Experimentelle Infektion von Pityogenes chalcographus L. (Coleoptera,Scolytidae) durch Malamoeba scolyti Purrini (Amoebina,Amoebidae) und Menzbieria chalcographi Weiser (Neogregarina,Ophryocystidae)

Experimental infection of differentPitygenes chalcographus strains with the protozoan parasitesMalamoeba scolyti andMenzbieria chalcographi were partially successful.Malamoeba, although not yet described as a parasite ofPityogenes in the field, seems better adapted to this new host thanMenzbieria. The development of the two pathogens is comparatively described. Preliminary results on mortality in infected and uninfected samples indicate an influence of nematode infection on susceptibility ofPityogenes toMenzbieria andMalamoeba and strain-specific differences in sensitivity to protozoan infection, as well.     

Costs of protable sawmilling timbers from the acacia woodlands of western Queensland,Australia

Portable sawmilling trials with Acacia aneura (mulga) and A. cambagei (gidgee) have been undertaken to estimate the private landholder costs associated with small-scale timber production from woodlands in western Queensland, Australia. A time study of harvesting and milling operations facilitated estimation of landholder labour input requirements. The scarcity and small size of millable logs, coupled with the prevalence of timber defects, make harvesting and portable sawmilling of western Queensland acacias an expensive undertaking for landholders. The cost of producing sawn timber that meets the High Feature (HF) grade of Australian Standard AS2796 is estimated at between A$3,000/m³ and A$3,400/m³ of HF timber.     

Abiotic factors limiting photosynthesis in Abies lasiocarpa and Picea engelmannii seedlings below and above the alpine timberline

Most research on the occurrence and stability of alpine timberlines has focused on correlations between adult tree growth and mean temperatures rather than on specific mechanisms. Timberline migration to higher altitude is dependent on new seedling establishment in the tree-line ecotone; however, reductions in photosynthetic carbon gain in establishing seedlings have previously been interpreted solely in terms of decreased seedling survival. Our objective was to evaluate the impact of abiotic factors (temperature, light and water) on photosynthetic carbon gain in young seedlings of the two dominant conifer tree species occurring naturally above (tree-line ecotone site, TS) and below (forest site, FS) a Rocky Mountain timberline in southeastern Wyoming, USA. Coincidentally, measurements were made during an unusually dry summer. Mean daily photosynthesis in seedlings of both Abies lasiocarpa (Hook.) Nutt. (subalpine fir) and Picea engelmannii Parry ex Engelm. (Engelmann spruce) was less at TS than at FS (19 and 29%, respectively). Minimum nighttime temperatures below 2 degrees C were more frequent at TS than at FS and were associated with reduced maximum photosynthesis the following day. Low midday water potentials were associated with a reduction in carbon gain at both sites early in the season, prior to snowmelt, as well as late in the season when soils began to dry. However, the lower photosynthetic rates at TS than at FS appeared to be unrelated to seedling water status because seedlings at both sites had similar xylem pressure potentials. Solar irradiance was highly variable at both sites as a result of uneven shading by neighboring trees, although this variation was substantially reduced on cloudy days (44% of all days observed). Compared with sunny days, cloudy days resulted in greater integrated daily carbon gain at both sites (41% increase at TS and 69% increase at FS), based on a simulated photosynthesis model. Photosynthetic responses to temperature, sunlight and water suggest that variable solar irradiance and nighttime temperatures were major abiotic factors limiting photosynthetic carbon acquisition in these young seedlings, especially for seedlings growing in the tree-line ecotone.     

Tenure reform in British Columbia? Model,trust and charter forests

By retaining 91% of the forests in public ownership, British Columbia (BC) holds one of the world’s highest proportion of forest land under a publicsector model for the development and management of the province’s increasingly valuable forest resource. Public ownership implies that critical linkages between the natural forest resource endowment, public-sector management policies and the standard of living of the people of the province are to be forged. Yet, the emerging changes in fundamental public perception of the appropriate use of forests suggests that some of these policies, especially as they relate to forest tenure, are failing to respond to the needs of people in the 21^st century. Some of those linkages require retooling. Although somewhat constrained by past forest activities and policies, the provincial government possesses broad authority across the entire public and private forest system to regulate forest practices and determine rate of cut, stumpage, royalties and rents. It can change the way it does business. It can also devolve responsibility and decision-making to local institutions and create innovative ways of moving toward sustainable forestry. This paper argues that a tenure option developing in the United States — charter forests — may have application in BC and explores briefly how five types of pilots could be tested in the province.     

Untersuchungen über Falterabundanzen des Bekreuzten TraubenwicklersLobesia botrana Schiff. im Weinbau

Zusammenfassung Im Jahr 1994 wurde eine bereits 1993 entwickelte und erprobte Fangvorrichtung eingesetzt, um Fragen zu Populationsdichtebewegungen beiL. botrana zu beantworten. Insbesondere wurden Untersuchungen zur Abundanzdynamik und zur absoluten Abundanz von Faltern beider Geschlechter durchgeführt. So konnten Verschiebungen im Geschlechterverhältnis während der Flugperiode nachgewiesen werden. Ursache dieser Geschlechterverschiebung waren unterschiedliche Entwicklungszeiten der Präimaginalstadien bei Männchen und Weibchen. Berechnungen zur absoluten Abundanz von Faltern der 2. Generation ergaben Gesamt-Falterdichten zwischen 33 und 209 Faltern pro 10 m². Die Anzahl der an Trauben abgelegten Eier je Falterweibchen betrug etwa 30. Für das Verhältnis zwischen Falterdichte und Ei- bzw. Larvendichte konnten Korrelationen errechnet werden. Ein Zusammenhang zwischen der ersten und zweiten Generation hinsichtlich des Massenwechsels war nicht feststellbar. Ein vorläufige Bestimmung der kritischen Falterdichte, die im Zusammenhang mit der Anwendung von Pheromonen zur Paarungsstörung von Interesse ist, konnte vorgenommen werden. Sie lag bei maximal 4 männlichen und 4 weiblichen Faltern pro 10 m².

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Investigations on abundances of the grape mothLobesia botrana Schiff. in viticulture

In 1994 a catching device, which had been developed and tested in 1993, was used for answering questions about population density movements inL. botrana. Investigations were focused on abundance dynamics and absolute abundances of moths of both sexes. Movements of the sex ratio are shown. These movements are due to different developmental periods of premature stages of males and females. Calculations on the absolute abundance of moths of the second generation amounted to densities between 33 and 209 moths per 10 m². The number of eggs laid on bunches of grapes equalled approximately 30 per female. The density of moths and densities of eggs and larvae correlated. Densities of first generation larval populations and second generation moths populations of the pest showed no correlation. A temporary determination of the critical density of moths, which is important for the application of pheromones in mating disruption, was achieved. The upper limit equalled 4 male and 4 female moths per 10 m².

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Mit 2 Abbildungen und 3 Tabellen     

Studies on trapping of Fall Webworm moth,Hyphantria cunea (Drury) (Lepid., Arctiidae)

With the aim of optimizing the trapping ofHyphantria cunea (Drury) males through pheromones, the activity of various traps, doses of pheromone components and dispensers was investigated. The best degree of activity was obtained by funnel traps (Uni-traps) with high capture ability and satisfactory representation of the flight curve when the population of the moth is high. On the contrary, the sticky traps gave good results in low density population. Comparing the activity ofH. cunea to the pheromones, (3Z, 6Z, 9S 10R)-cis-9,10-epoxy-1,3,6-heneicosatriene (or TEP), (3Z, 6Z, 9S 10R)-cis-9,10-epoxy-3,6-heneicosatriene (or DEP) and linolenic aldehyde (or TAL), the results obtained showed different responses according to the areas considered. Blend 1∶1∶1 of DEP:TAL:TEP revealed better results in the Venezia area (north-east Italy), while the activity of the Japanese dispenser (2∶30∶1) was highest in the Novara area (north-west Italy); on the contrary no significant differences were noted in Bergamo, the middle area considered. These results denote that the Italian population ofH. cunea could be made up of different strains, introduced from different geographical areas, with the presence of pheromone dialects.     

The influence of normal and low-rate application of insecticides on populations of the cotton whitefly and melon aphid and associated parasites and predators on cucumber

Studies were conducted in cucumber fields to evaluate the standard and reduced dosage rates of 5 insecticides for control the cotton whiteflyBemisia tabaci (Genn.) and melon aphidAphis gossypii Glov. and effect of insecticide application on associated parasites and predators. Eggs of whitefly appeared to be less susceptibility to all treatments (max. 66% reduction) than larval and pupal stages. Populations of larval and pupal stages of whitefly were significantly reduced in all treated plots. For example (larvae on day 10 after treatment with ethiofencarb, diafenthiuron, and chlorpyrifos methyl 67, 50, and 68% pupae 68, 69, and 75%). Two aphelinid parasitoids,Eretmocerus mundus Mercet andProspaltella lutea Masi, were the most primary important parasitoids of the whitefly pupae in all test plots. Percent parasitism, in most treated plots, were slightly affected as a result of insecticide application. However, all tested insecticides and dosage rates caused severe suppression of emergence of adult parasitoids. Moreover, longevity of adult parasitoids were highly decreased. Populations of the melon aphid were extremely reduced, especially by ethiofencarb and diafenthiuron. Populations of predator species (Chrysopa carnea Steph.,Coccinella undecimpunctata Reiche andSyrphus spp.) were reduced in all treated plots. However, ethiofencarb applied at rates as low as 208.4g a.i./1001 provided equally effective aphid control and conserved numbers of insect predators in the treated plots. Also, the prothiofos and chlorpyrifos methyl applications at rates as low as 166.7 g a.i./1001 kept aphid numbers below than those in control and caused a smaller reduction in the combined populations of insect predators.     

Evaluation of microbial and chemical insecticides for the control ofSpodoptera exigua (Lep., Noctuidae) on soybean plants

Field experiments have been carried out to evaluate the potency of the biological control agentBacillus thuringiensis (Dipel), the pyrethroid Fenvalerate and their combinations for the control of the lesser cotton leafwormSpodoptera exigua on soybeans in Qualubia governorate. Molasses was combined with all treatments to enhance their effectiveness. One spray application with either Dipel or Fenvalerate showed an obvious reduction in larval counts ofS. exigua, associated with a significant increase in the crop yield but in varying degrees, in correlation with the tested dose. Treatments with combinations of both biological and chemical insecticides at the lowest tested doses (62 g ofB. t. +50 ml of Fenvalerate/feddan) showed to be highly potential, and caused 2.8 fold increase in the crop yield. It may be recommended that a combination of both preparations may be used for the control ofS. exigua.     

Ecological studies on parasitism ofEretmocerus longipes Compere (Hym., Aphelinidae) on the whitefly,Aleurotuberculatus takahashi David et Subramaniam (Hom., Aleyrodidae) on jasmine in Fuzhou region of the southeastern China

Experiments on host-stage preference, influence of temperature on parasitization, and the feeding niche ofEretmocerus longipes Compere (Hym., Aphelinidae) parasitizingAleurotuberculatus takabashi David et Subramaniam (Hom., Aleyrodidae) on jasmine were conducted both in the laboratory of Institute of Plant Protection, Fujian Academy of Agricultural Sciences and in the field in the Fuzhou region, Fujian Province, PR China. The results showed that the most preferred host-stage ofE. longipes was the 3rd instar ofA. takahashi. The parasitization rate ofE. longipes was significantly affected by temperature, valuing 4.8% at 18 °C, 27.3% at 23 °C, and 55.1% at 33 °C, respectively. The whitefly immature stages and the parasitoid vertically selected all the layers of jasmine plant as their feeding niches, but the whitefly nymph preferred to gather on the top layer, which was considered as its suitable feeding niche, while the parasitoid selected the middle layer as its feeding niche. To measure the ability to utilize spatial resources, the feeding niche breadth was introduced to demonstrate that the parasitoid had the less wide feeding niche breadth among the all stages tested on jasmine, which revealed that the spatial activity for the parasitoid was smaller than that for any stage of the whitefly. The cluster analysis showed that the feeding niche of the parasitoid was more closely related to the 3rd instar than to any other stage of the whitefly. It was suggested that relation between the whitefly and its parasitoid was not only depending on the host-stage preference but also on the feeding niche similarity.