Über die Grundlagen der Entstehung und Begegnung von Insekten-Massenvermehrungen im Wald

Zusammenfassung Die fundamentale Ursache der Forstinsekten-Massenvermehrungen besteht darin, daß die heutigen Kunstforsten naturfern sind und kein stabiles ökologisches Gleichgewicht mehr besitzen. Beim Zusammentreffen von Wärme und Trockenheit kommt es zu Massenvermehrungen, wobei die Wasserhaushaltsstörungen im Baum die Hauptrolle spielen. Sie senken die Harzungskraft als Mittel der Abwehr von Borkenkäfern, und sie fördern die Blattfresser durch Verbesserung der Nahrungsqualität (Erhöhung des Zuckergehalts).Bezüglich der Gegenmaßnahmen ist zu berücksichtigen, daß Borkenkäfer sekundär sind und bleiben. Die einzig wirksame Bekämpfung ist hier die Entfernung des stark von Käfern befallenen Holzes aus dem Wald. Bei den Blattfressern besteht ein grundsätzlicher Unterschied zwischen Laub- und Nadelbaumschädlingen. Die Laubbäume haben ein großes Regenerationsvermögen und sterben auch nach mehrmaligem Kahlfraß nicht ab. Bei den Nadelbäumen bedeutet teils ein einmaliger, teils ein zweimaliger Kahlfraß den Tod des Waldes.Der Waldbau hat durch Umwandlung der Naturwälder in Kunstforsten das Schädlingsproblem geschaffen. Die Ausbringung breitenwirksamer Pestizide führt zu immer häufigeren und stärkeren Schädlingsvermehrungen. Die Situation verschärft sich eklatant durch eine im Gang befindliche Klimaverschiebung in Richtung zu mehr Wärme, Trockenheit und Stürmen. Nur die Rückkehr zu naturnahen Wäldern kann das Forstschädlingsproblem lösen. Die heutige ökonomische Forstwirtschaft muß zu einer ökologischen Waldwirtschaft werden.

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On the fundamentals of forest insect outbreaks and of counter measures

The forest insects outbreaks finally are founded on the transformating natural woods into artificial forests with destable ecological equilibrium. High temperatures in combination with dryness lead to insect outbreaks beginning with the break down of the watere-quilibrium in the trees. By this the resin- and sappressure drops allowing bark beetles to enter the trees — and the food quality for caterpillars (sugar contents of foliage) arises increasing the fecundity.Relating to the counter-measures it should be considered that bark beetles are secondary and remain so. The only effective control consists in taking out all the strongly infested wood. In regard to foliar feeding insects there is a fundamental difference between deciduous trees and conifers: the former have high ability for regenerating and so they survive several complete defoliations whereas the latter die after one defoliation caused by early feeders or two defoliations caused by late feeding pests.The forest builder has created the pest-problem by transforming natural woods into artificial forests. The using of broadly acting pesticides results in new outbreaks with worse consequences. The situation is intensified by a present changing of climate in tendency to more heat and dryness and storms. Only by going back to natural woods it will be possible to overcome the wood pests problem. The present economical forestry has to make way for a ecological wood cultivation.

     

Contribution of chickpea nitrogen fixation to increased wheat production and soil organic fertility in rain-fed cropping

Nitrogen balances, i.e. the difference between N ₂ fixation inputs and N in harvested products (outputs), and rotational benefits of chickpea ( Cicer arietinum) on soil organic fertility and wheat ( Triticum aestivum) yields were quantified for rain-fed systems in the northern Punjab, Pakistan. The experiments were conducted during 1995–2000 at three sites. The four treatments were continuous wheat (0 N), continuous wheat (+N), chickpea-wheat (0 N) and chickpea-wheat (+N). The +N fertiliser rate was 100 kg N ha ^-1 applied to the wheat. Grain yields of the wheat with 0 N varied in the range 1.0–3.0 t ha ^-1, compared with 2.0–3.2 t ha ^-1 for the N-fertilised wheat. Chickpea grain yields were in the range 0.6–2.0 t ha ^-1. Chickpea N ₂ fixation was assessed using the natural ¹⁵N abundance method. Percentage of chickpea N derived from N ₂ fixation (%Ndfa) estimates were 58% (Mandra), 65% (Taxila) and 86% (Islamabad). The overall mean %Ndfa was 78%. Crop N fixed by the chickpea varied between sites (87–186 kg N ha ^-1) and essentially reflected crop biomass. The overall mean N balance for chickpea (crop N fixed minus N removed in grain and above-ground residues) was +28 kg N ha ^-1. Wheat grain yields responded to chickpea (19–73% increase for the three sites), to fertiliser N (99–136% increase) and to the combination of chickpea and fertiliser N (106–145% increase). Chickpea in the rotation increased soil organic C by 30% and soil N by 38%, relative to the continuous wheat with 0 N. These experiments indicated that chickpea could have a positive N balance, even when shoot residues were removed, and confirmed the rotational benefits of chickpea for improving soil organic fertility and yield of a following wheat crop.     

What soil information do crop advisors use to develop nitrogen fertilizer recommendations for grain growers in New South Wales,Australia?

The Australian grains industry relies on mineralized nitrogen (N) from soil organic matter and plant residues, but fertilizer N is increasingly needed to optimize yields. Most farmers are guided on N fertilizer requirements by commercial crop advisors. We surveyed (n = 132) and interviewed (n = 11) New South Wales grains advisors to gauge the usage of soil process understanding, soil data and decision support systems (DSSs) when developing N recommendations. Soil moisture at sowing, seasonal forecasts, crop rotation, soil mineral N, financial risk profiles and paddock history were all used to prepare N fertilizer advice, but stored soil moisture was most important. Farmer confidence in soil N testing was low due to high spatial variability. Most advisors calculated N fertilizer required for yields within 10%–15% of crop potential, but clients’ attitude to financial risk guided final N recommendations. Conservative growers preferred a low input system, while more reliable rainfall or greater reliance on stored soil water led growers to apply higher N rates to maximize long‐term profits. Advisors preferred “rules‐of‐thumb,” simple DSSs and knowledge of crop growth, to elaborate DSSs requiring detailed inputs and soil characterization. Few used in‐crop N sensing. N decision methodologies need to be updated to account for changes in soil fertility, cropping systems and farming practices. New research is needed to answer practical questions regarding soil N mineralization and N losses associated with alternative N application practices and extreme weather events. Training of new advisors in N processes and DSS use needs to be ongoing.     

III. Buchbesprechungen

Ohne Zusammenfassung     

III. Buchbesprechungen

Ohne Zusammenfassung     

III. Buchbesprechungen

Ohne Zusammenfassung     

Buchbesprechungen

Ohne Zusammenfassung     

Begleitinsekten in Buchdrucker-Pheromonfallen in Südtirol

Results are given on insects catched by 30 traps baited with Pheroprax in July and August 1984 in South Tyrol. In addition to 116,000 indiv. ofIps typographus the flight barriere traps contained 12,000 indiv. of other bark beetle species and 1222 indiv. of other insects belonging to 8 orders, 57 families and 150 species. Most dominant were Coleoptera (869=71% indiv.) followed by Hymenoptera (302=25%). With 211 indiv. (17%) the Honey bee,Apis mellifera, showed a surprising high quota.     

Über die Rolle des Häutungshemmstoffes Dimilin im Waldschutz und Waldökosystem

Zusammenfassung Der Häutungshemmstoff Dimilin hat sich im Waldschutz gegen freifressende Schmetterlings- und Blattwespenlarven hervorragend bewährt. Gegen saugende und versteckt fressende Gliederfüßler ist er unwirksam. Er gehört keiner Giftklasse an, ist nicht phytotoxisch und ist bienenungefährlich. Auch ein Teil der Wurzelnematoden kann mit ihm bekämpft werden.Bei phytophagen Insekten-Imagines kann Dimilin zur Verminderung der Reproduktionsrate führen. Gegen frisch abgelegte Arthropoden-Eier wirkt Dimilin ovizid.Den zahlreichen positiven Eigenschaften des Dimilins stehen als unerwünschte Nebenwirkungen vor allem seine Persistenz sowie die Häutungshemmung auch bei indifferenten phytophagen Larven gegenüber. Ob und wieweit unter normalen Bekämpfungsbedingungen Teile der Bodenfauna durch Dimilin beeinträchtigt werden, müssen künftige Untersuchungen zeigen. Die Wahrscheinlichkeit hierzu ist sehr gering.

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On the role of Dimilin a new insecticide inhibiting the chitin synthesis in forest protection and wood ecosystems

In last years Dimilin showed high efficiency against free feeding larvac of Lepidoptera and Tenthredinidae injurious to forests. Arthropods sucking plant sap or living hidden at plants can not be reached by this substance. However some species of nematodes living ectoparasitic on roots are susceptible. Dimilin does'nt belong to a poison-class. It is'nt toxic to plants and to bees.Adult insects are influenced by Dimilin in the direction of decreasing the reproduction. The substance is ovicide against fresh laid insect eggs.Some side effects of Dimilin injuring the ecosystem are the long termed persistence and the destroying of phytophagous larvae which are economic indifferent. Further studies must show wether the soil fauna is affected by control measures using Dimilin.