To study the bionomics of western flower thrips (Frankliniella occidentalis) in Slovenia in the open, monitoring of this pest was performed on six locations in the vicinity of the greenhouses using light blue sticky boards. From the data obtained during this investigation - from September 1997 till April 1999 - it was established that the occurrence of western flower thrips in the open coincides with periods, when the air temperature is within the estimated limits of favourable conditions (15 °C - 25 °C). It was found that in districts with the temperate continental climate, the favourable period for the development of western flower thrips is between the middle of May and the middle of September. However, in districts with the submediterranean climate, this period extends from the beginning of May till the beginning of October. In the first districts, the air temperatures are above the lower developmental threshold from the middle of April till the middle of October, in comparison to the later districts where the air temperatures are above the same threshold from the end of March till the middle of November. Therefore it can be concluded that in Slovenia western flower thrips (Frankliniella occidentalis [Pergande]) does not overwinter in the open in the stage of an active adult. For the time being it can be considered as an economically important pest only in greenhouses. Agricultura 2: 1-6 (2003)

Key words: monitoring; Frankliniella occidentalis; environment; overwintering; Slovenia

1. Boissot N, Reynaud B, Letourmy P. Temporal analysis of western flower thrips (Thysanoptera: Thripidae) population dynamics on Reunion Island.- Environ. Entomol. 1998;27,6:1437-1443.

2. Brřdsgaard HF. Frankliniella occidentalis (Thysanoptera; Thripidae) – a new pest in Danish glasshouses. A review.- Dan. J. of Plant and Soil Sci. 1989;93:83-91.

3. Brřdsgaard HF. Monitoring thrips in glasshouse pot plant crops by means of blue sticky traps. IOBC/WPRS Bull. 1993;16(8):29-32.

4. Cabello T, Abad MM, Pascual F. Capturas de Frankliniella occidentalis (Pergande) (Thys.: Thripidae) en trampas de distintos colores en cultivos en invernaderos. Bol. Sanid. Veg. Plagas. 1991;17:265-270.

5. Chatzivassiliou EK, Weekes R, Morris J, Wood KR, Barker I, Katis NI. Tomato spotted wilt virus (TSWV) in Greece: its incidence following the expansion of Frankliniella occidentalis, and characterisation of isolates collected from various hosts. Ann. Appl. Biol. 2000;137:127-134.

6. Chellemi DO, Funderburk JE, Hall DW. Seasonal abundance of flower-inhabiting Frankliniella species (Thysanoptera: Thripidae) on wild plant species. Environ. Entomol. 1994;23,2:337-342.

7. Chyzik R, Ben Dov Y, Nakache Y, Klein M. Association of the Western flower thrips (Frankliniella occidentalis) with cultivated sunflower (Helianthus annuus) in Israel.- Phytoparasitica. 1995;23,2:147-155.

8. Clarke GM, Cooke D. A Basic Course in Statistics. Arnold, Oxf. Univ. Press. 1998;672 p.

9. Del Bene G, Gargani E. Contributo alla conoscenza di Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Redia. 1989; LXXII(2):403-420.

10. Felland CM, Hull LA, Teulon DAJ, Cameron EA. Overwintering of western flower thrips (Thysanoptera: Thripidae) in Pennsylvania. The Can. Entomol. 1993;125:971-973.

11. Felland CM, Teulon DAJ, Hull LA. Overwintering and Distribution of Western Flower Thrips in the Mid-Atlantic United States. Thrips Biology and Management, Plenum Press, N. Y. and Lond. 1995:461-464.

12. Gaum WG, Giliomee JH, Pringle KL. Life history and life tables of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae) on English cucumbers. Bull. Entomol. Res. 1994;84:219-224.

13. Gonzales RH. Injury behaviour of the western flower thrips, Frankliniella occidentalis (Pergande), on deciduous fruit trees in Chile. Rev. Frutic. 1996;17,2:65-72.

14. Grove T, Giliomee JH, Pringle KL. Thrips (Thysanoptera) species associated with mango trees in South Africa. Afr. Entomol. 2001;9,2:153-162.

15. Harrewijn P, Tjallingii WF, Mollema C. Electrical recording of plant penetration by western flower thrips. Entomol. Exp. Appl. 1996;79,3:345-353.

16. Helyer NL, Brobyn PJ. Chemical control of western flower thrips (Frankliniella occidentalis Pergande). Ann. Appl. Biol. 1992;121: 219-231.

17. Herron GA, Cook DF. Initial verification of the resistance management strategy for Frankliniella occidentalis (Pergande) (Thysanoptera:Thripidae) in Australia. Aust. J. Entomol. 2002;41,2: 187-191.

18. Hydrometeorological Institute of Slovenia. Climate of Slovenia (ed. Cegnar, T.).- Ljubljana, Minist. of Environ. and Phys. Plan. 1996:70 p.

19. Immaraju JA, Paine TD, Bethke JA, Robb KL. Western flower thrips (Thysanoptera: Thripidae) resistance to insecticides in coastal California greenhouses. J. Econ. Entomol. 1992;85:9-14.

20. Janežič F. Third contribution to the knowledge of thrips species (Thysanoptera) on plants in Slovenia.- Res. Rep. Biotech. Fac. Univ. of Ljubl., Vol. 71 – Agric. issue. 1993:161-180.

21. Jenser G. Über das Freiland-Auftreten von Frankliniella occidentalis (Perg.) (Thysanoptera) in Ungarn. Anz. Schädlingskde., Pflanzenschutz, Umweltschuzt. 1990;63:114-116.

22. Karnkowski W, Trdan S. Frankliniella occidentalis: Diagnostic protocols for regulated pests. OEPP/EPPO Bull. 2002;32:281-292.

23. Katayama H. Effect of temperature on development and oviposition of western flower thrips Frankliniella occidentalis (Pergande). Jpn. J. Appl. Entomol. Zool. 1997;41,4:225-231.

24. Lacasa A, Esteban JR, Beitia FJ, Contreras J. Distribution of western flower thrips in Spain. Thrips Biology and Management, Plenum Press, N. Y. and London. 1995;465-468. 5

25. McDonald JR, Bale JS, Walters KFA. Low temperature mortality and overwintering of the western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae). Bull. of Entomol. Res. 1997;87:497-505.

26. Ogrin D. Climate. In: Geographical Atlas (eds. Frifl J, Kladnik D, Oralen Adamič M, Perko D.). Ljubljana., DZS:110-111.

27. Rakovec J, Vrhovec T. Osnove meteorologije za naravoslovce in tehnike.- Ljubl., Dru_. mat., fiz. in astron. Slov. 1998;253-258.

28. Rakovec J, Zupančič B, Cegnar T, Sušnik A, Rogelj D, Uhan J, Bergant K, Kajfež-Bogataj L. Spremembe in trendi v Sloveniji izmerjenih meteoroloških spremenljivk in fenoloških količin ter priprava scenarijev spremembe podnebja. Ljubl., FMF, Dep. Phys, Chair meteorol. 1998: 134 p.

29. Schmidt ME, Frey JE. Monitoring of western flower thrips Frankliniella occidentalis in greenhouses. Med. Fac. Landbouww. Univ. Gent. 1995; 60(3a):847-850.

30. Shipp JL, Gillespie TJ. Influence of temperature and water pressure deficit on survival of Frankliniella occidentalis (Thysanoptera: Thripidae).- Environ. Entomol. 1993;22,4:726-732.

31. Smith IM. Glasshouse quarantine pests for the EPPO region and measures recommended by EPPO and the EU to prevent their spread. OEPP/EPPO Bull. 1999;29:1-2:23-27.

32. Tommasini MG, Maini S. Frankliniella occidentalis and other thrips harmful to vegetable and ornamental crops in Europe.- In: Biological control of thrips pests, Wagening. Agric. Univ. Pap. 1995;95(1):1-42.

33. Trdan S, Milevoj L. Influence of temperature, light:dark period ratio and prevailing colour in the immediate environment of western flower thrips (Frankliniella occidentalis Perg.) on the number of its progeny. Med. Fac. Landbouww. Univ. Gent, 2000; 65(2a):363-368.

34. Trdan S, Seljak G, Jenser G. Western flower thrips (Frankliniella occidentalis Perg.) in Slovenia. Lect. and Pap. present. at the 4th Slov. Conf. on Plant Prot., Portorož, March 3-4, 1999, Plant Prot. Soc. of Slov., Ljubljana. 1999;239-246.

35. Trdan S. Colour preference of some economically important Thysanoptera species. Lect. and Pap. present. at the 4th Slov. Conf. on Plant Prot., Portorož, March 3-4, 1999, Plant Prot. Soc. of Slov., Ljubljana. 1999a:493-498.

36. Trdan S. Monitoring cvetličnega resarja (Frankliniella occidentalis Perg.) z barvnimi lepljivimi ploščami. Sodob. kmet. 1999b;32(10):475-480.

37. Van Dijken FR, Dik MTA, Gebala B, De Jong J, Mollema C. Western flower thrips (Thysanoptera: Thripidae) effects on chrysanthemum cultivars: plant growth and leaf scarring in nonflowering plants. J. Econ. Entomol. 1994;87,5:1312-1317. Received September 11, 2002; Accepted in final form February 26, 2003