Functional analysis of vegetation on alpine treeline ecotone in the Julian and Kamnik-Savinja Alps in Slovenia

Our study focused on the functional aspects of plant species and vegetation at the transition from larch (Larix decidua Mill.) forest to mountain pine (Pinus mugo Turra) stands on the alpine treeline ecotone. With increasing elevation, living conditions grow harsher, which is reflected in the plant species and functional trait composition of plant communities. At four different localities in the Slovenian Alps, relevés along an altitudinal gradient and according to vegetation type were made (European larch forests, larch trees-mountain pine shrubs, mountain pine shrubs), using standard Central European phytocoenological method. In the upper mountain pine belt, few differential species were found, since most species represented in mountain pine stands also occurred in the lower two vegetation belts, while there were many differential species in the lower forest belt. Species with considerable competitive ability and moderate stress tolerance dominated the upper treeline ecotone, whereas ruderality is poorly expressed. The importance of stress tolerance in plant strategies increased slightly in the mountain pine belt. Changes in the representation of some functional traits attributes were detected by vegetation belts, but complete species turnover did not occur. Changes in dominant life form involved greater cover of chamaephytes and nanophanerophytes in the upper mountain pine belt. Species with evergreen leaves dominated mountain pine stands and deciduous forest stands. The share of species with scleromorphic leaves increased in the direction of the mountain pine belt while the share of species with mesomorphic and hygromorphic leaves declined. Mountain pine stands create good conditions for the regeneration of tree species and colonisation by ecologically more demanding forest species while species of alpine grasslands withdraw on open areas. Since today’s treeline is lowered due to past human activity, an upward shift is expected. Also, considering the great importance of competition strategy, current conditions in mountain pine stands are favourable for future forest succession.     

Evaluation of spinosad for the oral treatment and control of flea infestations on dogs in Europe

The novel ectoparasiticide spinosad is a naturally occurring mixture of spinosyns A and D formed during a fermentation process. The spinosyns are tetracyclic macrolides with a unique ring system. Their mode of action differs from that of other commercially available insecticides. Laboratory and field trials were conducted to evaluate the use of spinosad in a chewable tablet at a dose range of 45 to 70 mg/kg for the treatment and control of flea infestations on dogs in Europe. Laboratory studies with artificially infested dogs confirmed persistent activity against Ctenocephalides felis of higher than 99 per cent at three weeks post-treatment with values of 96.5 to 97.8 per cent at four weeks. Two multicentric field trials with naturally infected client-owned animals in five European countries used selamectin as comparator. Monthly doses were given during the summer when many homes were heavily infested. Households with spinosad-treated dogs showed cumulative benefits with flea burdens reduced by about 97 per cent at 14 and 30 days and by 99.6 per cent at 60 and 90 days. Corresponding figures for selamectin were significantly lower (P<0.05) at all time points: between 88.5 and 91 per cent at 14 and 30 days, then 97.8 and 98.2 per cent at 60 and 90 days. Thus, the performance of spinosad compared favourably with that of the established reference product.     

Determination of selamectin in dog plasma by high performance liquid chromatography with automated solid phase extraction and fluorescence detection

A method is described for the determination of selamectin in dog plasma, using High-Performance Liquid Chromatography (HPLC) with fluorescence detection (excitation and emission wavelengths fixed at 355 and 465 nm, respectively). The fluorescent derivative was obtained by condensation reaction with trifluoroacetic anhydride and N-methylimidazole. The method employs 1 mL plasma samples and gives linear calibration graphs (r = 0.999) over the concentration range studied (0.5-50 ng mL(-1)). Automatic solid phase extraction using the benchmate procedure was used for sample preparation. This method permits the determination of selamectin at levels as low as 0.1 ng mL(-1) and its suitability was demonstrated by a pharmacokinetic study on a dog receiving the therapeutic dose (Spot-on administration).     

Post-harvest chemical treatments for control of tuber infection byAlternaria solani

Post-harvest application of several chemicals, including captan, sodium hypochlorite, chlorine dioxide, triphenyl tin hydroxide, captafol, and iprodione signficantly (P=0.05) reduced infection of potato tubers (cv Norchip) byAlternaria solani. Application rates of 5.4 or 8.3 1 of chemical mixture/metric ton were effective although limited evidence indicated that the higher rate may provide additional control. Post-harvest treatments appeared to be effective when disease pressure, as measured by the numbers of lesions per tuber, was low to moderate and seemed to lose effectiveness when disease pressure was high. It is suggested that routine post-harvest applications of effective chemicals coupled with proper storage management in disease prone locations might be an economically feasible way to control early blight losses in storage.     

Elevated concentrations of T‐2 toxin cause oxidative stress in the rainbow trout (Oncorhynchus mykiss)

T‐2 toxin is a mycotoxin produced by several Fusarium fungi that can contaminate plant components used in feed for aquaculture. The aim of this 28‐day study was to investigate the effect of the T‐2 toxin in feed in concentrations 1.0 and 1.8 mg/kg (0.01 mg/kg b.w. and 0.018 mg/kg b.w.) on the oxidative stress markers and on the detoxifying enzymes of the rainbow trout. The results showed that T‐2 toxin in both tested concentrations induced oxidative stress and antioxidant defence in the liver of trout manifesting by the increase in activities of enzymes glutathione‐S‐transferase, glutathione reductase and glutathione peroxidase and the decrease in the catalase activity. The increase in lipid peroxidation was recorded only in the higher concentration of T‐2 toxin. Ceruloplasmin activity in the plasma increased at both tested concentrations, and the ferric reducing ability of the plasma increased at the higher toxin concentration. The T‐2 toxin in feed caused alteration of the total protein, albumin and triacylglycerols as well as the alkaline phosphatase activity in the plasma. Despite no changes in histological examination were found, the influence of T‐2 toxin on scavenger system may result in increased sensitivity to other stress factors.