Aphid populations feeding on common milkweed (
L.) were investigated in seven different sand associations in Hungary during the spring of three years: 2005, 2007 and 2008. In each year the populations of
colonized on the host plant. The experimental fields were selected on the following habitats: an orchard, a locust forest, a semi-natural grassland, an open sand grassland, a plough-land, poplar- and pine-grove clearings. In each year we surveyed the parameters of plant individuals and infestation of plants by aphids. The number of plants did not differ significantly, but the number of aphids showed a considerable difference. The colonies preferred the peak of shoots, the upper levels of plants and adaxial leaf surfaces. The host plant preference of aphids was tested by Spearman’s rank correlation and a Mann-Whitney test. In 2008 there was a heavy infestation on the apical parts of milkweed shoots on the plough-land, therefore many aphids moved to the abaxial leaf surfaces. The apterous forms usually dominated the aphid colonies except two areas of the 2008 year, where the high density of aphids generated alate production. Aphid colonies were attended by different ant species, therefore the aphid-ant mutualism was investigated in each sites.
(e.g., Erigeron annuus ). ₋ Transformer species : invasive species that significantly alter their bi- otic and/or abiotic environment, resulting in the permanent alteration or disappearance of the original vegetation (e.g., Asclepiassyriaca
Diastase and glucose-oxidase activity was determined in 8 samples of Hungarian milkweed (Asclepias syriaca) honey and in 10 samples of Hungarian acacia (Robinia pseudoacacia) honey. The aim of the study was to compare diastase and glucose-oxidase activity of milkweed and acacia honey. Mean value for diastase was 16.28 diastase number (DN) (±2.53) in acacia honey and 24.48 DN (±5.07) in milkweed honey. Mean value for glucose-oxidase was 3.67 nmol unit g–1 (±3.31) in acacia honey and 8.24 (±4.21) in milkweed honey. The differences both in diastase and glucose-oxidase activities of the two honey types were statistically significant.
Sugar composition, pH, invertase and diastase activity and colour of 7 robinia (Robinia pseudoacacia) and 8 milkweed (Asclepias syriaca) honey samples were compared, all purchased from producers and wholesalers. Milkweed honeys proved to be of darker colour and more acidic. The two unifloral honeys showed statistically significant differences between their diastase and invertase activities, milkweed honey showed higher enzyme activity values than robinia honey. The fructose to glucose ratio was 1.58 in case of robinia honey and 1.28 in case of milkweed honey. There was also a significant difference between the di- and trisaccharide content of the two unifloral honeys.
Previous overviews of plant invasion in Hungary were based on local case studies and the authors’ experience. The MÉTA survey provided an opportunity to outline a more exact picture based on the survey of the whole country. This paper summarises the basic statistics related to plant invasion: cover of invaded area estimated for the country, each geographical region and each distinguished (semi-)natural habitat category, and cover of the selected 15 alien species in each habitat category.
Tomato spotted wilt virus (TSWV) is spread by Thrips tabaci tabaci nominate subspecies in the field under climatic conditions of Carpathian Basin. The overwintered females harbouring the pathogen proved to be the most important vector in the outbreak of epidemics in the tobacco growing district. Among the numerous host plants, the winter annual and the perennial weeds provide the survival of the pathogen. Infected weeds as Asclepias syriaca, Convolvulus arvensis grown in vineyards far from the tobacco fields and greenhouses indicate the wide spread of TSWV. Chickweed (Stellaria media) being a suitable host both for TSWV and the overwintering T. tabaci specimens constitutes the most dangerous source of epidemics. As a result of the common effect of the application of insecticides in accordance with the monitoring of T. tabaci, the centralized cultivation of the seedlings and the weed-free surroundings of the nurseries, the occurrence of TSWV was reduced to the minimum level in tobacco fields.
Biological invasion is a crucial problem in the world because of its negative consequences for protected areas. The degradation stage of vegetation might affect the success of invasion. One of the most abundant and threatening invasive species is the common milkweed (Asclepias syriaca L.) which has invaded already 23 countries of Europe and in several habitat types its further spreading is promoted by climate change. Pannonian sand grassland is one of the most threatened habitat by common milkweed invasion. Therefore, invasion in sand grassland vegetation is an important issue. However, the effects of the invasive plant in the open sand grassland are rather controversial. In order to clarify the existing contradictory results, the study was carried out in a strictly protected area, near Fülöpháza (Hungary) in a reserve core area in a UNESCO biosphere reserve. Microcoenological study was applied to determinate the fine-scale community characteristics of non-invaded and invaded stands in natural and seminatural vegetation and data were processed by Juhász-Nagy's information theory models. Shannon diversity of species combinations (compositional diversity) which describes the ways of the coexistence of species, and the number of realized species combinations were used for measuring beta diversity. Differences between stands were analyzed by two-way ANOVA. The maximum compositional diversity of species and main life-forms (annuals, perennials and cryptogams) did not differ significantly between the non-invaded and invaded stands. In contrast, significantly larger characteristic areas of compositional diversity were detected in the invaded stands. Based on these results, it could be concluded that diversity of species combinations did not change but those values have shifted to coarser scales in case of invaded stands. The direction of this change suggests a kind of impoverishment in the presence of Asclepias. Thus, it is worth mentioning from the invasion management point of view that protection of the habitats against disturbance is a more cost-effective and successful way than protection against the establishment or extirpation of invasive species, since disturbance facilitates the invasions throughout the impoverishment of the community.