variable concentration of either Na₂CO₃ or NaHCO₃, ranging from 0 to 2%; 2) cooking at high temperature (190–200 °C) for short time (2-1 min); 3) rapid pressure release. This work shows that mechanical properties were substantially improved when adding a second chemical to the Na₂SO₃ impregnation solution. Moreover, refining energy requirement was significantly reduced. However, the higher chemical charge used made the optical properties drop. In this paper, mathematical models have been proposed in order to accurately predict specific refining energy and paper properties from sulfonate content and pulp yield. In addition, the relative importance of these two parameters has been studied.Thanks are due to the Natural Science and Engineering Council of Canada (NSERC) and Fonds pour la Formation de chercheurs et l'aide à la recherche of Quebec (FCAR) for their financial support.