The onion thrips Thrips tabaci Lindeman (Thysanoptera:
Thripidae) is the major foliage pest in field cultures of onion (Allium cepa L.) and leek (Allium porrum L.) in Austria (Kahrer, 1990, 1998). Economic damage by onion thrips infestation is caused bybot h nymph and adult feeding on green leaf parts. Theyfeed by piercing
surface tissues and suck up the exuded cellular contents.The emptycell s show silvery-white spots on the leaf surface, which are referred to as silver damage. As a consequence, particularly leek plants become unmarketable (Cr.uger, 1991). Besides qualitative losses, quantitative yield reductions in leek (Vierbergen and Ester, 2000) and onions (Kendall and Capinera, 1987) occur as well.