Thrips in Slovenia

The is an overview of our knowledge of thrips in Slovenia. It includes a check-list of species recorded, indicating the plants from which specimens have been taken and the collectors. Special attention is given to work on thrips during the last five years, focusing on some species of potential economical importance. but in the inner land single specimens can be found as early as March and as late as November. In some Mediterranean countries F. occidentalis can be active in the open all the year round (Lacasa et al., 1995), but in Slovenia it does not overwinter as an active adult. In spite of its massive occurrence in the vicinity of greenhouses during the warm period of the year (while its occurrence further from the greenhouses is rather exceptional) no serious feeding damage was observed (Trdan, 1999; Trdan and Jenser, 1999). This is not the case in some other Mediterranean countries (Klein et al., 1995; Moleas et al., 1996). Thrips tabaci is also common in Slovenia, so it is often cited as an autochthonous species, though there is no proof for that. Its most numerous occurrences are reported in the open, especially on edible onion crops (onion and leek being among the most mentioned and treated host plants) and on some ornamental plants. Because insecticides against this pest are used sometimes too often and not selectively, resistant populations developed and its control can present some problems to the growers. During recent years an increased occurrence of this thrips has been observed on cabbage. On these plants the outer parts of the head leaves develop uneven rough, bronzed areas. Such areas can merge and cover most of a damaged leaf (Trdan, 2001). The efficiency of insecticides against onion thrips and against other thrips species is difficult to study in the open, because these animals are so tiny and hidden. So, lately, laboratory studies are increasingly common. Since the efficiency of an insecticide depends on our knowledge of the bionomics of any given species, monitoring of the Thrips tabaci was performed in the 1999-2000 period. Sticky boards of light 352 THRIPS AND TOSPOVIRUSES: PROCEEDINGS OF THE 7TH INTERNATIONAL SYMPOSIUM ON THYSANOPTERA 353 blue colour were used in onion and leek. In this way, we expect to get useful data on part of the bionomics of this pest in Slovenia; additionally, laboratory studies on its life and development can also be of great use. One rearing method has been developed at the Institute of Phytomedicine (Trdan, 2000; Trdan and Milevoj, 2000). We know that Slovenia, due to its small agricultural acreage, cannot compete with other EU countries if only the quantity of the products is consider, so the importance of environmentally friendly agriculture is becoming increasingly important. Generally, the great majority of farmers will have no serious difficulties keeping to such ways of farming, since the use of pesticides is already quite modest. So we expect various ways of biological pest control will prevail in the future for thrips control (Milevoj, 1998). These have been experimental up to now (Zadravec and Bavec, 2001) and during the last years some biotechnical methods are being introduced also in thrips control (sticky boards of light blue colour) in order to reduce the number of these pests. At the Biotechnical Faculty (Agronomy Department), a project to develop a protocol for molecular identification of economically important thrips in Slovenia was started in 2000. Biochemical and molecular techniques are currently being widely used around the world to detect and identify harmful organisms (Babcock and Heraty, 2000), although thrips have been given less attention in this respect (Kraus et al., 1999). The cooperation with the researchers from the Martin-Luther-University Halle-Wittenberg, Institute of Zoology and from the Leibniz Institute for Plant Biochemistry Haale/Saale (Germany) has been very helpful. The aim of the project is to develop a molecular key of economically important thrips, which could be of use not only for entomologists but also for phytomedicine and biology in general. Conclusions Compared to some other European countries where occurrence and importance of thrips has been given much attention during the last fifty years, most of our knowledge of these insects in Slovenia is based on data from zur Strassen (54 species) or Janežič (44 species), who studied thrips in the beginning of the eighties and in the nineties. The results of their investigations are a good basis for practically oriented investigations of economically important species that have been intensified since 1997. Investigations on the bionomics of some species could help farmers to control economically important species, such as F. occidentalis and T. tabaci, and the development of a molecular identification key will make the world of thrips comparable with other topics of biology (virology, biotechnology, taxonomy, plant quarantine). In the future we also plan to investigate various ways of environmentally friendly control of economically important thrips in Slovenia. Acknowledgement The author thanks prof. dr. Gábor Jenser for his help in the beginning of my work with thrips and for other useful information in connection with these interesting animals, Bert Vierbergen for the idea to prepare the check-list of thrips in Slovenia and dr. Richard zur Strassen for the revision of the check-list and for his permission to publish his data about the fauna of “Slovenian” thrips.