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The occurrence and host range of Tomato spotted wilt virus (TSWV) was investigated in Central and Eastern Europe. The relationships among the TSWV, the vector species and weed plants were surveyed.
The available data referring to the occurrence and geographical distribution of the females and males, the host range, the virus vector capability and the monitoring of Thrips tabaci Lindeman, as well as susceptibility and resistance of cultivars of some cultivated plant species are discussed.
Eight Hymenopteran parasitoids: Itoplectis alternans (Grav.), Itoplectis maculator (F.), Pimpla spuria Grav., Diadegma apostata (Grav.), D. longicaudata Horst., D. tenuipes (Thoms.), D. holopyga (Thoms.) and Dibrachys cavus (Walk.), and one hyperparasitoid Gelis areator (Panz.) have been reared from the larvae and pupae of the grape moth Lobesia botrana (Denis et Schiffermüller), collected between 1996 and 2003 in two wineyards of southern Romania. Nine host-parasitoid relationships have been recorded, from which seven are new for Romania and the other two new to science. The role played by these parasitoids in the regulation of the host populations is 12.3%. Diadegma longicaudata Horst. is the most important member of this parasitoid complex with a parasitizing ratio of 7.75%. The parasitism of hibernating stages is more important than the summer ones, both in percentage (24.2/8.94%), and in species diversity (6/1). The small number of species and the low values of aestival and hibernal parasitizing are the effect of intensive chemical treatments in these vineyards.
Yellow proved to be the most reliable colour for monitoring of Thrips tabaci. White and blue could be used with weak, but still reasonable effectiveness.
Thysanoptera species were collected from Stellaria media in autumn, winter and spring in different biotopes, in Hungary. The total number of the sampled specimens was 5121. The most frequent species were (in order of frequency): Thrips tabaci, T. atratus, Frankliniella intonsa, Aptinothrips rufus, T. minutissimus, T. nigropilosus and Anaphothrips obscurus. The number of species as well as the composition of the species occurring on S. media depends on the characteristics of biotopes. The number of species considerably increased in spring from 15 to 43. Among them seven species occurred from autumn through winter till spring. S. media provides a suitable site for winter refuge, and an alternative food source for a few species, which hibernate under bark, fallen leaves and dry grass as well as in the soil, leaving their winter quarters move and accumulate temporarily on this plant. Specimens of T. tabaci capable of harbouring tomato spotted wilt virus occurred in every investigated biotopes.
By the sampling on chickweed ( Stellaria media ) carried out from autumn till the end of spring, the occurrence of the larvae of 12 Thysanoptera species has been established under climatic conditions in Hungary. Only the larvae of T. atratus and T. tabaci were present in this period in relatively high number. Since chickweed is frequently infested by Tomato spotted wilt virus (TSWV) the continuous presence of the larvae of T. tabaci in the whole period is a notable circumstance. This relationship is one of the significant ways of the survival of tomato spotted wilt virus which might be a source of new epidemics.
The Fabaceae species Lathyrus tuberosus, Vicia species and Coronilla varia, all of which have an extended flowering period, provide the larvae food and shelter long enough for the pea thrips Kakothrips pisivorus to complete its development, and to have two generations yearly. Although flowers of pea cultivars also confer suitable conditions for egg laying, their flowering period is rather short. Therefore, the larvae are forced to move to developing pea pods in damaging numbers, resulting in the development of only one generation yearly on pea. However, specimens of K. pisivorus are able to colonize pea cultivars that have a similar phenology as Lathyrus tuberosus. Here we show that Hungarian pea thrips populations having either one or two generations are genetically identical.
About 2500 arthropod species immigrate, or carried by wind, or introduced by man in the orchards, under Hungarian climatic conditions. However, the number of the apple pest species is approximately 30. Owing to the effect of the relationships among the plant-phytophagous-zoophagous species those could colonize the orchard for which the apple provides suitable food sources and whose populations are not regulated or are regulated by a weak efficiency by parasitoids and predators. These populations create the primary pest communities. When the individual number of the parasitoid and predator species is reduced by the broad-spectrum insecticides, the population density of those phytophagous species could increase whose populations was restricted up to that time. In this case the secondary pest communities could develop. The integrated pest management provides the possibilities to solve the problems caused by the regular use of broad-spectrum insecticides. The real requirement is to find and to harmonize those methods which regulate the population dynamics of the species of the primary pest communities.
Specimens of Thrips tabaci Lindeman were collected on numerous plant species in the Hungarian National Parks as well as on ruderal vegetations, but no males were found. At the same time both females and males occurred on the following cultivated plants: on tobacco (Nicotiana tabacum), potato (Solanum tuberosum) and onion (Allium cepa), as well as on weed plants as Galinsoga parviflora, Datura stramonium, Stellaria media. Only thelotokous populations were observed on cabbage occurring frequently in high individual number. The ratio between females and males continuously changed during the vegetation period. The occurrence and host range of the studied arrhenotokous populations do not confirm the existence of the subspecies Thrips tabaci tabaci (arrhenotokous) and T. tabaci communis (thelotokous), nor the correlation between the longitudinal occurrence of males and the physiological factors existing inside the Allium plants.
The LIFE 02ENV/RO/000461AIR-AWARE project is partly dedicated to research on the flora and invertebrate fauna of downtown Bucharest (Romania). In this area, products of local industrial pollution, heavy metals, SO 2 and powders in suspension exceed standard levels. The pilot zone is represented by two public parks in downtown Bucharest. Thysanopterological samples were collected from the herbaceous layer, on both weeds and ornamentals, following a transect approach. The preliminary results revealed a biodiversity that decreased from the park centres, which suffered the least air pollution, towards the edges of the parks, which were the most polluted. The dominant species was Frankliniella intonsa , which had high values for structural and functional indices, as well as morphological changes in body size, colour and antennae, all due to the air pollution. F. intonsa could be considered to be a very sensitive bioindicator of environmental pollution. Future analysis, however, may reveal whether Bagnalliella yuccae, F. intonsa or Haplothrips niger are more sensitive bioindicators for air pollution.
