Integrierter Pflanzenschutz im Obstbau

Zusammenfassung Auch wenn die Voraussetzungen für eine ideale integrierte Sch?dlingsbek?mpfung noch nicht erfüllt sind, kann diese Methode im Obstbau schon mit gutem Erfolg angewendet werden. Das wird an einigen Beispielen aus der Praxis erl?utert. Rund die H?lfte der sonst üblichen Insektizidbehandlungen wird eingespart, wenn bei den Empfehlungen an die Obstbauern die wirtschaftlichen Schadensschwellen berücksichtigt werden. Dazu ist allerdings notwendig, die einzelnen Obstanlagen zu überwachen. Für die Obstbauern ist an der integrierten Bek?mpfung zun?chst die Senkung der Produktionskosten von Interesse, weniger die schwerer zu erkennenden Vorteile auf biologischem Gebiet, die sich jedoch im Lauf der Zeit noch st?rker auf die Produktionskosten auswirken werden als die sich schon unmittelbar auswirkende Einsparung von Spritzungen.

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Summary In spite of the fact that all conditions for an ideal integrated pest control system are not yet fulfilled, this system has been applied already in fruitgrowing with good results. This is demonstrated with some results obtained in commercial orchards. About half of the normally applied number of insecticidal treatments were found to be unnecessary, provided that the economic injury levels were regarded. It is therefore of vital importance to inspect the orchards individually. For commercial growers the reduction of production costs is most interesting; the biological consequencies are more difficult to estimate although it may be expected that in the long run they will have a strong reducing effect on the production costs by reducing the costs of the insecticidal treatments.

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Résumé Même si les conditions pour une lutte integrée idéale ne sont pas encore remplies, cette méthode peut déjà être appliquée avec succès en arboriculture. Cette affirmation est illustrée par quelques exemples tirés de la pratique. A peu près la moitié des traitements usuels est économisée, si l'on tient compte des seuils de tolérance économiques dans les conseils donnés aux arboriculteurs. A cet effet, il est cependant nécessaire de surveiller chaque plantation. Ce qui intéresse surtout l'arboriculteur, ce sont les possibilités de diminution des frais de production qu'offre la lutte integrée, bien plus que les avantages biologiques difficilement perceptibles. A la longue, ceux-ci auront cependant un effet encore plus marqué sur les économies de traitements réalisables dans l'immédiat.

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mit Unterstützung durch die Deutsche Forschungsgemeinschaft     

Variation in seedling hydraulic architecture as a function of species and environment

Northern red oak (Quercus rubra L.) and yellow-poplar (Liriodendron tulipifera L.) were grown for two years in full sunlight (unshaded) or 20% of full sunlight (shaded) under either well-watered or drought conditions. There was a close association between evaporative flux (in situ) and leaf-specific conductivity (LSC) in stem segments of both species. Shaded, drought-stressed seedlings of both species had significantly reduced leaf area, evaporative flux, volume flow rate in xylem, flow velocity, potentially functional xylem area, and LSC than unshaded, well-watered seedlings. Reductions in LSC associated with drought or shade were similar for both species; and within a treatment, both species had similar LSC. Species differed in the manner of LSC adjustment to drought and shade. Reductions in leaf area associated with drought or shade were accompanied primarily by reductions in potentially functional xylem area for L. tulipifera, and by reductions in flow velocity for Q. rubra. These results suggest (1) the existence of a homeostatic balance between evaporative flux and LSC, (2) that species with widely different growth patterns and xylem anatomies may develop similar LSC within the same environment, and (3) a possible hydraulic basis for differences in habitat between ring- and diffuse-porous species.     

Wettability of four Asian meranti species

Summary The wettability of four Asian meranti species (dark red, light red, white, and yellow) in various liquids was studied by a cone-immersion technique. Wettability was expressed in terms of the area under the force-immersion curve and referred to as the wettability index. Wettability was strongly influenced by the pH of the solution, generally increasing with increasing pH. Surfactant type affected wettability, with the cationic type yielding the greatest wettability followed by anionic and nonionic types. Among the liquids used, distilled water gave the lowest, and acetone-isopropyl alcohol solution gave the greatest wettability. Of the meranti species, yellow meranti showed the greatest wettability, followed by white, light red, and dark red meranti.A plot of the relative amount of liquid absorbed into the wood sample versus wettability index yielded two regions, one attributed mainly to liquid trapped in crevices on the wood surface, and another which may be more indicative of wood-liquid interactions. A highly significant linear correlation between wettability index and liquid surface tension was found for those species with low and medium wettability, while that with high wettability showed no correlation. A new empirical approach of determining the critical surface tension of wood is discussed. Limited data for the present method indicated close agreement with result from the literature obtained by the use of the well-known Zisman's contact angle approach.